Annyoing A/C on in most modes fix
01-17-2006, 01:28 PM
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Annyoing A/C on in most modes fix
If you're like me, you're annoyed that the A/C is on in all modes except "dash only." I'm even annoyed that the A/C can't be overridden in defrost only mode, since once you defrost a windshield, a bit of warm air usually keeps it unfogged. Personally, I like the A/C only on when the A/C button is manually pushed.
I have a plan to fix this that I'm halfway through implementing.
Here's the deal: The A/C button "works" all the time, in that you can push the A/C button and the green light will toggle. In dash mode this actually controls the A/C. In other modes, this just turns on a green light and makes you mad that the A/C is running when it's 42 degrees out.
If only the A/C button could actually control the A/C clutch! Well, it can. Over the weekend I did a PhatNoise MP3 player install in the 8, and while I had the radio out, I soldered two wires on the A/C LED. It turns out it's really easy to get to, since the PC board sticks up a bit from the A/C controls, and the only thing really exposed is the A/C LED terminals.
Now I have two wires in the car that have 0V across them when the LED is off and about 2V across them when the LED is on. I plan on running this to a transistor, using in to interrupt the current at the A/C clutch relay (under the hood). Thus, when the LED is on, the A/C system can control the A/C clutch. When the LED is off, the clutch cannot be activated. Volia! Manual control of the A/C system in the car, in all modes.
I'll finish the install this weekend and let you know how it goes, as well as taking a few pics. If it works, you should be able to solder one wire on the back of the A/C controls, run this wire under the hood into a transistor through a resistor, and put the transistor in-line with a wire. A pretty basic DIY.
For now, I'd like to know if anyone sees any problems with this. Am I missing any logic that the A/C system has or am I going to throw a CEL?
I have a plan to fix this that I'm halfway through implementing.
Here's the deal: The A/C button "works" all the time, in that you can push the A/C button and the green light will toggle. In dash mode this actually controls the A/C. In other modes, this just turns on a green light and makes you mad that the A/C is running when it's 42 degrees out.
If only the A/C button could actually control the A/C clutch! Well, it can. Over the weekend I did a PhatNoise MP3 player install in the 8, and while I had the radio out, I soldered two wires on the A/C LED. It turns out it's really easy to get to, since the PC board sticks up a bit from the A/C controls, and the only thing really exposed is the A/C LED terminals.
Now I have two wires in the car that have 0V across them when the LED is off and about 2V across them when the LED is on. I plan on running this to a transistor, using in to interrupt the current at the A/C clutch relay (under the hood). Thus, when the LED is on, the A/C system can control the A/C clutch. When the LED is off, the clutch cannot be activated. Volia! Manual control of the A/C system in the car, in all modes.
I'll finish the install this weekend and let you know how it goes, as well as taking a few pics. If it works, you should be able to solder one wire on the back of the A/C controls, run this wire under the hood into a transistor through a resistor, and put the transistor in-line with a wire. A pretty basic DIY.
For now, I'd like to know if anyone sees any problems with this. Am I missing any logic that the A/C system has or am I going to throw a CEL?
Last edited by dsmdriver; 01-17-2006 at 01:33 PM.
01-17-2006, 01:28 PM
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Ok, I finally got this finished over the weekend and it works great.
Here's the quick description. I'll try and add pictures and a schematic later.
Materials needed:
About 10 feet of 20ga or lower wire
About 1 foot of 16ga or lower wire
(4) spade terminals
(4) blade terminals
(1) 2.2Kohm resistor (RS # 271-1121)
(1) 2907 transistor (RS # 276-2023)
1) Take your radio out of the dash.
2) Take the radio out of the whole dash mount thing
You can do #1 and #2 using the instructions from here:
http://www.whatsmyip.org/ipodrx8/
Go up to the last step on page 8.
3) Take the support bracket off of the control panel. Four screws in the corners.
