I was driving last night and my dash started smoking from the headlight switch area. I parked the car and disconnected the battery and haven't had a chance to take a look at the car yet. Can a headlight switch smoke? I'm hoping I can just change the switch and the problem is solved. Thanks

 

I would guess that you are looking at a bag dimmer switch. They get hot, and sometimes fail... and I would think smoking would be a symptom of such. And it is just above the headlight switch. It is relatively easy to pull out-pry off the molding and then the two screws that hold the instrument cluster in place, so you can get off that metal soupport bracket. Then, I turn ring comes off and you can get the dimmer sw off. If you see burn marks, there's your culprit. Btw, what year is your 240?

 

Thanks for the advice. I took a look at the car and pulled the instrument cluster and my dash lights don't work. Nothing was smoking or smelt burnt. I guess my dimmer switch went bad. Another problem that I realized is on really cold days my headlights don't work until the car warms up. Does that mean my headlight switch is going too?

 

the headlights are on relays which are up front. do the highbeams work when its cold? they are on a separate relay. if both are bad, then its more likely the headlight switch, or something in the wiring harness.

ya know, you didn't mention what year/model car this is... 240-740-940 encompases 20+ years of engineering changes and 3 base models.

 

Sorry it's a 1991 240 wagon. The high beams work when my headlights don't. I drive with the high beams on until the car warms up and then my low beams work. It only does this on extremely cold days.

 

then I'd check the 'step relay' up front. its a rectangular relay with 2 3-pin "T" shaped connectors on it. everything before that is common to the highs and lows. the lowbeams are on the grey wire from pin 56B of the step relay, this is wired to the bulb-out-detector which is behind the dashboard, then separate blue wires to the two low beams.

and, yes, I suppose it COULD be the bulb-out detector. this is basically pairs of counter-wound coils around a magnetic reed switch. if the current is the same in the two coils (left and right low beam), then there's no magnetic field, so the reed stays open, and no bulb-out idiot light.

 

You're awesome Pierce. Thank you guys

 

The only other thing I might check is to make sure where your headlights ground is making good solid contact. I have solved a few strange electrical issues by cleaning my grounds.

 

My new(used) dimmer switch went bad already. Why am I burning out dimmer switches?

 

something is drawing too much current, maybe a short circuit.

 

The only thing I changed was my instrument cluster with another year cluster..could that have caused any problems. Electrical is not my area of expertise. I dont even know where to begin.

 

how different of a year? I'd have to compare the wiring diagrams of the two years to see whats what.

there's lots of things you can do wrong... hooking up the red-white tachometer wire on a car that doesn't have a tachometer will fry stuff.

 

I learned about the tach wire the hard way, I fried my last cluster. The new cluster didnt have ABS and something else im forgetting, but everything worked fine. Its been in for about 3 months and I didnt have a prob with the dimmer until last month. The only other problem im having is on very cold days I lose my headlights until the car warms up, not sure if that has anything to do with the dimmer?

 

the headlights have nothing to do with the dimmer.

but it does sound like there are some bad connections....

 

re: high/low beams


Soo... probably a bad connection between your hi/lo switch (C) and the step relay (A). I'd check and clean those connections. headlight relay (G) is probably not your problem, as I think that just cuts on and off the headlights. Also, step relay could be the problem itself. It is on the drivers side fender under the hood. If you can't find it, when it is warm enough to fuction, leave the car off, and have someone flick on and off the high-beams--and you will be able to find the clicking relay.

As to the cluster... find out what year the cluster came from. If it is not a '91, that could be your dimmer problem. Seems likely to me, actually.

 

great wiring diagram. Where did you get that? Can I find one for my 2000 c70 coupe.

...m

 

thats from the volvo "Green Books" (one for every year and model car). not sure they drew these for anything much newer than the mid 90s.

 

This particular wiring diagram came from OTP (Original Technical Publications) which are just official scans of the Volvo greenbooks (and not always the greatest of quality). I haven't seen them for anything newer than their 850s... your next bet would be contacting volvo to get the diagrams from them... but I've also heard of people subscribing to things like "all data" that for a monthly fee give you access to all the information relevant to your car. I've heard good things about them, but don't use it myself.