Coolant Bottle greatest secrets revealed?
 

UPDATE: You can read the thread, but most of us have come to the conclusion that the magnetic float looses buoyancy over time. Cleaning the bottle may help for some period of time, but the bottom line is.........long term, you either buy a new bottle, or just unplug it and check your coolant level when you check your oil.

Actually, I just found a service bulletin that confirms the float!

See the pdf attached at post #134(if that number doesn't change) I posted it on 1/22/2011, or just follow this link..........

https://www.rx8club.com/showthread.p...56664#poststop

or Ash8's post in this same thread which goes into a little more detail about the bottle choices and history!

https://www.rx8club.com/showthread.p...57011#poststop

Special Warning: Have seen a lot of people breaking the plastic nipple of the radiator when changing out the coolant bottle, thereby causing them to have to buy a new radiator. One way to avoid this is to cut the hose at the nipple and avoid this situation!

Maz I just included a pic on the 'Nipple' situation in your first post, I hope you don't mind ASH8

https://cimg3.ibsrv.net/gimg/www.rx8...3b16ffebfe.jpg

Now..............on to the thread and you'll see how the conclusions came about if you are truly bored out of your skull!


So.............after dealing with the dreaded coolant sensor and light for a few months going off and on(usually after spirited driving) like everyone else, I finally decided to go ahead and get a new coolant bottle.

After taking the old bottle out and installing the new one, I played around with the old bottle/sensor and it will in fact pop right out of the bottom of the bottle after taking the entire bottle out! :SHOCKED: See pic 5 for the clip locations. I hacked my way into this bottle as you will read, but you can get the sensor itself out, but there isn't really a need to do so..........read on!

I butchered my old bottle for this experiment. I wanted to get at the float and the float shaft, that's why you will see this piece of the bottle cut out! Pics 1 and 2 are just of the sensor itself and this was after I decided to go further and hack the bottle apart.


All this sensor itself really consists of is two wires running from the plug to the sensor through the plastic plug that connects at the bottom of the bottle. You can see some of that plug(so to speak) in pic 1.

The sensor itself is a small reed switch enclosed inside a small glass tube.

Again............pics 1 and 2, notice the reed switch is not closed at this time.

This sensor(reed switch) slides into a plastic tube when you install the plug/sensor assembly into the bottle(pics 3, 4, and 5 have it installed in the plug and therefore in the shaft/tube). There is a round magnetic float that surrounds the plastic shaft in which the sensor sits and this floats up and down with the coolant level(same pics.....3 through 5). When the coolant level is to low, the magnetic float rides lower on the shaft(pics 3 and 5) and if low enough it causes the reed switch inside the shaft to close, thereby illuminating the idiot light. BTW, the resistance of this switch is about 10 ohms when closed.....keep this in mind.


So...............I assume that the PCM/ECU sends out a voltage on one leg and reads the other leg every so often to determine if the switch is closed or not. This could happen all the time or it might query it every so often(not sure), but either way.............if the coolant is low enough, the magnet falls and the switch is closed.

Having said all that, and remembering how this usually start to fail......getting on it hard usually causes the light to come on and then as you back off, the light will go off. This along with the fact that this goes on for awhile until eventually the light stays on all the time, no matter if you have enough coolant or not, or how you are driving........something eventually fails. (See pics 4 and 5)
Correct me if I'm wrong here, but the spirited driving effect must mean that more coolant is being sucked out of the bottle when getting on it(or possibly a big increase in heat inside the bottle?....see below) and once you back off, the coolant level returns to the bottle(or heat goes down...see below) and the light goes off.................this is of course, until it sticks or fails for good!



I see a couple of possibilities, but think I can eliminate a few real quick.