4) Now solder a wire onto the control panel. There are a few solder pads exposed in the lower center of the control panel. Two of them are right behind the A/C LED. You want to solder to the left LED (as referenced from looking at the back of the control panel). I suggest a 2' wire on here, but if you want to try and get a wire long enough to pull all the way to the engine at this time, be my guest.
See the picture for where to attach this wire.
5) Put the radio back together and put it back in the car, making sure the wire is accessible and not shorting on anything. Leave the wire hanging out into the driver's footwell (LHD cars).
5.5) With the key in the on position and the engine off, check the operation of this wire. Make sure your fan is on at least level "1" or the A/C light won't toggle.
Put a voltmeter between this wire and +12V in the car. The cig. lighter is an easy, close place to get +12V with a voltmeter probe. When the A/C light is lit, your voltmeter should read about 12V. With the A/C light off, it should read near 0V. This wire is grounding itself when the A/C light is on and an open circuit when its off.
If you get weird voltages like 2.3V or 9V, you hooked to the wrong leg of the LED.
6) Under the hood, open the fusebox (driver's side on LHD cars)
7) Pull the A/C relay. It's labeled on the top of the box, and is near the front of the car. This should have four "legs" on it, two silver and two copper colored.
What we need to do is extend all of these wires. One of them will be extended with a transistor in-line, the rest will just be exensions.
8) Make up two 4" exensions using blue spade/blade terminals. Use at least 16ga wire here. These connect to the copper terminals. on the relay and plug into the related spot in the fusebox.
9) Make up two 4" extensions using red spade/blade terminals. The blades that go into the fusebox will need to be trimmed down in width to fit in here if you have the same width ones I did. You can use 20ga or lower wire here.
10) Cut one of the extensions about 1" back from the spade terminal (the one that hooks to the relay).
11) Hook the blade side of the wire to the transistor's collector. If you put the flat side of the transistor down with the leads towards you, this is the lead on the left.
12) Hook the spade side of the wire to the emitter. This is the lead on the right.
13) Hook the wire that you want to go into the car into the base, the middle lead. You can do this step later if you want to pull the wire first.
14) Re-hook up the relay using your 4 extensions. The two copper terminals hook straight through. The un-cut wire goes on the silver terminal that is closest to the engine / center of the car. The cut one with the transistor in-line goes closest to the fender.
15) Hook the 2.2Kohm resistor to the wire that is in the car. Hook another wire to the other side of the resistor. Run this wire through the firewall and hook it to the center lead on the transistor.
16) Insulate all of the wires, put the cover back on the fuse box, and you're done!
Your A/C will now only operate when the A/C light is lit. This means that to get good defrost, you need to press the defrost button and then the A/C button. It also means that once the window is defogged, you can turn the A/C off and leave the heat on the window.
This also means the A/C will need to be run manually every once in a while to keep the seals in the A/C unit lubricated.
This works by interrupting the signal from the ignition switch to the A/C clutch relay. The ECU still has control over the A/C, so it will still cycle, turn off at WOT, etc. But it cannot turn ON unless the A/C light is lit, since the other side of the relay only has power when the transistor is on.
Notes:
2.2Kohm resistor could be anything from 1000 ohms to 10Kohms. Doesn't really matter, it's just here for protection of the A/C controls if anything shorts.
The 2907 transistor could be any generic NPN transistor, like a 2N3906 or 2N2222. The relay uses 125 mA of current, so just make sure it can handle this.
Here's the quick description. I'll try and add pictures and a schematic later.
Materials needed:
About 10 feet of 20ga or lower wire
About 1 foot of 16ga or lower wire
(4) spade terminals
(4) blade terminals
(1) 2.2Kohm resistor (RS # 271-1121)
(1) 2907 transistor (RS # 276-2023)
1) Take your radio out of the dash.
2) Take the radio out of the whole dash mount thing
You can do #1 and #2 using the instructions from here:
http://www.whatsmyip.org/ipodrx8/
Go up to the last step on page 8.
