right, i have a scangauge that shows my water temp.. you mention checking relays to try out both fans.. but after i remove the intake box I wont be able to visibly see both?

You don't need to remove the intake - just listen for when they turn on .
The reason you need to pull the relay for the first fan is that the engine will never get hot enough to kick in the second fan if the first one is running .
Fan one is at 98C and fan 2 is 101C (from memory) .

how about turning the A/C on?

yes that will kick in fan 1 but it does not test your temp sensor or fan 2

so how about this for a hypothesis as to why my fuse is blowing..

Fan 1 works fine.. when I reach the temp for Fan 2 to come on.. it doesn't (failed?).. so then the fuse blows because Fan 2 is probably faulty?

That would also explain why my car has been running hot these last 2 days ever since the first time the fuse went..

time to take your intake off and inspect the fan :) . Like the other guy found - if it is stiff to turn it will draw too much current and blow the fuse . Other than that it could be a wireing short ....

right, but will i have access to both fans when removing the intake assembly?

pretty sure you will - if not you may have to remove battery tray as well :(

wireing diag for reference :

i just went downstairs and tried to do some relay pulling.. i couldn't get it warm quick enough.. so I turned on the A/C and it went up to 190f.

fan was on, pulled relay 1.. nothing, pulled relay 2.. a fan went off and about 10 seconds later i do believe the other fan went on...

regardless, I never got the car warm enough to have both fans on so it's something I'll try tomorrow when I take it out for a drive.

correction : just looking at the wireing diagram I see that the first stage actually has both fans running in series (ie slow) .
The second stage kicks the fans into parallel (both running at max.)
At least that is how i read the diagram .
Sorry for the misinformation earlier ......the test i descibed still will check if your system is ok although pulling relay 1 will prevent fan 1 from running in high speed mode as well as both fans in slow speed mode.

alright, so I think my best bet now would be to take out the airbox and visually and manually inspect them.

The fan blades are different too which seems odd. The drivers side fan has wider blades but they are not symmetrical. Just seems like too complicated of a setup. I'm going to override the whole system when i get my new fans back in. I want control this time.

$195 for each fan. I can get them for $135 through a friend with his employee discount. When i put 12V to these fans they should run right??? Neither of mine do...

This is all very interesting... I had noticed since it got warmer outside and on longer trips that my fans weren't kicking on after I turned off the car. I didn't have a chance to really check into it and honestly didn't think much of it since I never had any indication that the car was overheating. I really couldn't remember the last time I had noticed the fans kick on.

Then I blew a seal. Preface... I am of the opinion that my reman was weak to begin with but I'm sure a cooling problem didn't help it.

Even though I never mentioned my concern, the dealer found that I had a blown fuse, I don't know to which fan or both or what but they suspect my engine overheated, thus blowing an apex seal. My replacement engine is on its way.

My question is, why didn't I get a temp light or coolant boil over or any other indication of overheating? My coolant level stays right on the full line when I check it cold. When hot, it is at a higher level but I assumed that was normal. I don't want this to happen again... I hope they figure out what blew the fuse in the first place.

Scary stuff. Those of you who have had boilovers should also check the power steering connector that is right underneath the coolant vent. open it up, clean it out and put it back together.

The last hot spell we had here made my fans kick on after my car was turned off. The fans were louder then my engine at idle.

Good call! I had coolant everywhere... I'm going to extend the overflow tube down past the engine bay this time. Good thinking Mazda....

Why the hell did you do it that way?!?! What a mess.
You should take it out the bottom. Its a 10-minute job that way.

The OE fans have asymmetrical blades to reduce noise. They aren't particularly high flow fans (1260 and 1600 CFM), but they are fairly low current.

I have a pair of 2200 CFM fans that were on my Koyo (didn't help). Now that I am back to the stock rad it doesn't overheat, but I'll probably try to fit the bigger fans to the OE rad and see the result.

Ok calling all electrical engineers (like myself) lets study this one a bit.

Fan Motor - Hello $150.
http://i96.photobucket.com/albums/l1...4/P1010314.jpg
Gotta take the back off.
http://i96.photobucket.com/albums/l1...4/P1010316.jpg
So far.... normal.
http://i96.photobucket.com/albums/l1...4/P1010317.jpg
One brush is ate up.... possible arcing? I found no trace of springs to keep the brushes on the armature... that doesn't mean they were not there but i didn't recover them. EDIT: I found one... stay tuned.
http://i96.photobucket.com/albums/l1...4/P1010319.jpg
Winding are smoked. Also note the damage to the surface that contacts the magnets. Its blurry i know....
http://i96.photobucket.com/albums/l1...4/P1010323.jpg
Case was full of all the melted goo from the armature. This thing got extremely hot. Front bearing was all but locked up... maybe the beginning of the problem.
http://i96.photobucket.com/albums/l1...4/P1010320.jpg

Who wants to speculate???

that kind of thing can be summed up with this scientific explanation -
Shit Happens !

Ok.... so i was SUPPOSED to pick up my new fan motor today and yep you guessed it, wrong part. Apparently Mazda cross references both motors to the drivers side style and i need the passenger side. I'm getting free shipping on the part now since they messed up but it cost me $10 in gas today and $10 more on Monday to go pick it up. Good thing i own other cars... i'll just be 8less for a few more days. I hate people :rant: . /rant

Ok, I'll have a go at this.