1.) It's possible that the contact resistance of the reed switch itself could increase over time enough to where the PCM/ECU doesn't like what it sees for the voltage being returned and no matter what the float does, it's stuck or it thinks it's closed. <--- Nope not the issue
The reed switch is enclosed in a glass tube and assumed to be air tight, so I doubt this switch could be sticking or building up much contact resistance. I did throw a meter on the one I took out and slid the magnet up and down and I could see(and measure) the switch open and close. It went from approx. >2meg to 10.0 ohms when it closed.
Worth noting............if it was metal fatigue on the switch contact arms, you think it would be more prone to staying open anyway as opposed to not being able to be closed by the magnet float. <--- Nope not the issue

2.) The plastic shaft that the sensor sits in and that the magnetic float rides up and down on could swell with heat and keep the magnet from sliding freely even when enough coolant? <--- Nope not the issue

Examining the plastic shaft and the distance between the shaft and magnetic doughnut float, the gap is big and the plastic is pretty thick. It would have to expand a whole bunch and cool down real quick(shrink) in the time I've noticed it takes it to go back off.

3.) Look at my pics on the next post and while I didn't show pics inside of the bottle itself, you can see I had crap on where the magnetic float comes to rest(with low coolant level) and it was also on the inside bottom of the tank. I think it's the crap that builds up in the bottle and at the base of the float shaft as coolant gets older that might possibly cause the float to stick. This is why banging on the bottle might dislodge the stuck magnet float and cure it for some period of time. <--- Still possible as cleaning helps but doesn't cure

If I didn't miss anything(and I probably did)..........I think the real solution here is kind of the obvious one.

Change/Flush out your coolant level every year.

Take a look inside the bottle and if you see crap down there, go ahead and take the bottle out and clean that crap out.

See next post!

BTW........It was pouring down rain this morning, so I did experiment with the piece I cut out and you'll see that in the pictures below.
I sprayed contact cleaner on it to hopefully get rid of the crap, then flushed with water.........this didn't remove it.
I didn't want to rub obviously because if it was still in the bottle, you wouldn't be able to get to it!

I let it dry and then hit it with WD-40(again no rubbing) and rinsed with water and you can see the result in the last pic.............it did take it off.

Of course you can't do this with it in the car (and wouldn't want to!!!!!!).........and WD-40 might not be the best to use(remember I wasn't going to reuse this bottle or piece!). If you remove the bottle from the car, and find something that will dislodge that crap and get it loose(even a good stream of water) you'd be in business. The piece I cut out(the magnet/sensor shaft) is located on the left side of the bottle when looking inside from the front of the car and behind a couple of channel slot openings. It might be hard to get to it with any real stream of water. That's why I'm thinking of finding something that will loosen it up on contact, but not hurt the plastic and then flush it out really well with water, let it dry, re-install, and add NEW coolant!


Of course, you could always just
1.) Buy a new bottle. (I did after only ~20k miles)
2.) Unplug the connector. Just check your coolant level often.
3.) Take it out and clean it the piss out of the bottle!

Why doesn't someone sell just the sensor instead of having to buy a whole new bottle? :mad:

Great stuff. Thanks Mazurfer for this very much needed thread.
I have the coolant light issue. On Second bottle and was going to get a third. Now I'm going to try this and see what happens. I'll let you know.

There's a million and one threads on this subject, but I don't think there is one with as much detail.

I hope I was clear.................don't remove the sensor, remove the entire bottle. Even if you are going to attempt to clean and flush, there is no real need to remove the sensor itself. Flush it out really good and get all that crap outta there, however you decide to do that????

What breaks up old crusty coolant? WD40 works, but not sure you should use that!

Concentrate on the area where the float is.......it will be hard to get to from the filler cap opening, but is obviously more important in that area than the rest of the tank.

I figure next time, I will use something to break the crap/crud up, then start flushing with water while shaking the piss out of the bottle until I get all the crap out.....either that or just friggin buy another one! :dunno: :evil_laug


Here's the piece of the puzzle I am struggling with:

If the switch is open(magnet float riding high indicating good coolant level and no light) and magnet falls with low coolant(closing the switch and illuminating the light), then why would unplugging the sensor cause the light to be on(it would be an open circuit)? Hmmmmm.........this kind of tells me that the PCM is looking for a given range of voltage on the return(not completely an open circuit.......ie....infinite ohms), but expects some range of resistance(say 10 ohms to ~2m or so)..................and will illuminate the light if outside that range, either low(magnet) or high(unplugged). Remember when I measure it without the magnet being there, I still read about 2m(if I remember right?)........and it was dropping. I don't remember where it stabilized cause I didn't care, as long as it didn't drop
all the way to 10 ohms and it didn't.
So knowing this info, it should therefore be possible to find the right value resistor and just plug it in to where you disconnect the sensor and you'd have no light. You would however have to check your level and not depend on that light ever coming on. I'll see if sometime in the coming days I can figure out what that value should be, but anywhere greater than 10 ohms and below ~2m might do the trick.

