'94 850 ECC madness.

IG-88A · Post by **IG-88A** » 21 Feb 2020, 04:59

I've been trying to figure this out for the past couple of years, and I'd honestly given up. A couple of years back, I had the 'fan running on high at all settings' problem. I replaced the resistor (genuine Volvo) and the blower itself at the time. When I reinstalled the ECC unit itself, it wouldn't work. So I swapped in the one from the other 850. When I did that, the cabin filled with an acrid smell and that unit stopped working too. Even when I swapped it back into the other car. I purchased a unit off ebay that worked fine at first. But then I got what seems to be no movement from the flaps themselves. Air just seeps out of all vents. I can't control flow to various vents at all, and the airflow seems obstructed. On some occasions, during cold weather, the driver's side vent will seep cold air even after the car is warm. If I turn the car off and restart it at a stop sign or something, it fixes itself and will actually respond to the temp setting. But the problem of not really getting any air flow and not being able to change any air flow setting remains. On one occasion, when I started the car, the blower fan sounded as if it was hitting on something as it spun. It did this for maybe 30 secons then stopped, never to return again. I don't know what that could have been or if it's somehow related at all. I'd also like to know how the ECC units I've tried to use in the car have either died instantaneously, or in the case of the existing one, worked fine at first and then messed up.

I'd really like to get this sorted out. But I can never seem to find any DIYs, troubleshooting, or concise articles on how to diagnose and fix the ECC system as a whole. the connecting arms, servos, etc. I have read that there are some very nitpicky calibration procedures. And I think I recall reading that if you don't calibrate them properly, things will get even more screwed up. But in everything I read, all I see is people blaming the resistor or the motor and that's where the trail goes cold. Does anyone have any solid advice or info on this issue? How I wish they made a Bentley manual for these things. Haynes and Chilton are okay. But I know a Bentley would be a lifesaver for this system.

Post by **RickHaleParker** » 21 Feb 2020, 13:06

You got to be careful swamping ECCs on the 850. There are ten different versions of the 850 ECC, not all are interchangeable. Going from one version to another may require some rewiring. Read and study this thread.

IG-88A · Post by **IG-88A** » 22 Feb 2020, 04:24

RickHaleParker, that's great news! And just the type of info I've been needing! Now to figure out what ECC module(s) I need to source. Now it's a matter of figuring out which ones came from which car originally. I should have labeled them. This should solve a lot of issues once I sort it out. Thanks a lot!