Instrument Panel Lights Failed. '92 940 2.0L

[trebor]

Originally Posted by Laird Scooby

The blue is the earth for the dimmer illumination. Have a look at pg 38 (by document viewer number) of this pdf :

http://www.myvolvolibrary.info/Tech_...C842%2Cnull%5D

In other words, the blue has nothing to do with your problem so you can ignore it.

However, if i've understood you correctly, if you take theblack wire directly to earth, the instrument lights work?

Thanks for that PDF - extremely useful indeed!

From looking at the diagram, I can see that the blue wire (which is the output from the brightness controller, or "rheo" as its labelled) comes into the brightness adjuster module to light the internal light for the adjuster itself. This light is dead on my Volvo (perhaps just a blown bulb) so I hadn't considered it. The confusion comes however with the white cable being the other side of the light _and_ the input into the adjuster.

The supply to all the illumination lamps is between white (presumably +12V) and blue. By connecting blue to black (0V) I've effectively shorted out the "rheo".

Now I still don't know where the fault is: the brightness adjuster measured what I would've thought are sensible resistance readings (around 1k Ohm) but these could be out; or it could be that the fault is in the control unit behind the instrument panel.

Without some known-good readings to compare against I'm kind of shooting in the dark here...

[Laird Scooby]

Originally Posted by trebor

Thanks for that PDF - extremely useful indeed!

From looking at the diagram, I can see that the blue wire (which is the output from the brightness controller, or "rheo" as its labelled) comes into the brightness adjuster module to light the internal light for the adjuster itself. This light is dead on my Volvo (perhaps just a blown bulb) so I hadn't considered it. The confusion comes however with the white cable being the other side of the light _and_ the input into the adjuster.

The supply to all the illumination lamps is between white (presumably +12V) and blue. By connecting blue to black (0V) I've effectively shorted out the "rheo".

Now I still don't know where the fault is: the brightness adjuster measured what I would've thought are sensible resistance readings (around 1k Ohm) but these could be out; or it could be that the fault is in the control unit behind the instrument panel.

Without some known-good readings to compare against I'm kind of shooting in the dark here...

No, the blue wire is NOT the output, it's nothing to do with it! Ignore the blue wire, pretend it doesn't exist!

The output is the green/brown wire from the wiper of the pot. The black wire is the earth from the pot via a resistor between the pot and the black wire.

The +12V feed to the pot is indeed the white wire, again this goes through a resistor to the pot.

There is a blue earth wire coming from the brightness controller (RHEO in the diagram), the +12V feed into the RHEO unit is on another white wire and there is a brown earth wire from the RHEO unit too.

The RHEO unit and the pot share a common earth, 31/10.This is on the drivers kick panel and is what i refer to as an MEP - Multiple Earth Point, look at Pg191 of the pdf to see it. Could be worth cleaning and tightening the connectors on it.

[trebor]

Major bad news: my Volvo was hit by a drunk driver and is now a complete write-off! :'(





Luckily nobody was hurt.

So my 10+ years of being a Volvo 940 owner have come to an abrupt end. Probably I'll be on the lookout for another one soon...

[MiniNinjaRob]

Wow that looks awful - glad everyone is ok.

At least you don't have to fix the dashboard now.... small consolation I know!

[bluebrickrick]

Ouch, that looks some clout Trebor Shame there isn't the same effort put into taking the incapable off the road as there is collecting speed revenue.

Hope the insurance do the decent thing quickly and you can get a suitable replacement sorted.

Any likelihood of the culprit being caught ?

Rick

[Laird Scooby]

Originally Posted by trebor

Major bad news: my Volvo was hit by a drunk driver and is now a complete write-off! :'(





Luckily nobody was hurt.

So my 10+ years of being a Volvo 940 owner have come to an abrupt end. Probably I'll be on the lookout for another one soon...

Only ONE drunk driver? How did he manage to trash both ends and both sides?

As has already been said, the important thing is nobody was hurt and hopefully the insurance will pay up and look big quickly but don't take a Mickey Mouse settlement! Try replacing a 940 for what you paid for yours 10 years ago and i think you'll need to add more money!

[Ian21401]

Condolences trebor. Ditto to the previous posts. Good luck with finding a replacement.