UPDATE: I was going by what some had told me in that unplugging the sensor caused the coolant light to come on. That is not the case in my car(an 05) and if yours does.....I think you have another issue. This is a simple switch. If the float magnet gets too close to the reed switch(low coolant) or is stuck, then you will ge the light. Unplugging the sensor should NOT give you a light as far as I know.

just curious, is it possible for the magnet to slide off the top of the post or is there something to hold it on?

Excellent question! Wow........that could suck!
Well, I didn't see anything that would hold it on, but I'll have to go examine the bottle where I cut it out to make sure. I will assume that the round part at the top of the shaft would fit into something or be close enough to not allow the magnet float to come off, but I'll go look!

thats a good question

Nope..........it can't come off.
For lack of better terms, the shaft that the magnetic float goes around(and rides up and down on), fit's into a receptacle when the assembly is plugged into the bottle, therefore the magnet can't come off.

some info on the bottle..hope to use this for a future refrence

Well, looks like I got some more research to do because I was just poking around on the net and it's possible that this magnetic float is actually Engineered in terms of buoyancy to this specific application. This could throw into the fray that it might be less buoyant in old coolant and possibly different using water, water wetter, or anything else besides what it was Engineered for. It's also possible for the buoyancy of the material to change over time. I just read that depending on the material used, it's possible for these floats to absorb fluid over time and that would change it for sure and also change the temperature coefficients which could/would effect buoyancy.
If any or some of this is the case, then there is no way to get at the float. You can get the sensor out, but you're not getting that float out without hacking into the bottle. Now thinking if it's not the crud build-up causing sticking then cleaning may or may not help! Argh!

Damn those Engineers...........and I is one! :cussing:


This is probably why we are up to revision "M' on the bottle. They probably made it far more complex than it needed to be and can't figure out(or be bothered) to discover what it is that's failing :scratchhe Guess engines are more important than a $160.00 bottle! :crazy:


BTW................when I ran downstairs and into the garage to answer Nuke's question above, I grabbed the float, put it in a pan of water(not coolant) on the stove and it sank to the bottom. The buoyancy does change as it heats up though and it started to become more buoyant and almost floated, once I saw that I just turned off the stove. Probably would have been even more buoyant in hot coolant! :rolleyes: Probably Engineered specifically for FL-22 :wallbash:


My head hurts now, I'm going to have lunch!

Uh....It doesn't ... for me at least. I started getting the light and just unplugged the sensor. Haven't had the light since. :) Mine is a 2005.

Very nice write-up Mazurfer!

Does the glass bulb appear to have fluid in it?
If so, you might have a small amount of current flowing through the liquid (think back to science class with the salt water) that will give you a large resistance.
When the float drops and the contacts touch each other, you'll then have little resistance.
This could explain why the light stays on when you disconnect the harness.
You need to have some kind of "feedback" or resistance to the PCM.

Easy way for you to try it out is to measure resistance with no float installed.
If your meter reads its an open circuit, then I'm wrong with my theory.
If you do measure resistance, then you have current flow even through the contact are not touching each other.

Nicely done mazsurfer! Scribed for quick reference :bigok:

That weird........and to be honest, I haven't tried unplugging it myself. I was merely using others peoples observations that unplugging the sensor caused the light to come on.


EDIT: Neither does mine! I was just going by what people said........that it came on when they unplugged. :dunno:

See below for my further analysis. :eek:

for some reason, I never got any problems with coolant level sensor. I replaced my last one cuz the tab is broken.

Yeah, I thought about all of this. Right now, It would appear as the glass bulb doesn't contain fluid, but it might. I need to take a closer look at it. I did measure it without the float anywhere near the shaft/sensor(it was completely off) and I still read about 2m........so there may be fluid in there. If there is, it is completely filled and there is no air what-so-ever.
I'll examine more closely and double-check readings.