3) Take the support bracket off of the control panel. Four screws in the corners.
4) Now solder a wire onto the control panel. There are a few solder pads exposed in the lower center of the control panel. Two of them are right behind the A/C LED. You want to solder to the left LED (as referenced from looking at the back of the control panel). I suggest a 2' wire on here, but if you want to try and get a wire long enough to pull all the way to the engine at this time, be my guest.
See the picture for where to attach this wire.
5) Put the radio back together and put it back in the car, making sure the wire is accessible and not shorting on anything. Leave the wire hanging out into the driver's footwell (LHD cars).
5.5) With the key in the on position and the engine off, check the operation of this wire. Make sure your fan is on at least level "1" or the A/C light won't toggle.
Put a voltmeter between this wire and +12V in the car. The cig. lighter is an easy, close place to get +12V with a voltmeter probe. When the A/C light is lit, your voltmeter should read about 12V. With the A/C light off, it should read near 0V. This wire is grounding itself when the A/C light is on and an open circuit when its off.
If you get weird voltages like 2.3V or 9V, you hooked to the wrong leg of the LED.
6) Under the hood, open the fusebox (driver's side on LHD cars)
7) Pull the A/C relay. It's labeled on the top of the box, and is near the front of the car. This should have four "legs" on it, two silver and two copper colored.
What we need to do is extend all of these wires. One of them will be extended with a transistor in-line, the rest will just be exensions.
8) Make up two 4" exensions using blue spade/blade terminals. Use at least 16ga wire here. These connect to the copper terminals. on the relay and plug into the related spot in the fusebox.
9) Make up two 4" extensions using red spade/blade terminals. The blades that go into the fusebox will need to be trimmed down in width to fit in here if you have the same width ones I did. You can use 20ga or lower wire here.
10) Cut one of the extensions about 1" back from the spade terminal (the one that hooks to the relay).
11) Hook the blade side of the wire to the transistor's collector. If you put the flat side of the transistor down with the leads towards you, this is the lead on the left.
12) Hook the spade side of the wire to the emitter. This is the lead on the right.
13) Hook the wire that you want to go into the car into the base, the middle lead. You can do this step later if you want to pull the wire first.
14) Re-hook up the relay using your 4 extensions. The two copper terminals hook straight through. The un-cut wire goes on the silver terminal that is closest to the engine / center of the car. The cut one with the transistor in-line goes closest to the fender.
15) Hook the 2.2Kohm resistor to the wire that is in the car. Hook another wire to the other side of the resistor. Run this wire through the firewall and hook it to the center lead on the transistor.
16) Insulate all of the wires, put the cover back on the fuse box, and you're done!
Your A/C will now only operate when the A/C light is lit. This means that to get good defrost, you need to press the defrost button and then the A/C button. It also means that once the window is defogged, you can turn the A/C off and leave the heat on the window.
This also means the A/C will need to be run manually every once in a while to keep the seals in the A/C unit lubricated.
This works by interrupting the signal from the ignition switch to the A/C clutch relay. The ECU still has control over the A/C, so it will still cycle, turn off at WOT, etc. But it cannot turn ON unless the A/C light is lit, since the other side of the relay only has power when the transistor is on.
Notes:
2.2Kohm resistor could be anything from 1000 ohms to 10Kohms. Doesn't really matter, it's just here for protection of the A/C controls if anything shorts.
The 2907 transistor could be any generic NPN transistor, like a 2N3906 or 2N2222. The relay uses 125 mA of current, so just make sure it can handle this.
Last edited by dsmdriver; 01-30-2006 at 04:22 PM.
01-17-2006, 01:59 PM
#5
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Originally Posted by dsmdriver
makes you mad that the A/C is running when it's 42 degrees out.
01-17-2006, 02:52 PM
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Originally Posted by zoom44
this leads me to think that you believe that Air Conditioning only means cooling or cold air. Is it your belief that AC on means cold air blowing?
It's my understanding that the A/C compressor always runs in all modes except "dash only."
