I have a 08 G35 base. The car sat for a year and finally got it up and running. But the cooling fans won't turn on. I noticed the wires were cut. So I bought new, installed it, still not functioning. I also noticed the a/c doesn't turn them on either. Noticed the A/C clutch doesn't engage when turned on. Checked the fuses and relays, all is in good condition. The fans spin when placed in diagnostic mode. Any ideas?

 

No refridgerant in the system? Gotta get a set of gauges or just get a recharge can at the auto store and try to add some. Does the clutch engage in diag mode?

 

The A/C evaporator was replaced. A/C system should be ok. Not sure if the clutch is engaging during diagnosic mode. I do hear clicks but, will verify later. Also, fans do not turn on when the car is at optimal temperature.

 

You should get whoever replaced the evaporator to tell you why the new ac system isn't working. Or was that you? That must be a big job....

 

It was a A/C shop that changed it out. It was working before it went down. But, no refrigerant doesn't explain why the cooling fans don't turn on when engine temperature is optimal.

 

Check this thread. Might be helpful:

https://g35driver.com/forums/general...-location.html

 

If the IPDM can drive the fans in diag mode, it should be able to drive them whenever the AC turns on (IF the ac is able to turn on) and when the coolant temp is above a certain threshold. If the IPDM can engage the compressor clutch in diag mode, it should be able to do it when the AC is turned on. That's what the diag mode is for. To confirm all the parts are able to be driven by the IPDM when their respective controls command the IPDM to do so. If the IPDM is not driving them when you turn the AC on, it's because the AC control isn't working likely because something is locking it out. The low pressure switch is the most common thing that will keep ac system from running because there's no refrigerant in the system. The car had ac work done recently presumably because of a previous problem. Any time a system doesn't work after recently being serviced, I would automatically assume that system still has a problem rather than assuming that system must be good because it had work done on it. I would assume it has a problem and would check the most common source of ac won't turn on (low pressure). It's the same with won't crank. First thing I check is battery voltage. It makes sense to check the refrigerant charge just like you would battery charge. But that's just how I debug stuff. I don't assume the battery is charged just because I know I charged it some time in the past. Does the AC button light up like the hvac controls have power and it recognizes you've pushed the button? That should happen even if the pressure switch isn't satisfied and the compressor doesn't kick on.

I'm not sure what exactly you mean by optimal temperature where you're expecting your fans to run. "Optimal" isn't a number we can compare to a spec. I don't know what the number is for engine coolant temp when the fans should cycle on and off but it's got to be something like on at 210 off at 205 or something like this. If you idle the car in the driveway eventually the fans are going to run or the car will overheat. If you monitor ECT via obd, you should see temp stabilize as the fans turn on to cool the car or it's going to overheat. If the engine temp gets to 230 and the fans don't come on even though they are able to run during diag mode, I don't know what to think. Shouldn't be possible.

 

does the car start overheadting? (the needle going past the middle) if not, how do you know that you're at the "optimal" temp for them to kick on? did you verify with a bluetooth reader/diag app? like the guy above me had said, if the fans kick on in the diag mode, then there shouldn't be anything stopping them from coming on when ecu commands them to.

does your a/c actually work? if the pressure is too low, it won't kick the compressor/fans on.