78Silver928

I've been trying to get my instrument lights functional on my '78. None of them light no matter where you put the rheostat. I checked number 5 fuse, found it blown... thought that was the smoking gun, but replaced it and still no power to the rheostat with headlamps on. Any ideas for where to look?

soontobered84

https://www.928gt.com/t-7879fuse.aspx

928 Specialists Fuse/relay chart for 77-79 shows fuse 4, 5, 11 and 12 all concern instrument lights. Have you checked all your fuses?

Hey_Allen

I found a loose connection on the back of my CE panel when I was chasing the cluster lights in my '78.
I ended up pulling each connection, tightening them slightly, and adding a drop of Deoxit D100 as I reinstalled them one by one.

I haven't had any cluster lighting issues since, other than a completely shot dimmer that is jumper bypassed (with a low current blade fuse...) for now.

Jason89s4

As recommended by John, check the fuses.

Also, it could just be a bad rheostat (dimmer) switch/dial. Make sure the lights are off, key is out, and you can easily remove it from underneath, it is held on by one very small phillips head screw to the bottom of the instrument pod. That switch will get very corroded over time. Sometimes you can soak it with DeOxit and work it back and forth and it will be okay. Other times it's toast.

There are two wires to the dimmer switch, which if you remove from the switch and jumper them together (thus eliminating the dimmer function), you should get full illumination at your instrument panel and A/C control unit, clock, ashtray, etc. If not, your problem is not the switch, it is a fuse or other issue on the way to the dimmer switch.

The voltage to the dimmer switch (and ultimately the illumination of the aforementioned) originates at the headlight switch. So, how's your headlight switch doing?
-Jason

78Silver928

I have checked all of the fuses, and checked the rheostat. As mentioned, number 5 fuse was blown, upon replacement, no difference. There is no voltage at either wire at the rheostat with lights on.

Hey-Allen where was the loose connection, and what is the "CE" panel? Is it accessible with the pod still in the car?

SeanR

Check your clock light and ash tray lights (if you have one) as if one of those is disconnected the pass through power to the rheostat will not have power.

Hey_Allen

The CE panel is the Central Electrical panel, or fuse and relay panel.
Before assuming a loose connection behind the panel, I found that there was no power on either side of the fuse holder for #5, and that I had dash lights when I jumpered power to fuse 5 from another fuse.
When I found that, I went ahead and pulled the panel and started checking what was going on, which resulted in finding a number of slightly loose, and oxidized connections.