Yes, you can crank up the heat and then pass hot air past the air conditioner, leading to slightly less warm air. Always struck me as weird to run an A/C compressor that takes power from the engine and then use the waste heat from that engine to warm the same air. Not exactly an efficent system, although it does lead to dry air.
01-17-2006, 04:44 PM
#7
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so the answer is yes then- you think AC means cold air.
Air Conditioning means just that- conditioning the air. One aspect of that is cooling the air. but it is only one aspect. the other is dehumidifying. It doesnt do any cooling unless you hae selected a cold setting from the temp control.
the air you exhale is full of moisture which condenses on the windshield along with the normal moisture in the air. by keeping the selection to ouside air and using the AC when defrost is selected to dehumidify the air the winshield is cleared much faster/easier.
All cars do this- most Japanese brands you can "select" the AC and have for a long time but most today actually have it selected automatically anyway. The US Domestic brands have been turning it on automatically for along time- Ford since the 60s.
Mazda does as well. With the RX-8 they have also chosen to run the defrost whenever floor is selected. Do you think that was an arbitrary decision? It was not. Because of the placement of the heating unit , the condenser, the run of the ducts, the seating position and the windshield, the windshield has a tendency to fog over when floor is on if defrost/fog is not selected. to deal with this Mazda designed the system to use the defrost (and hence AC) when floor was selected.
Most cars actually have defrost selected when floor is selected now.
Several things to note- the AC compressor doesnt work above 65% throttle. Also it does not operate below 36 degrees f outside temp- as it wouldnt do anything but freeze the condensor then.
Air Conditioning means just that- conditioning the air. One aspect of that is cooling the air. but it is only one aspect. the other is dehumidifying. It doesnt do any cooling unless you hae selected a cold setting from the temp control.
the air you exhale is full of moisture which condenses on the windshield along with the normal moisture in the air. by keeping the selection to ouside air and using the AC when defrost is selected to dehumidify the air the winshield is cleared much faster/easier.
All cars do this- most Japanese brands you can "select" the AC and have for a long time but most today actually have it selected automatically anyway. The US Domestic brands have been turning it on automatically for along time- Ford since the 60s.
Mazda does as well. With the RX-8 they have also chosen to run the defrost whenever floor is selected. Do you think that was an arbitrary decision? It was not. Because of the placement of the heating unit , the condenser, the run of the ducts, the seating position and the windshield, the windshield has a tendency to fog over when floor is on if defrost/fog is not selected. to deal with this Mazda designed the system to use the defrost (and hence AC) when floor was selected.
Most cars actually have defrost selected when floor is selected now.
Several things to note- the AC compressor doesnt work above 65% throttle. Also it does not operate below 36 degrees f outside temp- as it wouldnt do anything but freeze the condensor then.
01-17-2006, 05:03 PM
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I'm a bit confused- how do you dehumidify air except by cooling it? A/C that I know of only has one mode of operation- make the condenser very cold. This "squeezes" the water out of the air with the low temp. If you want to have hot air after this, you then have to heat it up from a lower than ambient temp up to an above ambient temp. The A/C is always "cooling" the air, it's just that you can then also heat that air way up afterwards.
I'm well aware that A/C has a dehumidifying effect, and I by no means want to loose that. If I didn't care about that, I'd just pull the A/C fuse in the winter. However, once a window is defogged, some heat on the window will usually keep it fog free since the higher than ambient temp can accept more moisture before it will condense. Personally, I hate the idea of a 5-10HP A/C compressor running all the time when just a little heat will do.
My last car only ran the A/C when you asked for it (even in defrost mode) and my wife's previous car was modified to allow defrost without A/C as well. They both performed totally fog free if you just kept a bit of heat on the window.
Finally, I've put 1000 miles on this RX8 now, and I have yet to get more than 14 MPG, even on a 150 mile highway drive with the cruise on at 70 MPH. I'm doing everything I can to save a little gas, and not running the A/C all winter will probably help.
