Another Car, Another Climate Issue. AC This Time. Topic is solved

[xanthefin]

Did throw via update more Motronic AC brain thinking at Live.

One slightly off.. but on one ECM Volvo does prevent Climate Control Compressor working if ECT is over 125C (257 F).

[V50M66]

Ok, here’s an odd one. Cleared the codes for everything for unrelated reasons, and the AC works! Kind of.

See, it’ll work and the compressor will engage for a few mins. It will then abruptly click off and not re-engage unless left to sit for a while.

I bypassed all the thermal switches, thinking these were my issue, but it hasn’t changed anything. No, it’s not the clutch spacing - the compressor clutch stops seeing power.

Even more odd, when I attempt to jumper the pins in the fuse box, the compressor does not engage until I let it cool down

[scot850]

Question on MCC system:

Does the MCC system have a cabin temp sensor at all or is it fully Manual? Sorry, can't find much on the MCC system.

Does it have the inline temp sensor just to the left of the cabin cold air intake?

Neil.

[V50M66]

And just like that, it’s fixed! Finally.

No temp sensors on MCC as far as I can tell. It’s really archaic.

Reading through my symptoms, it seemed a whole lot like a really exaggerated case of the compressor clutch needing shimming, so I shimmed the compressor anyway, figuring it can’t hurt.

In the process, I learned that the clutch gap was so far out of spec that the compressor oftentimes wouldn’t engage with power going to it. Shimmed it with lots of extra-thick zip ties, and it engages properly now. Filled the system and she’s nice and frosty. So glad this car has working AC after all this. At least it didn’t really cost me anything aside from time and headache.

[scot850]

Glad it turned out to be something simple in the end! Kudos for going back and rechecking!

Neil.