Maximum

iTrader: (5)

It appears that the A/C relay driver pin (1L) on my PFC has failed. When I turn on the A/C, the idle speed increases but the 1L pin remains at ~4.64 V. If I ground the harness side of 1L directly my compressor clutch engages as it should. Has anybody seen this before? And this is not related to the relay mod, I have that and the datalogit indicates that the PFC knows the A/C should be on. Thanks,
Max

arghx

iTrader: (3)

so you're saying that the A/C indicator comes on in the PFC etc-->sensor/sw check but 1L does not output ground? Is pin 1E (input to the ECU from the blower switch) behaving correctly?

Maximum

iTrader: (5)

Yes and yes. I even tried grounding pin 1E directly, same exact behavior.

arghx

iTrader: (3)

I can't think of anything else but a physical failure of the PFC. They don't crap out on people that much but I guess you are one of the unlucky ones. Call Apex'i and send it to them if you want to keep full A/C control behavior. Otherwise you can partially bypass the ECU by tapping the signal that goes into pin 1E and send it out to the pin 1L wire. That way you'll get your idle up and you'll get your A/C running, but you won't have the A/C compressor automatically cutting off if the engine revs high enough.

Maximum

iTrader: (5)

Yeah I doubt Apexi would do anything about it, at least not within a timeframe I'm interested in. I'll open it up and see if there are any obviously failed components. I'm also going to try swapping in a stock ecu just to make sure the PFC is not functioning properly.

Maximum

iTrader: (5)

To update, I found that my stock ECU switches the compressor on just fine so I must have some kind of failure in the PFC. I'm currently poking around trying to find what might have crapped out.

Maximum

iTrader: (5)

Since I hate it when people don't update with the solution to their problems, I'll follow this up -

I found that pin 1L is connected to the collector of one element of a NEC darlington transistor array inside the PFC. I checked to see that the base of the transistor pair was being flipped when I turned the A/C switch on but the collector was not grounding. Obviously it was faulty so I soldered in an N-channel FET over the appropriate terminals. The compressor turns on fine now.

arghx

iTrader: (3)

I'm glad you had the knowledge and skill to troubleshoot and solve the problem. I don't have that same level of experience with circuit boards.

echoi22

I have the exactly same problem with you! I'll try this fix this week.