I'm well aware that A/C has a dehumidifying effect, and I by no means want to loose that. If I didn't care about that, I'd just pull the A/C fuse in the winter. However, once a window is defogged, some heat on the window will usually keep it fog free since the higher than ambient temp can accept more moisture before it will condense. Personally, I hate the idea of a 5-10HP A/C compressor running all the time when just a little heat will do.
My last car only ran the A/C when you asked for it (even in defrost mode) and my wife's previous car was modified to allow defrost without A/C as well. They both performed totally fog free if you just kept a bit of heat on the window.
Finally, I've put 1000 miles on this RX8 now, and I have yet to get more than 14 MPG, even on a 150 mile highway drive with the cruise on at 70 MPH. I'm doing everything I can to save a little gas, and not running the A/C all winter will probably help.
01-17-2006, 05:18 PM
#9
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3hp and even 5-10 you cant feel plus when you want to go fast it stops working. your last carwas probably pre95 or 96 which is when nearly every automaker that hadnt previously went to always on AC with defroster.
if you have gone 150 in one shot(start to end) on the highway with cc on 70mph straight to a gas station and not gotten over 20mpg you have a much larger problem then the AC. 70 and cc on nonstop on the highway will easily get you 22 and possibly 24 or better(depending on conditions)
you should get your car checked out- look for a stuck thermostat or some other reason the car would stay in open loop under that cruise conditon. the car staying in open loop is the only thing that can cause such poor highway mileage at those speeds. many of us have seen 24mpg at 80.
not running the ac during the winter is also a good way to kill the AC. not running it for long stretches can dry out the seals etc.
if you have gone 150 in one shot(start to end) on the highway with cc on 70mph straight to a gas station and not gotten over 20mpg you have a much larger problem then the AC. 70 and cc on nonstop on the highway will easily get you 22 and possibly 24 or better(depending on conditions)
you should get your car checked out- look for a stuck thermostat or some other reason the car would stay in open loop under that cruise conditon. the car staying in open loop is the only thing that can cause such poor highway mileage at those speeds. many of us have seen 24mpg at 80.
not running the ac during the winter is also a good way to kill the AC. not running it for long stretches can dry out the seals etc.
01-17-2006, 05:37 PM
#11
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7
No cool air
DESCRIPTION
*
Magnetic clutch does not operate.
POSSIBLE CAUSE
*
Malfunction in PCM A/C cut control system (Step 3)
*
Malfunction in A/C amplifier (Step 4)
*
Malfunction in refrigerant pressure switch (Steps 5, 7—9)
*
Malfunction in PCM (A/C signal) (Step 6)
*
Malfunction in PCM (IG1 signal) (Steps 10, 11)
*
Malfunction in A/C compressor (Step 12)
*
Malfunction in A/C relay (Steps 13—15)
*
Malfunction in evaporator temperature sensor (Step 16)
No cool air
DESCRIPTION
*
Magnetic clutch does not operate.
POSSIBLE CAUSE
*
Malfunction in PCM A/C cut control system (Step 3)
*
Malfunction in A/C amplifier (Step 4)
*
Malfunction in refrigerant pressure switch (Steps 5, 7—9)
*
Malfunction in PCM (A/C signal) (Step 6)
*
Malfunction in PCM (IG1 signal) (Steps 10, 11)
*
Malfunction in A/C compressor (Step 12)
*
Malfunction in A/C relay (Steps 13—15)
*
Malfunction in evaporator temperature sensor (Step 16)
01-17-2006, 05:39 PM
#12
Administrator
INSPECT FOR DTC IN PCM
*
Inspect for DTCs related to the PCM on-board diagnostic system.
*
Are any DTCs displayed?
INSPECT TO SEE WHETHER MALFUNCTION IS IN A/C AMPLIFIER OR ELSEWHERE
*
Does cool air blow out when terminal 1M of A/C amplifier connector (24-pin, A/C signal) is grounded?
