Volvo 850 Electronic Climate Control issues

msdavi59 · Post by **msdavi59** » 08 Jul 2013, 17:03

I have a ’96 Volvo 850 GLT in which the ECC has completely stopped working and the blower fan operates on high speed anytime the ignition is on. Prior to this the unit was functioning well except for intermittent two orange blinking lights on startup. I’d had it diagnosed at the Volvo dealer and they told me there were a number of shorts in the ECC and it was probably on it’s way out. So Thursday when I started the car and the fan went to high speed and the ECC seemed completely dead (no lights, no fan speed control, no AC, no heat and no direction control) I thought, Aha, time to put in the replacement unit which I'd picked up used from the junkyard.

So when I put the replacement unit in, I had the same symptoms; apparently dead ECC and fan on high speed whenever the ignition was on. Now, I admit the used unit I picked up might have the same issue my existing unit has, but it makes me wonder if the problem is outside the ECC. Also, when the dealer told me I had multiple shorts ‘in my ECC’, they made it sound like the ECC was the only problem, but from what I’ve read of the ECC fault codes, most of the shorts seem to occur outside the unit. Is there an OBD-2 reader available to consumers that will read B and C codes, in addition to the P codes that most do (B=Body, C=Chassis, P=Power-train)?

I should also mention that in the past month, my ignition switch seems flaky. When I start the car and release the key, the ABS light stays on (and the car won’t go into gear, headlights won’t work, etc) until I turn the key slightly counterclockwise till the ABS light goes out. Then everything seems to function normally. Could the faulty ignition switch be related to the ECC issues?

Thanks for any insights you can offer - Mike

Post by **abscate** » 08 Jul 2013, 19:24

Definitely replace the ignition switch first before you dive into the ECC.

I would ignore the comment about multiple shorts in the ECC ..do the ignition switch replacement then one back here for component troubleshooting on the ECC...dampers, temp door, fan system

Post by **BEJinFbk** » 08 Jul 2013, 20:33

+1 on a new ignition switch. Checking all of your fuses is also worth a minute or two.

It's also a pretty good idea to search out the diagnostics instructions for your car and
see what those lights are specifically trying to tell you. IIRC, the '86 850's will allow you
to pole those codes with a momentary switch, an LED and a pulldown resistor via the
OBD ll port. There's a post or two around the boards here somewhere...Here's a start:

https://www.matthewsvolvosite.com/search ... &sa=Search

https://www.matthewsvolvosite.com/forums/viewtopic.php?

http://volvospeed.com/vs_forum/topic/47 ... formation/

I suspect anyone that refers to "shorts" when describing an electrical or electronic problem.
The likelyhood is much greater that you had a simple blower motor failure. The motors get old,
the lubrication dries up and their bearings go bad. Then the ECC sees the motor using more power
than it should because of this and warns you with the blinking lights to look into the problem.

The blinkies get ignored, the motor gets worse and eventually burns up the MOSFET in the
power stage. What's a power stage? It's the little chunk of electronics attached to a heatsink
that lives in the heater duct just to the left of your blower motor. It communicates with the
ECC to control the current that operates the blower motor. It's the brawn of the variable
speed blower motor operation. ( FWIW, it often gets called a resistor, even though it isn't.)
But it has limits...

When the power stage fails, it either "shorts" ( Yeah - I said it! ) and the motor just runs at full speed,
or it fails in an "open" state and the motor won't run at all. Either way, it's a very common occurrence.

If the motor has been around for a while, I'd start by pulling it apart and inspecting the bearings.
Lube'em up and reassemble. Then find a new power stage, because you probably need one.

More than likely, that will bring the system back to life.

Post by **jreed** » 09 Jul 2013, 05:05

If it's of use, I wrote up a short guide on building and using a simple ECC code reader. Here is the direct link:
https://www.matthewsvolvosite.com/forums ... 43#p251189

msdavi59 · Post by **msdavi59** » 09 Jul 2013, 08:12

Thanks for all the helpful replies. FWIW, I replaced the blower motor with a new one several weeks ago (the old one was noisy) and all the fuses appear to be OK. My next steps are to build the ECC code reader that jreed suggested (great writeup - thanks!) and replace the ignition switch. Question for jreed...is it easy to interpret the blinking lights...for example, when you refer to "2 1 1" what does this look like....2 short flashes then two long flashes, or something else? Just trying to visualize what I will be looking for.

thanks!

msdavi59 · Post by **msdavi59** » 10 Jul 2013, 17:44

Update - I built the LED code reader suggested by jreed and it works great on all modules except the ECC (OBD-2 connector 6). When connected to connector 6 the LED comes on when I press the push button, but no codes are displayed. In contrast, when connected to other connectors (like 3 for example) the LED blinks when I press the button and then gives me the code afterward (such a 1-1-1).
I thought well maybe this is consistent with the ECC being completely dead because it is getting no power, but I went through the pin voltage tests for the ECC connectors and as far as I can tell they are giving values within range. Most importantly, the ECC seems to be getting voltage and the ground functions. Are the DTC codes stored within the ECC unit or somewhere else? I'm thinking maybe both ECC units I have really are completely dead and thus unable to do anything or return a trouble code?

I'm tending to rule out the ignition switch as from looking at the wiring diagram it has no other function than to supply the ECC power, and power to the back of the ECC does not seem to be a problem.

thanks -Mike

Post by **jreed** » 11 Jul 2013, 05:19

I haven't experienced what you're observing -- a few thoughts:
You might have a 'dead' or damaged ECC unit. Have you opened it up to check for exploded / leaking capacitors (a failure mode others have reported).
Are the connectors on the back of the ECC seated firmly?
The fact that your code reader works to read pin 3 suggests that it is probably OK. On my ECC unit when I push the button, the unit blinks back "1 1 1" when there are no error codes to report.
What type of LED and resistor combination are you using?\

Good luck!

msdavi59 · Post by **msdavi59** » 11 Jul 2013, 09:42

I'm using a 12v LED and a pushbutton switch as shown in the pic. The reader seems to work fine. I get the 1-1-1 code for all modules except the cruise control (where I got a different, but normal code) and he ECC, where I get absolutely nothing. I'd taken a quick look inside the ECC and saw nothing that stood out (burned circuit boards etc) but will take a close look today.
The OBD-2 reader is pretty cool however, even if it hasn't helped on the ECC.

thanks - Mike

msdavi59 · Post by **msdavi59** » 21 Nov 2013, 14:09

Thought I'd post a follow up on this, as I resolved the problem back in July but have been too busy (or too idle :^) to reply.
It turns out that the ECC was at fault. The first one I replaced came out of a pristine 850 in a junkyard...I wondered why it had been junked and now I know possibly why....the ECC had failed. Next visit to the junkyard I made sure to get one from a wrecked 850 to minimize the possibility that a failed ECC was the reason the car was there. This solved my problems and everything works well again. So, to reiterate...neither the malfunctioning (worn) ignition switch nor the heater motor had any bearing on the problem at all, as I didn't think they could as I couldn't see anyway to relate them to the ECC problems I was having based on my reading of the wiring diagrams.
Thanks for all your suggestions.

I think my experience with finding a replacement ECC can be extended to other components like engines or transmissions...make sure the vehicle you get one from has a reason for being in the junkyard that is unrelated to the component you want to replace.

Post by **jreed** » 21 Nov 2013, 18:39

Good tip! I agree! I bought a starter motor out of a crashed '97 GLT sedan (died at ~100K miles) and it tested fine and is now working well in my '97 GLT wagon at 170K miles.