1996 850 Turbo Wagon ECC Works Intermittently

[sandytrean]

This is the first winter that I've had the car, and I've been fighting the heating system on the car for awhile now.
During a long road trip, I discovered that the heater didn't blow hot air. After flushing the system and replacing the thermostat, I found out that the heater core was cracked. It has now been replaced, and it blows hot now.
During this time, I would occasionally get flashing lights from the ECC, indicating a problem in the system. I thought that it was linked to the lack of heat, and it wasn't very common, so I let it slide.
However, now the ECC doesn't work reliably. Sometimes I'll start the car and I get flashing lights, but the fan works, and other times the system won't respond to any input for a few days.
I got the codes read today by the Volvo dealer, and a technician said that I needed to replace the ECC unit itself. I'd rather not do that, since they are so expensive.
The picture shows the codes that the dealer pulled. Do I need to replace the unit?

[kahl]

PM me me your address. I have a serviceable unit you can have for shipping.

[dosbricks]

Welcome to the forum, sandytrean. These are really easy to swap out--in fact, about the easiest thing I ever did to either of our cars. I paid roughly $75 for a used one on ebay, so would not hesitate on kahl's offer.

[scot850]

I'd take kahl's offer if you definitely need the unit. I'm sure the part can fail, but never had one do that. The issues I've had are usually the cabin temp sensors being seized (they clog with dirt over time) and the fan motor/resistor pack failing.

Does the fan work ok in manual mode? When they start to fail, they can become intermittent, and I had one that would slow down on accelerating, and speed up on braking (or the other way around), caused by the bearings in the fan failing and the motor moving allowing it to bind and release.

If the fan is good in manual mode and while driving, then the motor is good.

If the fan is variable when in auto mode it can either be the cabin temp sensor(s) being jammed so the ECC doesn't get a correct signal, or the resistor pack failing/failed.

The cabin temp sensors in the 93 850 I had with ECC were in the headliner hidden behind the grab handles above the front doors. You have to remove the grab handles, the door seal and the plastic trim (if there is one along the top of the door opening on the 850) to get to the motors. You will probably be lucky, and with a good gentle clean and a little light oil the sensor should be good to go again. You can test it before re-fitting to see if the little fan spins. The temperature sensor in the unit can fail. Best place for both this and the ECC (other than kahl very generous offer) is a pick n' pull or auto wreckers. They are usually cheap. I bought a cabin sensor today and an ECC for my stash her in Calgary, and the pair cost $40 CDN.

If cleaning the 2 temp sensors fix the issue then chances are the problem is the ECC unit or the resistor pack.

The ECC system can be a pain as they get older and the plastic parts become brittle. There are plenty of 'fixes' on this forum. Shaft flaps can seize, square driver ends on the flaps can crack allowing the servo motors to turn but not move the flaps, and the servos themselves can break. They are a real pain to get to but with ( a lot!!) of patience they can be replaced without removing the dashboard.

Hope this helps,

Neil.

[kahl]

Unit is on it's way