Carpokes Porsche Forum

Hello Tom/All,

While I was troubleshooting dash lights, I pulled the headlight & dimmer switches off to look at connections etc. for any obvious issues. I then re-installed them.

I then started the car and the dimmer started to smoke. It started melting some plastic around the green internal component.

I purchased a new dimmer but don't want to install it until I figure out what the initial cause was for the first one to burn up.

Could someone please help me try and test/troubleshoot these connections? Please use simple terms and details due to my limited electrical background.

PS - great website Tom !!!

What was the issue with the dash lights that caused you to start troubleshooting in the first place?

I'm not an electrical engineer by a long shot, so consider the source. Melty dimmer switches are often the result of too much resistance at the connector. A corroded terminal creates resistance and heat, and with the circuit powered, the connectors just keep getting hotter and hotter as the heak soaks in and eventually starts melting stuff. That's probably the first thing I'd check. The other possiblibily is that the circuit is just flowing too much current, either because you used bulbs with too high of a wattage rating, a short, etc. You'd think the fuse would blow if first if that were the case, but not necessarily. Did you recently change bulbs? I'd be tempted to bypass the dimmer, but without testing am not sure if the circuit relies on the dimmer to keep the amps down.

Do you have a multimeter, and are you comfortable using it to check volts and resistance?

I was trying to get my dash lights to work. Read some articles that maybe the dimmer or headlight switch may have something to do with it.

After not finding any visual defects I re-installed them and that's when it started smoking.
I quickly unplugged and removed. Installed a new one and it started to start smoking.

So now I need to check the current (I'm guessing). I have multimeters & test lights and separate low voltage adjustable power source for troubleshooting. I'm also not an electrical engineer as well but can follow directions pretty good ! Setting the multimeter's dial is my challenge. Thanks!

So the dash lights are not working at all, even when you try to turn them on and before the dimmer starts smoking?

Yes, they have never worked since i owned the car. No fun at night

Do NONE of the dash lights work, or just the lights in the gauge cluster?

None - (cluster, cigarette lighter, heat/AC controls etc...)

Let me take a look at the schematic and see if I can suggest a few things to check. What year/model is the car?

I'd say you have a direct short somewhere, but you'd think a fuse would blow if that were the case -- unless the dimmer is limiting the current enough to keep it under the fuse rating.

1988 951

Ok, looking at schematic. Working backwards, do your clock, glove box light, and license plate light all work? They are switched off the same position of the light switch. So if they work, then the light switch is probably ok. Also, check fuse 38 and see if it is blown or showing any signs of going bad. It is directly in line with the dimmer switch.