Electrical glitches on 96 850 GLT non turbo

luismedina · Post by **luismedina** » 07 Sep 2008, 13:25

Hi everyone! I'm a new member, and allow me to congratulate you on this awesome site.

Here's the deal:

We own a 1996 Volvo 850 GLT wagon, non turbo, with 56k miles on it. We are the second owners and the car was fine until about a year ago when the power locks started acting up: they would open and close while the car was moving, intermittently but constantly. We took it to the Volvo dealer to get it fixed and after paying them about 600 dlls for changing a "relay", it was faulty the next day. It was very dissapointing because we thought nobody could do a better job than the manufacturers. Anyway, we took it back but they said it could be anything and we'd have to pay again for what they didn't fix.

So my brother had a guy disable the power locks, and gave us peace for a while. A couple of months later, the sunroof started acting up: first it wouldn't close, then, when closed, it would open to the vent position without touching the switch, all while driving. Finally, it just opens on its own while driving, and after I close it, it'll open itself again at his will.
Next thing that happened was the speedometer panel lighting went off when driving at night, and I just recently discovered that as long as I push the sunroof switch to the "open position" they will come back on. Obviously, I can't be pushing the button all the time!
I checked all the fuses in the box, and besides the power doorlock one, all of them are fine (I mean the fuse isn't blown).

We took it to a mechanic to hook up the OBDII and see if it showed any codes, but no such luck, nothing came back.

I hope you guys can provide some insight as to the best way to aproach this issue

Thanks for your help, hope to hear from you soon!

850FLA · Post by **850FLA** » 07 Sep 2008, 15:26

I'm not big on electrical issues but it sounds like a short somewhere. It could also be a faulty ground wire. Once cars age over say 10 years it is a good idea to check all visible grounds and clean them carefully. You would be surprised how things will improve.

As far as it being a fuse...I don't think it's a fuse issue.

Post by **Ozark Lee** » 07 Sep 2008, 15:45

It sounds like you have a problem in the wiring harness under the dash. The instrument panel lights and the sunroof controls have nothing to do with each other beyond the lamp in the sunroof switch. There is no easy way to track these kinds of problems down beyond grabbing the schematics and checking from point to point. The most likely places are anywhere near something sharp such as the steering column support braces.

There is a comprehensive service manual pinned on the site here:

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

Once you unzip it see the file named system wiring diagrams.pdf. The diagrams call out the wire colors and they can be traced back through the harness. Since the sunroof switch is common to at least two of your problems I would start tracing from that switch.

A more comprehensive electrical manual can be downloaded here. It shows the location of the junction points but it is more of a headache to use.

http://volvo.techno.org.pl/schematy.html

It is a Polish site but the manuals are in English.

Has anything aftermarket ever been added to the car? A lot of aftermarket installers can make a real mess of the wiring by either drilling screws through the harness or just butchering things by tapping in to the existing wires.

This may be a difficult problem to find but it will be relatively easy to fix after you find it.

...Lee

BobD · Post by **BobD** » 07 Sep 2008, 17:44

Lee has the answer. All of the things that are causing you issues (Power locks, sunroof, and IP lights) run in the same wire harness bundle. When you energize the sunroof switch you are cross feeding into the instrument panel light circuit which has probably been broken from it's normal power supply. The fact that it happens while you are driving is probably from bare or cracked wires that touch together under vibration acting like a switch closure. The Polish site Lee listed has the schematics needed to chase down any electrical problem. It includes pictures showing where the bundles are run, where the connectors are, functional diagrams, and the connector pinouts. Its a slow and laborious process, but you have to take the switches out of the dash, disconnect them and start seeing what is connected together and what is shorting to ground. Then you can either pull the dash and fix the wire harness or take tha lazy man's route like I did and just route some new wires.
Good luck.

850FLA · Post by **850FLA** » 07 Sep 2008, 18:17

BobD wrote:Lee has the answer. All of the things that are causing you issues (Power locks, sunroof, and IP lights) run in the same wire harness bundle. When you energize the sunroof switch you are cross feeding into the instrument panel light circuit which has probably been broken from it's normal power supply. The fact that it happens while you are driving is probably from bare or cracked wires that touch together under vibration acting like a switch closure. The Polish site Lee listed has the schematics needed to chase down any electrical problem. It includes pictures showing where the bundles are run, where the connectors are, functional diagrams, and the connector pinouts. Its a slow and laborious process, but you have to take the switches out of the dash, disconnect them and start seeing what is connected together and what is shorting to ground. Then you can either pull the dash and fix the wire harness or take tha lazy man's route like I did and just route some new wires.
Good luck.

More commonly known as a "short"

Just as I said in the first response.

luismedina · Post by **luismedina** » 07 Sep 2008, 18:44

Thanks guys,

I'll download the manuals from the site and start working on it. It'll probably take me a while, but I think I'll be able to pull it off.

I'll be checking to see if anyone's got more ideas, and to let you know about the progress.

Thanks again!