1993 Volvo 850 Heater Core Leak, ACC Failure?

alexk243 · Post by **alexk243** » 22 Jun 2014, 21:54

So I recently noticed a coolant loss, sweet smell in my car and damp carpets that were sticky, aka a heater core leak. I still had to get home so I was running the fan to keep air flowing and when the heat turned on (car starting to overheat) it shot out moisture/smell so I quickly turned off heat and let the car sit at my house.

Today I got to fix it and when I start the car up the system smokes and steams again (car was really warm) and there is smoke and a burning electrical smell and the fan gives out.

Popped open the ACC as I am fixing my car it appear to have shorted (posting pictures).

Is it shot? Repairable? Anything else that may have gone?

I a simply bypassing the heater core in the engine compartment for now, heater core is drained. Will replace later, but I would like the climate control (AC, Fan) to function now.

alexk243 · Post by **alexk243** » 22 Jun 2014, 21:58

Front side of the chip:

alexk243 · Post by **alexk243** » 22 Jun 2014, 21:59

And the backside of the chip:

Post by **abscate** » 23 Jun 2014, 03:48

Board level repairs are a tough place to start in electronics. I would ebay or pick and pull a used unit and replace the whole thing. It might help fixing the old one with a good one side by side.

Repairing burnt traces on a board is tough..maybe 25% success rate IMHO.

Post by **Ben850** » 23 Jun 2014, 04:59

It is the capacitors that have burnt up. The first three of those four in the picture are the ones that burn.
There is a thread where someone has replaced them with success, but the '95 to '97 ECC does not use the capacitors and is more of a solid state unit.
That is what I had switched to my '93.

alexk243 · Post by **alexk243** » 23 Jun 2014, 09:23

Would a 95-97 ACC controller work in my 93?

alexk243 · Post by **alexk243** » 23 Jun 2014, 09:27

Also, is there a chance that other items were damaged in this leak? fan, fan resistor?

Post by **Ben850** » 23 Jun 2014, 15:30

alexk243 wrote:Would a 95-97 ACC controller work in my 93?

Yes. I have a '96 in mine.
I don't think the leak is what caused your ECC unit to fail. They just do. The ones of that configuration seem to all fail sooner or later.

Search some threads, there are a few, for ECC failure or the like. There is more information that I have already forgotten than I still know.

alexk243 · Post by **alexk243** » 23 Jun 2014, 17:57

Well I grabbed one for $26 at a junkyard today, installed it and it works fine, no issues. Guess it was just random.

Post by **jreed** » 24 Jun 2014, 05:11

Glad you got your system working with a replacement unit!

Just wanted to share a photo of the internals of the ECC unit from my '97 855. It definitely doesn't have the row of smaller electrolytic capacitors that burned up in your '93 ECC unit. In place of the capacitors there is now a row of diodes (D111, D106, D112, D107, D115, ...). The board looks to have been redesigned.

I went through this board last year and replaced all the old Nichicon electrolytic capacitors with new high temperature, low ESR Panasonic caps.