Good observation........it is infact bent! :SHOCKED:
I'm not sure it could catch as there is about 1/16 of an inch gap.........but I did realize it could be a possibility. I have to assume the shaft is straight when new, and nothing I did in removing it caused that bend, so...........................:Wconfused


The analysis will continue!

Yeah, but from what I know, you're pretty anal about changing fluids, so tell me on that old bottle, how often did you change/flush out your coolant? I wondering if "old" fluid effects the bouyancy of the float in some regard and then other things happen.

yeah ... im pretty crazy about changing fluids ... I change my coolant 3 times this year ... LOL

Coolant was on sale man ~~~ it was like 7 bux for Prestone 100% coolant, went to the supermarket to get a gallon of distilled @ 99 cents each ... lol

Anyway, there's always some "crap" sink to the bottom of the coolant bottle,


everytime I flush my coolant, I will take the bottle out, put some dish washing soap & water in there and leave it overnight(or couple hours, depends on when I start the flushing) then I will flush it like 20 times to make sure its clean (no more soap)

:SHOCKED: Wow! :cwm27:

That reminds me..........I need to flush mine!

If the bulb doesn't have fluid in it, it could also be using the same principles as a smoke detector.
A small amount of radiation is used to allow current to flow through the air.
If you're measuring resistance and the two tabs aren't touching, something is in the bulb to allow current to flow.

i've changed mine so many times the plastic drain screw is stripped. I have a hell of a time opening it now.

I guess I could go to the dealer and pay $50 for a plastic screw replacement...

Shhhhhhh

I dont want people from "Green Peace" to know what Im doing ... :Drooling_

Okay, finally got around to doing a little more with this coolant bottle and sensor.


Ash8 may not like this, but this reed switch is a normally open(NO) switch. When the magnet comes in close proximity to the reed switch......it closes!
It's nothing fancy as I was thinking in a previous post, it's just a simple open or closed switch after all.


Here's what I did today:


1.) Start car and verify no coolant light on the dash. I have a new bottle and proper coolant level, so this was of course expected. :wiggle:

2.) Car still running and unplugged the coolant sensor...........this produced no light. This is contrary to what I was lead to believe by several people, but I had never tried it myself. Again...........the unplugged sensor gave no light! Yours could be different, but I don't know why it would be? :dunno:

3.) With it unplugged, I measured the resistance on the "good" coolant bottle end of the connector and it read infinite ohms. The switch was open meaning I had adequate coolant. :ylsuper: This is the same reading I got on my butchered one with the magnet away from reed switch.

4.) With it still unplugged, I then measured the PCM side of the connector and got 14.2v to GND on one leg and nothing on the other. Remember.............my car was still running, so that's why 14.2v and not 12.0v. :scratchhe

5.) Next, I took my old sensor from my butchered up coolant bottle, slid the magnet off the shaft(meaning it would be floating.......as if in the bottle), plugged it in and there was no coolant light on the dash. :icon_tup:

6.) Walked around under the hood, took the magnet and slid it down to where it would be sitting if low coolant or possibly stuck. This of course produced and instant low coolant light. :SHOCKED: :icon_tup:

7.) For the sake of argument, I repeated #5 and #6 about three times just to make sure. :suspect:



So......................I believe you can get a low coolant light for the following reasons.

a.) Your coolant is low.
b.) The shaft that the magnet rides up and down on has been bent by heat and therefore the magnet tends to stick. <----- Still unlikely IMHO
c.) Crud buildup in the bottom of the coolant tank and gums up the magnet and shaft so that it won't float freely and sticks.
d.) a faulty reed switch in the sensor that has stuck closed. <----- Not sure how likely this would really be.

Now.............as some have reported getting a coolant light even with the sensor unplugged. I would have to say that you have some other issue like a short or something in that wiring somewhere. :scratchhe

If you have the low coolant light and don't want to replace the bottle, then you can just unplug the sensor and check your coolant often. I think I would wrap the PCM side of the connector that will be dangling with electrical tape or something in order to keep it dry(and keep crud out) because if the two terminals or wiring short on that side, you are going to get a coolant light.

Thanks for the update Mazsufer :bigok:

Nice job Mazurfer! :biggthump

Ah, it depends on how you view it...this is a Normally Closed "Switch" is made of TWO Parts...the Reed and then the Magnet, without either the "switch" is useless.

