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AC Intermittently Working (Clutch not engaging)

41K views 12 replies 4 participants last post by  NissanNut 
#1 ·
I have been dealing with a strange A/C issue the past couple of weeks, and $1k later it still isn't fixed! Has anyone else seen this?

1. The pressure in the system is correct, there are no leaks.

2. The pressure sensor has been replaced by a part obtained from the dealer.

3. The IPDM has been upgraded to the new one (apparently the clutch relay is part of the IPDM itself, it doesn't have a replaceable relay, you have to replace the whole assembly). All fuses in the engine compartment and inside the cabin are good.

4. If you run power straight to the clutch the A/C runs cold all day long.

5. The computer is not throwing any codes. The HVAC diagnostic passes with no codes (the one where you put the ignition to on and hold pause).

6. The A/C works sometimes, then other times it just stops blowing cold. When this happens the clutch is not engaged. Sometimes restarting the car gets it to kick back on, or even letting it sit a while. Resetting the computer will also let it come back on. At some point it always shuts itself off and may/may not come back on until it feels like it. It seems like it usually doesn't want to work when its real hot outside (over 105), but this is just an observation that could be all by chance.

7. The blower always runs, it's just the air isn't cold at times (when the clutch isn't engaged obviously). The A/C shows that it is on even when the clutch isn't engaged (so I believe the car thinks it has the A/C on still?)

8. If it is working (clutch engaged) and you turn the A/C off, then try to turn it back on, it usually won't come on again...

Does anyone know any other parts/issues that would cause this behavior?
 
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#3 ·
There are a number of things that could be the cause of the clutch turning off; the front air control, the BCM, the ECM or the IPDM. Since you wired up the clutch directly we know the clutch is OK.
High temp and/or pressure (over 398 PSI) will turn off the clutch, as well as throttle position. Low pressure, below 17 PSI will disengage the clutch.

When the A/C switch is pressed, or the mode switch is turned to the defroster position, the front air control outputs a compressor ON signal to BCM. The BCM then sends a compressor ON signal to the ECM, via CAN communication line.The ECM judges whether compressor can be turned ON, based on each sensor status (refrigerant pressure sensor
signal, throttle angle sensor, etc.). If it judges compressor can be turned ON, it sends compressor ON signal to IPDM E/R, via CAN communication line.
Upon receipt of compressor ON signal from ECM, IPDM E/R turns air conditioner relay ON to operate compressor.
 
#4 ·
Kind of what I feared, a bunch of sensors that the computer uses to determine if the clutch can be engaged or not... Basically only a Nissan mechanic would be able to tell what the problem is. A normal run of the mill auto guy won't have a clue.

I checked my front evaporator tonight, it is clean as a whistle. I cleaned it anyway just incase (I did run for like a year without a cabin filter at one point, so figured I should hit it with the cleaning foam anyway...) My theory was it got dirty from not having the cabin filter and was freezing up. Don't think that's the case after seeing how clean it was.

Another theory is the thermometer on the other side of the evap is failing. But that part is like $70. I'm tired of replacing parts guessing at it...

So it sounds like the other solution could be the control head, which I priced at the dealer for a cool $500. Obviously another part not worth guessing at.

Anyone have any other ideas before I take this thing to the dealer and they suggest replacing a bunch of parts that work perfectly fine? (yeah, I'm skeptical)
 
#6 ·
Definately something going on with A/C due to heat. WOrks fine when its less than 105* outside. Over 105 (like today it was 113-115*) and it wouldn't come on.

I have found that switching it on/off and between defrost does help it come on sometimes.

Anyone got any ideas why the clutch won't engage when it's hot outside?
 
#7 ·
Any new information about this problem (or solutions from other forum members)? I'm experiencing the same issue with my 2004 Armada. The exact same issue. Any resolution to this problem would be greatly appreciated. The Armada environmental system is overly complex, so stabbing in the dark is going to be $$$$. Thanks!
 
#11 ·
Could be related. There is a chart in FSM thats shows what the resistance should be for a given temp. The odd thing is the FSM calls this sensor an Intake sensor. Courtesy calls it the sun load sensor.

I updated my webpage with better info.

Here is the part number. You can test yours today with an ohmmeter.

 
#12 ·
NissanNut, I ordered the sunload sensor for the Armada and the part looks very different from yours. I'll see if I can upload a photo of it when I get home. What is the Nissan OEM part number?
 
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