With my 1994 850 Turbo, I've got several error codes for the climate control system (acquired via port B1). At first, my mechanic suggested it was most likely the ECC unit itself, so I scored a supposedly working one off eBay, and nothing changed. Instead, I got some more error codes, but fewer and different ones. The one thing that's consistent is that with both units, the air only blows in your face--the air distribution dial doesn't do anything to affect air flow. The LEDs by the AC and REC switches flash. The AC doesn't work at all, which could be related, or maybe not.

Here's a video demo I made, showing the troublesome behavior:

The error codes for the original unit:
126 Passenger’s side interior temperature sensor open circuit or shorted to 12 volts
132 Driver’s side air duct temperature sensor open circuit or shorted to 12 volts
134 Passenger’s side air duct temperature sensor open circuit or shorted to 12 volts
145 Faulty signal from function selector switch
231 Ventilation damper motor position sensor open circuit or shorted to 12 volts
324 Floor/defrost damper motor active too long
411 Blower fan seized or drawing excessive current
413 No control voltage at driver’s side interior temperature sensor inlet fan
414 Driver’s side interior temperature sensor inlet fan seized
416 No control voltage at passenger’s side interior temperature sensor inlet fan
417 Passenger’s side interior temperature inlet fan seized
418 No control signal to blower fan power stage

Here's the error codes for the replacement unit, which came from a '95 850 Turbo:
126 Passenger’s side interior temperature sensor open circuit or shorted to 12 volts
211 Driver’s side damper motor position sensor open circuit or shorted to 12 volts
221 Passenger’s side damper motor position sensor open circuit or shorted to 12 volts
231 Ventilation damper motor position sensor open circuit or shorted to 12 volts
235 Recirculation damper motor position sensor open circuit or shorted to 12 volts
321 Driver’s side damper motor active too long
322 Passenger’s side damper motor active too long
325 Recirculation damper motor active too long
414 Driver’s side interior temperature sensor inlet fan seized
417 Passenger’s side interior temperature inlet fan seized

So, different codes, but same net result--the thing doesn't function properly. I've read that it could be an open ground somewhere, and I know there's ways to get more specific in testing. I tried going through this doc:

http://www.volvoclub.org.uk/tech/ser...ystem-Auto.pdf

But I didn't make any headway, as I'm out of my depth with this electrical system troubleshooting. Any ideas about a good next step? I'm going to return the ECC unit I bought, as it seems like a waste of money now. Thanks for any input, it's much appreciated.

 

Does the heat or AC work? I hear the fan running.

The system has motors that control the air flow through the vents. If the fan is running and the cage is still attached, air flow is going somewhere. If the dash is busted away from the firewall, air can be escaping from the broken gaping holes from the dash mounts.

So, if the fan is blowing and cage is still attached, air is blowing through a vent somewhere. If you pull the glove box you can see those motors that control the flaps within the duct system to direct air to the selected vents. So, chances are, a motor or two is bad.

If the temp sensors are seized or bad you will get the error but it should not stop the air from flowing.

 

"Does the heat or AC work? I hear the fan running."

The heat works, but the AC does not.

 

Well, does the compressor kick on when you turn the AC on?

 

No, it doesn't seem like it's coming on.

 

It is a visual check. You turn the system on and look at the front of the AC compressor. If the very front of the compressor is spinning, it is working, if it is not spinning, it is not working.

 

Ah, I see. No, it's not spinning.

 

"if the fan is blowing and cage is still attached"

I'm not sure what the cage is, what are you referencing?