So this is classed as a Normally Closed switch.

Without the Magnet the REED is Open, with Magnet the reed is closed, is is NC..;)

The PCM is reading resistance..

I can post a pic of a House Alarm NC Switch...almost identical and for 12-14V use.

BTW, who is arguing...Dave??

Naturally if you slide the magnet LOW enough (as in low coolant) the REED Switch Opens, causing a Coolant Light..

The PCM is reading resistance, because if one "Normally" unplugged the Plug, you are opening the circuit ..ie.. like the reed switch, but you are not seeing a dash light.

So the PCM is reading resistance, as a REED Switch is either Closed (Normal with magnet) or Open when magnet moves far enough...there is no in between, it is at a point where the magnetic field (Float magnet) is far enough from the reed to Open the Two REED strips...Opening the Switch or circuit.

:Peace::wavey::Peace::wavey::Peace:

Well Dave, my past life is also a Home Monitored Alarm system licenced installer, Made in Australia by Clipsal, I have fitted hundreds, the Magnetic REED Switches that we (I) install above Door and or on Widows, so when a intruder OPENS the DOOR or Window, the magnetise part (usually installed on the "moving object") OPENS the REED Switch, so it Opens the Circuit, triggering an Alarm or in this case a Coolant Low warning....in the "trade" these switches are known as a NC one, Normally Closed, which it is when the TWO parts are together..

Here is a pic of an ALARM REED Switch I have 6 in fact and they all the same, the exact same design principal as the Mazda Coolant switch..
Sorry, the pic is Blurry but you will have to trust me without the Magnet the Two REEDs are Apart, with the magnet the reeds are closed (completing the circuit).

The 'Clipsal' Reed Switch REEDS are much closer together in distance apart when the switch is Open. When a magnet (the other part you see) is moved closer there is an "Audible CLICK" when the two metal strips touch or come together..creating a Normally Closed switch.

I repeat these switches are classed as NC because the "Magnet" is part of the Switch.
It is not separate to the switch, when you purchase the reed switch the two are a pair.

They can not be classed as (NO) Normally Open because the Magnetic Round Float "Closes" the reeds, so the switch is NC.
That is the "Normal Position of the Switch"..not the other way around...sorry Dave you are wrong here.

:)

https://www.rx8club.com/attachment.p...1&d=1260154313

BTW: This house alarm Reed Switch also operates on a 12V Powered Systems (transformed down from our normal 240 Volts) , along with PIR's or Passive Infrared Detectors, Key Pads, Main Circuit Boards and Sirens.

I will try and get a better pic...sorry it is a shocker!

Hang on Dave.....
From your own pic of the REED without a Magnet near it you can plainly see the REEDS are Apart, Not Closed, yes?..
https://www.rx8club.com/attachment.p...7&d=1253377138

OK, so as you are the one who has taken this float mechanism apart (thank you BTW), this REED part must be located to-wards the bottom inside of the tube or tank??

I see.... this magnet is probably a very weak one, it floats at the top with coolant, as coolant lowers the magnet then closes the reeds, (and would answer another thought I had), based on the 12V REED Switches I install the Magnet Closed the Reeds Full time. When it Opens or Magnet moves away reed open and triggers light or alarm.

What did not make sense for me was the fact that if you disconnect the Coolant Bottle switches power plug most were not getting a dash light....becasue normally with an NC switch as soon as ANY parts of the Circuit is Open or cut this will trigger a warning or light..

So yeah this makes more sense now...and it also demonstrates Mazda's issue
with these coolant tanks.

Sorry Dave, Please accept my apology, in this case this type of Reed switch is NO.
Normally Open...but IMO it does not make ANY sense.

I am now wondering WHY Mazda have made this circuit this way?.
The unreliability of the the outer tube warping because of heat and then possibly jamming the Magnetic Ring.

As I see it is is a heat issue, the RX-8's and other cars here (Australia) have to have Headlamp Washers if you have HID lamps (it is a design rule law), our tanks have a float and warning lamp and I have not heard of issue with these Cold Water/Fluid Reservoirs.

SO, yes it appears in this case the Mazda switch is NO., and explains a lot to me why owners who disconnect their plugs are not seeing a dash light, because if the switch was NC (like the house ones I fit), a un-plugging should set off a dash lamp or warning.

