850 Automatic Climate Control Possessed

Vanillagrila · Post by **Vanillagrila** » 12 Mar 2016, 13:26

Hi Guys,

I am reaching out in absolute desperation in the hopes to save my beloved '95 850 Wagon. I sincerely appreciate any guidance you can provide. Now... to the details:

Two weeks ago, while stopped at a light, my blower motor came on at full speed, full hot (ECC controls and LED's went dead). My first though was that the transistor in the blower module had packed it in, until later that afternoon on my return from work, the climate control started operating normally. Everything was fine for a few days until, this time, my ECC went dead again, except this time, fan would fail OFF, and only for a few seconds at a time.

At this point I decided to pull the codes from the ECC using the diagnostic blink codes. I saw about 40 or so codes, which I can only assume are nuisance codes since the system was working fine (aside from the intermittent failures of the system). I cleared the codes and drove the car until the ECC died again, and checked the codes hoping to see something. I got code 1-1-1 (no faults found).

This left me to believe that the ECC had packed it in, and so started my search for a replacement. Most of the junkyards in our area had either been picked though, or the cars crushed because they are too old and not that common. The dealership told me they were obsolete and that their repair shop would not touch it because it was too old. They offered to find me a used one for $320, but instead, I ordered one from eBay for $110. After ordering the replacement the ECC failed again back to full speed, full hot. Replaced the ECC with the eBay unit and the problem remains.

Today I removed the blower control module, and decided to replace the MOSFET on spec, hoping that this might be the problem. Unfortunately, I am still driving around in Winter in Canada with my windows open because my car is scorching inside.

So right now, I'm in a position where I am troubleshooting a problem with 3 components (my ECC, eBay ECC, and my Blower Module) that I can not verify are working correctly. The blower module had a circuit board associated with it which controls the MOSFET, so I'm not sure if that is faulty, even after replacing the MOSFET.

I replaced the blower motor 2 years ago with an aftermarket, but kept my old squeaky motor and re-installed it just to confirm the motor wasn't maybe pulling too much current for the ECC but it was the same (full speed).

I did the obvious stuff like checking the harnesses and connectors and everything looks like its brand new.

So where do you guys recommend I go from here? Replace the blower module for $150? Try another ECC? Or just drive with the windows open?

Thanks in advance for any input!

Post by **kahl** » 12 Mar 2016, 14:27

I am betting your ECC is the problem. There has to be another 850 floating around your area that has a enlightened owner that would let you put in your ECC in his car and check for operation.

Post by **scot850** » 12 Mar 2016, 16:43

Have you checked and cleaned the 2 cabin temp control units (1 each side behind the grab handle in the roof above the front doors)?

Most folks never check these and they collect dirt and crap over the years until they get clogged and can't sense any longer.

To remove them you need to remove the screws holding the grab handles in place and pull down the door surround seal to allow you to get to the sensors.

Remove them and carefully clean with IPS and cotton buds and then give the little fan unit a small spray with silicon oil and chances are you will be good to go again.

Neil.

Post by **jreed** » 13 Mar 2016, 08:27

I agree with the above advice from scot850 to check the sensors.
The symptoms you described of intermittent full hot, full speed fan, failure of the ECC LEDs to light and failure to respond to dial controls could be indicating that you have one or even two failed ECC's, though it seems less likely that both could be bad.
In the past, some posters on MVS have reported that they found burned up electrolytic capacitors and other components on the ECC board. It might be worth opening up both of the ECC's to inspect them for visible damage. When you swapped in the second eBay ECC, did you notice any difference in the symptoms?

Vanillagrila · Post by **Vanillagrila** » 13 Mar 2016, 09:44

Hey Guys. Thanks for your replies!

I haven't had a chance to check those sensors yet, but I plan to within the next few hours and I'll be sure to report back my findings.

As for my ECC having leaky capacitors, I did inspect the board inside. I'm almost ashamed to admit it but I'm a professional electronics technician (asking for help with my tail between my legs

), and none of the capacitors showed any sign of leaks or other damage. We did throw the board under a microscope and found a small solder blob that might have been shorting to another trace. Cleaning this did not change the problem one bit.

As for the eBay ECC, I have not taken it apart to have a look on account that I may try to return it for refund. The seller on eBay had previously sold 20 of these units, and he marked the screws so that disassembly would void warranty. My faith in the seller might be misguided, but he seems to specialize in these units and guaranteed they would be serviceable.

When I first tried the eBay ECC, the fan seemed to work properly for maybe a second, then we went straight to full fan, full hot. The only difference between the units is that the REC LED stays illuminated on the eBay unit, where as on mine they were all extinguished.

I will report back once I've checked the cabin temp sensors. Thanks again!

Vanillagrila · Post by **Vanillagrila** » 13 Mar 2016, 13:35

Update:

I removed the 2 cabin air sensors above the front doors and, thought they were dusty, are they are working properly. Even with the ECC completely dead, the ECC is still driving the small fan motors on both sensors. I took the time to measure the resistance of all 5 temp sensors and they seem to be ok (cabin temp at 17.4k - 17.9k ohms respectively, and the duct/ambient sensors measuring 19.0k-19.3k ohms). I also took the time to measure the 5 servo motors (70.0-71.3 ohms) and their servo position potentiometers (which were all about 2k-4k ohms and obviously not going to be comparable because they are all potentially in different positions). I then completed a continuity check between the ECC and the Blower Control Module, and even tested the solar sensor. Everything checked out fine. I should mention that all of these measurements were taken at the ECC to eliminate any doubt about the wiring between the ECC and the sensors.

Both ECCs are now either on full fan, or no fan, with no AC or REC lights. As the subject says, this thing is possessed.

If anyone has anything else that I should check, I am open to trying anything at this point. My fear is that if I try another ECC, and it turns out the Blower Module is faulty and causing the ECC to go tits up, then I'm gonna be sourcing a fourth ECC. I am grateful for the help.

Post by **scot850** » 13 Mar 2016, 13:44

This sounds more like the resistor pack has failed. It is all or nothing which is usually a good sign.

These are usually easy to find at PnP as most people don't bother to take them. If you have no luck, PM me as I have a bunch of them. Just changed one on my car after it had been standing after a long re-build it decided too immediately fail.

Neil.

Vanillagrila · Post by **Vanillagrila** » 13 Mar 2016, 16:29

Thanks Neil. I'll keep you in mind. I might try and source one locally first in the hopes that I get my heat working by the end of the week.

Post by **scot850** » 13 Mar 2016, 16:48

I may take a run to our local PnP's later this week as they have a member sale of 20% upwards depending on amount spent.

There are 2 x 850's showing, don't know what they have left in them, but for example and ECC unit is about $30 CDN less any discounts if you need another for your collection.

Neil.

Vanillagrila · Post by **Vanillagrila** » 14 Mar 2016, 10:52

Update:

So I tried powering both of my ECCs with a power supply (Pins A1-12v, A6-GND), and neither one has the REC and AC lights come on. Is it possible that a faulty Blower Module could have fried the ECCs?