420A Automatic Compressor ECU Diagnosis

[Event Horizon01]

Hello again my fellow DSMers, I recently ran into A/C problems again on my 97 GS but managed to fix it yet again. My A/C quit on me completely in the sense that the A/C button would be on green but the compressor wouldn't engage, the idle wouldn't change, and the fan would not come on. This happened after 2 days of not using A/C. I followed the provided relay on conditions diagram bellow. Jumping the compressor relay engaged the compressor clutch so the clutch worked, I had continuity on the dual pressure sensor so pressure was ok, so only thing I was left with was that the ACCU was popped. I swapped it out with the one on my RS and my A/C kicked on and started working again. The reason for this thread is I would like to know why the original one burned out in the first place. Anyone with an electrical background is most appreciated to lend their time and discover why these things die, given that they are extremely difficult to find. I will share the details with my car:

First everything that is controlled by the ACCU: My car doesn't have a condenser fan, the header that came with the car has the O2 sensor sticking out to were the condenser fan would be and wouldn't be able to fit one in. However the A/C seems to perform well with just the radiator fan on, it blows cold and no issues at idle. Only issue I see is the revs seem to hang for a few seconds when I press the clutch in to shift (When the compressor is engaged).

The fin thermo sensor was severely out of spec, reading 2.7kOhms at 50F weather. 2.7kOhms is the reading it would possibly give at 100F+ weather.

Lastly the revolution pickup sensor was reading 95 ohms at 50F weather.

Would any of these things cause the ACCU to blow out?

Lastly, can the old ACCU be repaired?

Here I added some procedures for anyone out there that is having A/C problems. Source: 1997 Eclipse/ Eclipse Spyder Volume 1 Service Manual

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[petrosian]

Does the ACCU have onboard electrolytic capacitors? I’ve never had to open one of these up before. Maybe this is the next saga in the tales of ECU / TCU capacitor failures

Aside from all the reports and issues we know of for the ECU and TCU, I have a lot of electronics (stereo, A/V stuff) from the 80s and 90s and the electrolytic capacitors (mostly power supply ones) are culprit #1 for issues/failures.

 

[Event Horizon01]

Does the ACCU have onboard electrolytic capacitors? I’ve never had to open one of these up before. Maybe this is the next saga in the tales of ECU / TCU capacitor failures

Aside from all the reports and issues we know of for the ECU and TCU, I have a lot of electronics (stereo, A/V stuff) from the 80s and 90s and the electrolytic capacitors (mostly power supply ones) are culprit #1 for issues/failures.

That was my first thought, these capacitors usually have a useful life of around 20 years and probably popped a few. Its a little difficult to slide the motherboard out of the box without breaking anything but from what I could see there's a few long capacitors sticking out. When I get time to spare I'll see if I can resolder new ones on there and if that revives the board. (First I got to learn to solder ). I'll post results on here when finished. The life of the AC on these cars is purely dictated on this little computer. Makes me wonder why they made it to where the main ecu doesn't control the AC. Its far easier to get one of those than this little thing

 

[jweber]

I’m having same issue on a gsx. I need to try to find a new accu. Car acts almost like ac isn’t even turned on when I command it with switch.