IF guys are saying they are getting a warning lamp when they unplug, then this does not make any sense as ALL the Replacement Coolant Tanks fit ALL RX-8 models...the latest Update tank with fit a 2003/4 model RX-8.

So I can't understand why they are seeing a warning lamp, this is another reason why this issue confused me Dave and led me to believe what I said.

Any thoughts as to why some RX-8 owners are seeing a dash light when they unplug?

Edit...I should un-plug my 09 Coolant Tank and see what happens, but they use the same tank as the Series I's?..

Dave...

Here is an Oz website link on REED Switches, note how they say they are NC...Not NO..

http://www.swintech.com/reed_switches.htm

The first two Surface switches are the ones I install and have a pic of above..

There is one 'NO' shown...that is because there is no magnet...;)

In any reed switch with a magnet they are classed as a NC switch.

Jon, the Reed Switch Glass does not have any fluid inside, the reeds are made and cased with hermetically (air tight) sealed glass.
The REEDS are De-activated Rhodium.

Here is a Reed Switch, these contacts are actually OPEN, I know it does not look like it but they are ,and is the same distance open to the ones I have here, I would say about 1 to 1.5 mm.

https://www.rx8club.com/attachment.p...1&d=1260159225

I think they do..........it can't hurt anything if you do.

It's all semantics Ash..............From one encyclopedia.

The reed switch is an electrical switch operated by an applied magnetic field. It was invented at Bell Telephone Laboratories in 1936 by W. B. Ellwood. It consists of a pair of contacts on ferrous metal reeds in a hermetically sealed glass envelope. The contacts may be normally open, closing when a magnetic field is present, or normally closed and opening when a magnetic field is applied. The switch may be actuated by a coil, making a reed relay, or by bringing a magnet near to the switch. Once the magnet is pulled away from the switch, the reed switch will go back to its original position.

^..................yep, that's a NO switch. It's open until you bring a magnet into play, then it closes. :beer05: :beer05: :beer05:

I understand how a float/reed switch works, I was just trying to figure out how some people would receive a "low level" light after the harness was disconnected.
My assumption was fluid in the bulb was conducting a small amount of current as "feedback", but you guys mentioned it doesn't.
Only other way is a short... possibly in the harness.
Oh well... a lot of good information here guys :)

Yep, the 09's~ have the same tank, mine has the N3H1-15-350J which supersedes to a L, which then goes to an M, which I think is the "last or latest so far"...and yes the N3H1-15-350M fits ALL Series RX-8's of ANY Year..

So yes, Jon, I can not understand how guys are seeing a dash light when they disconnect the wiring plug to their coolant bottle?...

Perhaps there is a possibility that Mazda changed the PCM (ECU) way of reading the voltage or NC/NO???, it is a nightmare to try and work this one out as by part number there are SO many ECU Assemblies which depend on the cars VIN Number...I could study it to try and see if the "Bottle Changes" by part number and Vehicle VIN corresponds to any changes to the PCM assy's VIN...

...Frankly can't be bothered at the monemt...:cool:

Funny story (or one that made me chuckle)....
Couple days ago at work I was working on a water chiller used for radiators in our reflow ovens.
The display kept flashing "Add Water", but the water level was fine.
I drained the tank and removed the float switch and found "gunk" preventing the float from traveling.
First thing I thought about was this thread and I looked at the display and saw the "Add Water" light was not illuminated anymore.
So that got me thinking again about this discussion... always thinking about the 8 ;)

Anyway... sorry for the side story. Back to the thread.

Coincidence? I think not!

Yeah, I think "M" is the latest and that's what I have. I still want to have someone say for sure that when they disconnect that they get a light. I can see where I(and maybe others?) read too much into threads about the coolant bottles? It's either that or they did change the way it's done and PCM as you've pointed out. I'm still not convinced.

Okay, now for my funny....errrrr........sad story! At least it has a happy ending and a little more data! :yumyum:

So last night as I was finishing up my little experiment with the old sensor and magnet, I drop the freakin magnet into the engine bay! :wallbash::wallbash:

Couldn't find the SOB anywhere...........not underneath the car, not in the lower tray, no nook and cranny....so after about an hour, I just made sure the fans would turn by hand and that it wasn't jamming up one of those and called it quits.

