850 Automatic Climate Control Failure

[slantvaliant]

I have a 1993 850 with the automatic climate control. Recently, the air conditioning quit with a wisp of smoke from the dash and THAT SMELL. I tried to pull the codes at B1, but the light burned constantly when the ignition switch was on, instead of blinking out the codes. Other codes (A2, etc) could be read normally.

I pulled the ECC, which had evidence of smoke from inside the case. Inside, some components have seen serious localized heat to the point of melting the solder. At least one lead is no longer in contact with the PCB. So, it’s toast:

Looks like Ground Zero for the smoke:


Down Under:


Note the lead broken at the solder joint, or possibly "unsoldered" (black/blue component "GZ")


1. When shopping for the ECC, what is the interchange? Are any years/numbers better?
2. The blower resistor, which I also pulled looks OK. Is there a bench test for this while it’s out?
3. What else should I check? I am concerned that something else might have caused the ECC to fail or might have been damaged in the process.
4. Is there a known cause for this failure?

[Ozark Lee]

I think anything '93 to '95 will work for sure. After '95 the vehicle speed signal changed but the ECC gets the speed signal from the instrument cluster. I'm not sure if the analog signal gets converted to a digital signal before it leaves the instrument cluster to go to the ECC or not.

As to the root cause, I think ALPS screwed up and put a couple of the electrolytic capacitors in backwards - opposite the polarity they should be - and after enough years they finally short out. Your PC board looks exactly like all of the others I have seen that have blown up. The schematics for the ECC are not in the public domain so I can't verify that theory.

Historically an ECC failure like yours is not caused by external sources and swapping the controller makes everything work again.

...Lee

[jreed]

The capacitors might have failed due to age -- they dry up, decrease in capacitance, increase in resistance, and may fail themselves or cause a failure in another part of the circuit.
There is a great write up on the how's and the why's on Jim Peisker's blog:
http://volvo850wagon.wordpress.com/tag/electrolytic/

I'm thinking that I will pull out my ECC unit and replace all the electrolytic capacitors in it soon, before they fail. I've already done the Fuel Pump Relay, the intermittent wiper relay and the emergency flasher switch. Some background reading on the fuel pump relay capacitors can be found here:
https://www.matthewsvolvosite.com/forums ... =1&t=33696
https://www.matthewsvolvosite.com/forums ... hp?t=13806


"Capacitors are electronic components which give physical manifestation of the fundamental electrical property of capacitance. They are used for timing, charge storage, and filtering, among other things. Electrolytic capacitors use a solid (more expensive) or liquid (cheap and common) electrolyte material to enable relatively large capacitance in a small area. Aluminum electrolytic capacitors, such as used in the fuel pump relay, have a limited life. The liquid electrolyte degrades with temperature (hot and cold), applied voltage vs. rated voltage, current flow, and just plain time (they even have a non-operating shelf life). Quality electrolyte solution is also a factor; better electrolytes cost more but cheap ones are often used to save money.

When the electrolyte degrades it decreases capacitance and increases internal resistance; both bad for most circuits. The circuits they are part of start to behave badly and may fail completely.

Sometimes electrolytics can be diagnosed visually because they bulge or leak their chemical contents. However, as in this case, the caps were bad but looked fine. It requires instruments to properly check old caps that pass visual inspection. Besides, 15-year old caps should be replaced just based on age.

Electrolytic caps with higher temperature ratings last longer. A higher voltage capacitor can always be used in any circuit and that makes it last longer as well, but they tend to grow in size with voltage, so space may limit the size of the part."

[mikealder]

It looks like a large zenner diode has broken away from the PCB (last picture), I think it's a zenner because of the "Z" that can be read on the body of the component, these are usually employed to clamp a voltage to something lower than the supply voltage. Once it breaks away the PCB will have been subjected to higher than intended voltage which could be responsible for blowing the caps - Eitherway it is shot and beyond repair, best shop around for a replacement - Mike

[jreed]

Great observation! That makes sense. I wonder what would cause the lead on the Zener diode to pull out of the thru hole?

[abscate]

Components are often stuffed into Boards under some tension - when the solder gets hot enough and melts, they often spring loose.

Component level repair on that Board is possible but I would not recommend based on the visual.

Pick and Pull beckons...

MMMMM...I think Im going to open a chicken and pork fast food place called

Peck and Pull with free Volvo parts

[jreed]

I replaced the electrolytic capacitors in my ECC unit yesterday (this is from a 1997 Volvo 850 GLT wagon at 167K miles). The originals in the ECC were Nichicon PF series (which has been superseded by the PJ series). I replaced them with Panasonic FC series, which have a higher ripple current rating (approximately 2x higher) than the PJ series.
I got all the capacitors at DigiKey. If your ECC is the same as mine, you're going to need qty 1 1uF/50V, qty 5 4.7uF/50V, qty 2 100uF/25V, qty 1 220uF/50V and qty 1 3.3uF/50V. The FC series doesn't come in 3.3uF size, so I got that size in the EB series, which doesn't rate as highly in ripple current but does have a long life rating at 105C.
I would recommend taking a look inside your ECC unit to identify the capacitors you will need to replace -- the capacitors may be different than what is listed here.


Part Number Description Quantity Price Extended Price
P10312-ND CAP ALUM 1.0UF 50V 20% RADIAL 1 0.33000 $0.33
P10315-ND CAP ALUM 4.7UF 50V 20% RADIAL 5 0.33000 $1.65
P10269-ND CAP ALUM 100UF 25V 20% RADIAL 2 0.34000 $0.68
P10326-ND CAP ALUM 220UF 50V 20% RADIAL 1 1.03000 $1.03

Here's a link to the large 220uF, 50V part:
http://www.digikey.com/product-search/e ... ND&x=0&y=0

[Ozark Lee]

This almost needs to go on the stage zero list.

I love component level repairs, especially when they are preemptive - nicely done.

...Lee

[jreed]

Thanks!
I measured the old capacitors today for capacitance only (I don't have an Equivalent Series Resistance [ESR] tester). Here is what I found (each measured value is the average of three readings):
Cap #     Specified [uF]      Measured [uF]
1               220                         209
2               100                         97
3               100                         102
4                4.7                         4.8
5                4.7                         4.7
6                4.7                         4.8
7                4.7                         4.7
8                4.7                         4.7
9                3.3                         3.3
10               1.0                         0.9
Note: I don't know what the accuracy or calibration of the capacitance meter is. If I assume that it's OK (and the results for caps #4 through #9 are very close to the specified values), then it looks as if the big 220uF cap had decreased the most, at about -5% from specified, which is still within the typical +/-20% tolerance for electrolytic capacitors. So, no big deviations from the expected values... not bad after 17 years of use. Of course, from what I've read the ESR might tell a different story -- it can find dried up capacitors that still test good for rated capacitance but measure high for resistance.

[abscate]

Not relevant for the 1990s, but from 1999-2002 there was a huge issue with "capacitor plague" as a result of failed industrial espionage....