*
Inspect for DTCs related to the PCM on-board diagnostic system.
*
Are any DTCs displayed?
INSPECT TO SEE WHETHER MALFUNCTION IS IN A/C AMPLIFIER OR ELSEWHERE
*
Does cool air blow out when terminal 1M of A/C amplifier connector (24-pin, A/C signal) is grounded?
01-17-2006, 06:08 PM
#13
Metatron
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Logic.....
I like the concept.
I pulled the fuse last spring and ran for many thousand miles, I'm fairly sure it throws no codes, it still thinks it's "in control".
I would only add one more gate to your logic, along the lines of Zoom's concerns - have the relay cut the clutch ONLY when the light is off AND the "outside air" LED is lit. This would still dehumidify if you chose to recycle the internal air, but give you the cut-off if using fresh air.
If you make up little transistor/relay boards, please put me down as your first order!
S
I pulled the fuse last spring and ran for many thousand miles, I'm fairly sure it throws no codes, it still thinks it's "in control".
I would only add one more gate to your logic, along the lines of Zoom's concerns - have the relay cut the clutch ONLY when the light is off AND the "outside air" LED is lit. This would still dehumidify if you chose to recycle the internal air, but give you the cut-off if using fresh air.
If you make up little transistor/relay boards, please put me down as your first order!
S
01-17-2006, 08:30 PM
#14
Administrator
what if you had a like aswitch and resistor on the temp sensor wire then you could just switch it and adjust the voltage so the ac amp/pc would see its below the 30 something degree f limit and not allow it to come on?
the electronics is not my game so that could be a lame idea. i dont know. ill have to dig into the manuals more tomorrow.
the electronics is not my game so that could be a lame idea. i dont know. ill have to dig into the manuals more tomorrow.
01-18-2006, 11:12 AM
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The AC compressor runs to dehumidify the air on defrosting.
Removing the humidity/water from the air is part of the function of defrosting.
Its not all about the temperature of the air, but also the amount of water in it.
Removing the humidity/water from the air is part of the function of defrosting.
Its not all about the temperature of the air, but also the amount of water in it.
01-18-2006, 12:17 PM
#16
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Simply heating outside air lowers its relative humidity. Yes, the AC can help lower it further but is by no means necessary at all times. I spent 20 years previous to the RX-8 driving cars with no AC whatsoever in various climates, so I am fairly confident one can survive.
Being of sound mind and body (ok, at least mind...), I can easily tell when the windshield is beginning to fog and I'm fully capable of pressing a button to activate AC to enhance the anti-fogging. I'd just like the option of turning it off when no longer necessary. The other point about keeping the seals healthy is a good one. Don't forget to exercise the AC regularly if you implement this change. It might even be a good idea to design the circuit to keep power to the AC clutch available for the first few minutes of starting regardless of switch setting, but that is a minor nit.
Cheers for this mod!
Being of sound mind and body (ok, at least mind...), I can easily tell when the windshield is beginning to fog and I'm fully capable of pressing a button to activate AC to enhance the anti-fogging. I'd just like the option of turning it off when no longer necessary. The other point about keeping the seals healthy is a good one. Don't forget to exercise the AC regularly if you implement this change. It might even be a good idea to design the circuit to keep power to the AC clutch available for the first few minutes of starting regardless of switch setting, but that is a minor nit.
Cheers for this mod!
01-18-2006, 12:27 PM
#17
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Love the idea, let me know how it works. Cycling the AC to keep the seals happy is easy enough, and being able to turn it off would make me happy. I hate running the AC when it doesn't need to run, and not being able to turn it off drives me nuts.
01-18-2006, 12:31 PM
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Originally Posted by Imidazole
Its not all about the temperature of the air, but also the amount of water in it.