Well, it pissed me off all night so this morning I look again, and still no luck.
At this point I just say screw it and remove the battery and the tray to have a better look. Of course I find it hidden down beside one of the fan shrouds, so I feel alot better about that! :ylsuper:

So while I'm dicking around and putting it back together, I decide to go ahead and do one last experiment.

Everything is plugged in and normal with the "good" sensor/bottle.

I start the car and verify no coolant light. :icon_tup:

Walk around and unplug the coolant sensor connector, walk back and verify no coolant light. :icon_tup:

Here's where it gets different. Note: the car was still running(that's the only way there is any voltage to the sensor).

I had previously stripped back the wire insulation a little bit on my old sensor on the non-ground side wire, so I then hooked my meter between there and ground.

I plugged the "old" sensor in(the magnet was in my hand) and read 14.2v to ground, walked around and there was no coolant light on the dash. :icon_tup:

I then slid the magnet onto the shaft and down to where it would rest(if low coolant) and the meter went to just about 0v. Walked around to look..............and of course had a low coolant light. :icon_tup:

Just for grins I slid the magnet off and on several times while looking at the voltage on the meter and the dash light going off and on. Even if you look at the electrical schematic, you can see that one side of the reed switch is ground, so all it does is pull 4T of the PCM low, and the PCM turns on the low coolant warning light. :icon_tup: It's probably a simple resistor divider network inside the PCM.

Again, not sure if they changed the design, but in order for people to have a low coolant light with connector unplugged, they somehow have to have a short between the violet/white wire and ground..................or, there are different versions of this setup running around. :scratchhe


https://www.rx8club.com/attachment.p...9&d=1253377343

https://www.rx8club.com/attachment.p...0&d=1253377343

^................notice this bend as has been pointed out before. This could very well be some of the issue in that when you run low on coolant, especially when redlining and it draws more from the bottle, you could be heating it up enough to induce this bend(like me). And crud build-up certainly won't help either. I think the key is of course is to change coolant probably once every two years at minimum, flush bottle of all the crud(probably have to take it out to reall accomplish, and of course keep coolant close to the full line.

Think it's mainly crud build-up that takes ours out Jon. I can also see it being some heat related issues as the shaft bends and restricts magnet movement, but I think crud is the main issue.

Reflow of what? Just curious. :cool:

Wow. Giant thread.

Just unplug it. Problem solved.

If you aren't the type that likes to check their fluids ever (and, therefore, need the sensor), just take the bottle out, plug the holes, fill it with white vinegar, let it sit over night, drain it, blast it with compressed air and put it back in.
Once again - problem solved.


BTW - I use the coolant light/circuit in my car for the low bottle output on my water/meth. Its a little more important than the low coolant light.

Yeah, I know Jeff.
It was much longer than it needed to be. :sad:
And....I won't even go into the fact of the "minimal importance level" in the grand scheme. Guess I was bored!

The confusion factor is still how some reported the light on with the sensor unplugged. That doesn't make sense. :mchase:

[QUOTE=Mazurfer;3342233]Yeah, I know Jeff.
It was much longer than it needed to be. :sad:
And....I won't even go into the fact of the "minimal importance level" in the grand scheme. Guess I was bored!


No no no! I applaud your efforts! I just wanted to point out for those that are less concerned with the science and more with the result that fixing the sensor is pretty easy and requires no disassembly.

Yeah - that's not possible. An open condition is the normal state for the circuit.

I would think something like Lime-Away or C.L.R. would clean up the inside of the bottle in a jiffy. Then rinse several times thoroughly with clear water. Worth a shot if it's acting up.

I'm still a little confused about the final answer. If you want the light off, is the answer:

A. Unplug the connector, and stash the loose wire somewhere out of harm's way?

or

B. Unplug the connector and short the connector on the wire before stashing it?

One other question... Do many cars these days have a sensor and warning light for coolant level? Until I got my 8, the technology was to look at the bottle every now and then. Before that, the technology was to take the radiator cap off and look in the hole.

Ken

"A" until proven otherwise.

Yeah....the old school way was to just check the level in the radiator. Kinda like checking your tire pressure with a gauge...........ya know? :evil_laug