Isn't there an ECC diagnosis thread somewhere?

urbex · Post by **urbex** » 02 Aug 2011, 20:48

Thought I had bookmarked a link somewhere that showed a procedure to determine failure points in the ECC circuits, but now I can't find it.

Problem - '94 850 with the electronic climate control (has auto settings). Been dealing with the squealing temp sensor on the passenger side for months, shooting it with canned air didn't do squat. I've been meaning to pull it out, and keep forgetting. Frequently got the blinking AC/REC lights, always assumed it was due to that, as the system worked without issue otherwise.

About a month ago, the blower fan would randomly stop working at high speed, and would top out at a slow speed. Oddly, when attempting to control the fan manually, as opposed to the auto setting, I could hear the fan speeding up and slowing as I moved the slider back and forth, but even when the slider was full right, the blower was still spinning slowly and I could barely feel the air coming out of the vents (going down the road at 25mph pushed more air through the vents than the blower did while stationary).

About a week ago, the blower quit altogether, and I got the flashing lights as soon as I turned the car on, regardless of fan switch position, even off.

I swapped in a known good blower, no change. Pulled the transistor from the power stage and tested it, it's functioning properly. For giggles, I replaced the transistor anyways, and the blower still isn't working.

I did noticed after all this swapping, if I turn the car on when the fan switch set to off, the lights do not blink, but do start blinking as soon as I slide the fan switch to either auto or somewhere in the manual mode.

I'm thinking I probably have a bad connection somewhere, but I'm not 100% sure where I should be looking, or what the diagnostic procedure is from here other than trying things randomly or using the "throw parts at it until it's fixed" method

Post by **Ozark Lee** » 03 Aug 2011, 00:16

The unit should be posting error codes via port B-1.

For all of the troubleshooting procedures see the factory manual:

https://www.matthewsvolvosite.com/downlo ... vo_850.zip

Once you unzip it see the file named AC Heater System Auto.pdf

Without codes all we can do is guess.

...Lee

urbex · Post by **urbex** » 22 Aug 2011, 17:38

Finally had a chance to play with the car today. I pulled the power stage and reconnected it (pull/replace connectors) and replaced the wiring bundle support. After this I got the fan back, but it didn't seem to be running at full speed like it should (same as before - still variable speed, but never blew as hard as it used to). Just for giggles, I swapped the blower motor with another I had tested good by applying 12VDC directly to it. After I had nothing but the flashing lights again.

Pulled the codes, had 4-1-4, 4-1-8, 4-1-9. Cleared the codes, turn ignition off/on, and got nothing but flashing lights again. Pulled codes again, only got 4-1-8 this time.

I went through the factory manual, but it shows using the test box behind the ECC, which I don't have. I've done the outside temp sensor tests, both within spec. All the other tests show testing either pins on the test box, or continuity between a connector and one or more pins on the test box...which leave me in the dark on those. I suspect it's faulty wiring between the ECC and the power stage, but then I'm not sure where I should be checking.

I also did notice that I can hear the damper motors turning when I adjust temp control knobs, or air position knob. The AC switch also works to turn on the compressor, as does moving the air selector to defrost.

Post by **misha** » 26 Aug 2011, 13:32

Here's the code list:

code list 850 turbo.pdf: (44.99 KiB) Downloaded 236 times

urbex · Post by **urbex** » 12 Sep 2011, 21:20

just to update as solved, turned out to be a power stage failure. Picked up another at my monthly junk yard trip today, plugged it in, and the blower now works as it should on all speeds. Still have an issue with the driver's side temp sensor, code 124 I think, saying circuit open or shorted to 12 volts, IIRC. The fan spins for a second or two when I first turn the ignition to run, but it's also from the junkyard, so it might be a faulty one as well. I'll swap it with the passenger side one some time later this week to see if the code follows to the passenger side. So my auto setting, while it works, and turns the blower on, it only runs at full blast. Minor inconvenience, really.

Burn-E · Post by **Burn-E** » 13 Sep 2011, 15:18

When you say you replaced "the wiring bundle support" for the power stage what exactly did you do? Do you mean you simply reconnected it to the power stage or did you actually swap out the wiring?

I'm assuming it was the case that the power stage wasn't tightly connected to the wired connector and so it wasn't getting power so when you reconnected it the connection was fully established and the fan then ran?