The A/C removes the water from the air by cooling it below the dew point, causing the water to condense out of the air. The air is then heated back up, which means the relative humidity is much lower. As I said before, I am well aware that the A/C dehumidifies the air. I'm also well aware that it does this by cooling the air off. I'm also totally sure that air heated from 40 degrees to 75 degrees has a much, much lower relative humidity than it did at 40 degrees (even without being cooled first) and thus the 75 degree air can do a good job of defogging all on it's own, without the inefficency of being cooled first.
01-18-2006, 12:37 PM
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Okay- I have an idea for auto-cycling of the seals. What if I make the mod such that it runs the A/C compressor while the engine is cranking? I've seen in various tech manuals that this is common nowadays, and would be really easy to implement.
Right now, the design is really, really simple. It isn't a PC board or anything "smart." It's literally a wire and a $1.29 transistor from radio shack. Adding a timer or anything that will auto cycle the A/C for you is a huge increase in complexity. However, having it click the A/C on for you during the cranking would be easy with a single diode. Heck, for all I know, the RX8 already does this, and I just need to allow it.
Right now, the design is really, really simple. It isn't a PC board or anything "smart." It's literally a wire and a $1.29 transistor from radio shack. Adding a timer or anything that will auto cycle the A/C for you is a huge increase in complexity. However, having it click the A/C on for you during the cranking would be easy with a single diode. Heck, for all I know, the RX8 already does this, and I just need to allow it.
01-18-2006, 01:46 PM
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I checked the A/C cycling on my CanScan unit. The A/C does cycle in anything but dash only, but the cycle time isn't enough to worry about. I will try to get some numbers tonight but it looked like less than 1 second of cycling about every 15 seconds. This is not a significant loss due to the short impulse.
01-18-2006, 02:00 PM
#21
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Did it cycle much longer in "A/C on" mode with the green A/C light lit? 1/15th duty cycle may just be what the A/C can run when it's cold outside (I see that it's low 40's in GA right now).
I can tell when I click on the defrost that I have to turn up the heat in the car since the A/C cools it off a fair amount. I was assuming by this that the A/C was running quite a bit.
I can tell when I click on the defrost that I have to turn up the heat in the car since the A/C cools it off a fair amount. I was assuming by this that the A/C was running quite a bit.
01-18-2006, 02:06 PM
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Was a continuous cycle with the A/C on button depressed, but I didn't give it long enough to go through a full cycle. Like I said I'll run it tonight and make a graph so everyone can see. The A/C should run the same on defrost as it does if the button is depressed.
01-18-2006, 05:27 PM
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I will attach the graphs later (don't want to hassle with getting them off the laptop at the moment) but here are some results:
Ambient: 45 degrees F
Engine speed: idle
Computer mode: closed loop
A/C On, dash setting - A/C on time 3 seconds, Frequency 30 seconds
A/C off, defrost on - A/C on time 3.5 seconds, Frequency 30 seconds
A/C off, floor - A/C on time 3.5 seconds, Frequency 30 seconds
Same cycle frequency on each, but it is different than what I had last night. The USA spec system has an ambient air temperature sensor in addition to the refrigerant pressure switch. This would account for the previously stated idea that the A/C does not operate below 36 degrees F. Either way, it doesn't seem you're losing much from the A/C coming on in other modes.
Ambient: 45 degrees F
Engine speed: idle
Computer mode: closed loop
A/C On, dash setting - A/C on time 3 seconds, Frequency 30 seconds
A/C off, defrost on - A/C on time 3.5 seconds, Frequency 30 seconds
A/C off, floor - A/C on time 3.5 seconds, Frequency 30 seconds
Same cycle frequency on each, but it is different than what I had last night. The USA spec system has an ambient air temperature sensor in addition to the refrigerant pressure switch. This would account for the previously stated idea that the A/C does not operate below 36 degrees F. Either way, it doesn't seem you're losing much from the A/C coming on in other modes.
01-18-2006, 11:02 PM
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Originally Posted by dsmdriver
I can tell when I click on the defrost that I have to turn up the heat in the car since the A/C cools it off a fair amount. I was assuming by this that the A/C was running quite a bit.