This is a brushed (as opposed to brushless) DC motor. The brushes are obviously fried, but probably not due to arcing, since that's what they're for. Unless of course the arc currents are too high creating heat, expanding them, increasing friction with the commutator, creating more heat, and so on. With the wire damage, most likely currents did get too high. Most likely over a long period of time, what began as short current spikes grew to longer, higher amplitude spikes, and are the root cause, ultimately resulting in fuses blowing Assuming that's true, the question is how/why the currents were high.

Theory #1. The condition of the windings is the biggest clue, along with the damage to the magnets Since DC motors must spin to produce a back EMF, which limits current of course, any problems getting the motor to start up (i.e. too much friction somewhere, bearings, magnet clearance to housing etc) would cause high currents on cycling for longer periods of time than the motor windings, and brushes, were designed for. These high currents were of short enough duration to keep the fuse from blowing (they take lots of time to blow relative to this transient). Over many cyclings, the windings began failing and shorting out, reducing the motors torque producing capability which simply exacerbated the problems created by the increase friction in the bearings or elsewhere. Then of course, the currents increased and the fuses began to blow due to increased startup currents and/or intermittent shorts in the windings.
Or...the windings started the problem with an intermittent short(s), creating higher currents and getting worse over time. Of course, and as the multiple failures indicate, all these problems feed on each other, resulting in a cascade of failures.

Theory #2. The condition of the brushes is also a clue. Looks like they've been overheated due to friction and/or high currents, both potentially creating failures that cause the other and more. If they are somehow causing shorts across the commutator, then that may be a failure mechanism. Doesn't explain the winding damage though, so I doubt it.

Theory #3. I've not seen a schematic, so I don't know if current limiters are in the motor circuit. Do these motors have any active circuits that limit current other than the fuse? If so, I'd be checking those before installing a new motor. Additionally brush arcs represent pretty high voltages and prevent "flyback" like voltages from being dropped across drive circuits. If the commutator has intermittent shorting going on, the circuits limiting current to the motor may've been subjected to these large voltages, and therefore damaging them, allowing large currents into the motor, damaging the windings and the wires from the battery.

Theory #4. The magnetic circuit in your motor is somehow weakened. This prevents the proper amplitude of induced back EMF and your windings/brushes have been subject to large currents over time, causing them to ultimately fail. I doubt it. Magnets are damn reliable, lol. And this wouldn't explain the apparent mechanical wear on the magnets.

Theory #5. The brush springs are out of spec or being impeded, creating too much pressure resulting in a short across the commutator. Doesn't explain the failed windings though so I doubt it.


I have other theories (I may write them later if I remember to do so). But almost any combination of the above would cause these apparently cascaded failures- windings fail, brushes fail, wires fail, ending in blown fuses.

Finally, I'm digital integrated circuit design engineer. It's been 16 years since I took any classes related to AC/DC motors so the above theories may be complete BS, but I don't think so.

Fan 1 may work fine, but blowing fuses indicates an intermittent problem in either fan motors or its drive circuits. Switching on of fan 2 will of course increase the current load, assuming they are in parallel (most likely), but fan1 may be at fault. There is no way of telling (definitively) without measuring the currents drawn by each fan and comparing the measurements with their specifications.

Also, the problem may not be intermittent, which would mean the current in the circuit is on the threshold of blowing all the time and some transient, in this case fan2, in other casese probably heat, is finally pushing the fuse current past its intended limit. Fan2 may be the cause, but not necessarily.

If there are no drive circuits between the fuse and the fans, then one, or both (not likely), of your fan motors is probably on its way out. Drive cicuits include anything to a simple relay to a PWM controller (you don't have a PWM controller, but you may have current limiting circuits for speed control, etc).

It could be an intermittent short in the wires leading to fan 2 but that is less likely than the fan motor(s) itself (motor assemblies have a much higher failure rate than do wires that simply carry current to their electrical loads).

Just in case you or others are tempted to put in a larger fuse, don't. My jacka$$ for a brother in law (he's a jacka$$ for reaons other than this) once replaced a fuse with an aluminum foil gum wrapper. From what I recall it ruined the entire car (many wires fried because of their proximity to the ones carrying the short circuit current). Now that foil wasn't a fuse of course, it could carry a lot more current than a fuse. But you get the idea. This would include removing the fan motors and hooking them directly to a 12v source...i.e. don't do this unless you know for a fact it's a 12v motor (it probably is) and you don't care if the now unfused motor circuit is completely fried. Doing this however might tell you that it is in fact motor #2 that's the problem.

Good read! When i applied 12V directly to the blown motor it would struggle to turn over and eventually melted one of the lead wires. Note to Mazda - THIS IS A MOTOR THAT SHOULD NOT FAIL OVER THE LIFE OF THE CAR. Try spending a little extra money to go brushless with better sealed bearings. I'm very disappointed in this design for such a critical component.

Wow. Thanks for the writeup. I guess I'll give the fans a spin when I check the oil from now on to make sure there's no binding.

Digital, ya missed one - a single grommet stuck between blade and housing would burn the motor out pronto.

Gentlemen, check your grommets!


S