S/V/C V90 A/C issues

Yesterday morning the a/c was blowing nice cold air until I got about 2 miles from work. I wondered if it was the clutch gap or thermal switch but checked both of them when I got home and they are not the issue. I tested the fuse and relay under the hood and both are good but there is no power to the compressor or either of the pressure switches. Now I am a bit lost. The lights on the control panel light up as if it is working, no flashing or anything of the sort. It was over 110 degrees in the car all the way home yesterday and I really want to get this figured out soon. ECC controller under the dash?

Thanks in advance!

Ugh, it's hot!!

Most likely an issue inside the ECC control panel, failed solder joint would be primary suspect. With the AC switched on, slap the dash near the control panel, might get you working temporarily. IINM (WARNING: IINM!!) otherwise to bypass the ECC, I think you have to access the connector off the pressure sensor at the dryer, and apply 12v+ to the Brown-Green wire. This will allow the sensor to tell the Motronic fuel computer to turn on the compressor relay (2/22 in the relay box under the hood), compressor should cycle normally. If not make sure fuse 11B/16 (same location as relay) is good.

Only a tiny amount of power is required at the brown-green wire, this is just a signal to the fuel computer. So a tiny wire stripped and placed over the related male sensor terminal while you push the connector back on, should be enough.

Okay thanks, good to know. I didn't realize these were prone to fail. I think I may have kept one out of a 93 940 parts car, but finding it in the recently relocated garage would be a chore! But I could swing by t jy and pick up a replacement prretty easily, too.

I'm definitely down for giving it a good slap this afternoon to see if it will work!

By the way, what's the word on taking the control panel apart and re-flowing the bad solder joint?

Thanks again!!

No dice on getting it to work with brute force. Temps 102-105? all this week, I'm to old for this.

Anyone ever converted one of these to MCC successfully?

Just grabbed a code from the ECC, code 1-6-1 Solar Sensor. Really?

Sensor was good, I had forgotten to shine a light onto it when I pulled the codes. I still have zero fault codes and even tried a different ecc controller out of a different car. No change. Thoroughly annoyed at this point. I have no idea what to check next.

Still chasing this same problem. Talking to myself here I think.

Tore down both controllers that I had. Was sure I had found bad solder joints on both of them so I reflowed them both. Tried them both in the car and still same result. I have power to my high pressure switch and when I unplug it, the cooling fan comes on high. When I plug or unplug the low pressure switch, there is a change in idle so even though my caveman era test light shows no power, I know I have a signal there after all. I even tried the positive wire jump to the brown-green wire and I get nothing. But if I unplug the connector at the compressor itself and apply 12v, it comes on and starts pumping freon through the system. I have gone so far as to pull the vacuum controller as well and check/reflow all of the joints on it as well with the same result. Freon level in the system is good, clutch is good, compressor sounds as if brand new with whisper quiet operation. Underhood fuse and relay are both good and the function of the relay itself has been verified as good. I also pulled the temp sensor out of the dome light, cleaned it, confirmed vacuum to it and reinstalled it.
I have a loss of continuity somewhere in the system and cannot seem to find it. I have searched every corner of the internet, downloaded wiring diagrams and still know that there is some stupid simple thing in this car that is keeping this from working. What it is, is just beyond me....