Have an interesting one for you guys. Having some issues with my interior lights/gages and my driver side door jamb switch.

If i have my driver side door open (or ground out the white wire for interior lights), and turn my dimmer **** all the way counter-clockwise, my gages and cluster lights work fine, voltage reading right around 14V. However, if I turn the **** off the detent, the voltage gage drops to 8V, and my temp gage slowly climbs. If the white wire isn't grounded (door closed), the gages get real goofy - voltage gage drops completely, and high beam indicator and turn signal indicators turn on. Any ideas on specifics to check before I dig into the interior light circuit completely?

 

Bump - anyone have any thoughts or good pointers on where to start, if there may be an odd ground crossed somewhere?

I'd also replaced the headlight switch when I noticed this, because of how it changed a bit with turning of the **** and turning on the lights

 

Check your circuit board behind the gauge cluster for corrosion or cracks, reproductions are available. Locate and clean all interior grounds.

 

Agree w Komet. Clearly a ground problem. Having the interior light current pass through the same ground as the cluster, which is what happens when you use the dimmer to turn them on, is what's going wrong. Probably not a problem with the cluster itself; more likely, the wire in its harness that grounds it, is also grounded at the same spot as the one from the HL sw, and that connection to the chassis is corroded or loose.

 

Thanks guys. That makes sense now Sofa; so basically the thought is that the ground for the circuit is bad; and basically because I grounded the dome light circuit 100% of the time, when I override with the dimmer switch, it completes the ground for the gages that way. Correct?

All the other gages seem to work correctly the entire time, besides voltage gage and an aftermarket temp gage, but saying that is it possible the PO's wiring of the gage may be contributing to the issue?

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The interior lights all have 12V on one side full-time (orange wire); then to turn them on, the door switches, or the dimmer switch, ground the other side (white wire), to complete the circuit. Which means then, that there is ZERO interior light current flowing in the dimmer sw ground connection most of the time, but when you turn the lights on that way, then there IS current in that wire. If the dash is grounded at the same spot (let's say, a screw at the firewall, or some dash bracket, or something), and THAT connection is bad, then when the interior light current starts to ALSO flow through that bad connection, the ground wires will NO LONGER be at ground. They will be at SOME OTHER VOLTAGE that will depend on the resistance of the bad connection (which is supposed to be zero butt now is some much higher amount) and the amount of interior light current. Then at that time, the terminals of all the gauge circuits that depend on being grounded, will instead have 3 volts or 7 volts or 9 volts or whatever, instead of ZERO volts, which of course will make them all go wack.

You didn't mention anything about PO adding aftermarket gauges before. Butt, that makes it ALL THE MORE IMPORTANT to check ALL the wiring in there. You might find it's a witch with a capital B to actually DO that, even as eeeeeezzzzy as it is for me to tell you that's what you need to do; the dash was fully assembled as an assembly long before it was put into the car, with the complete wiring harness including the fuse block attached to it, and some little metal brackets on the back of it, which were then bolted into The Car proper as it rolled down the production line. Some of those brackets had grounds connected to them. Then more parts were added on top of that as it continued on down the line, making it MUCH more of a hassle to get to some of the parts of it that were put together when it was all out in the open. Now that you're revealed to us that some PO has been hacking on the wiring, it's impossible for us to guess what they half-a$$ed, or left loose, or bozhye only knows what, especially now that it's getting too dark out for us out here to see up under your dash as well as you can. WHO KNOWS what evil lurks in the heart of a pair of dykes wielded by an idiot. (hint: The Shadow knows...)

 

Well after taking a look at the PCB, it's definitely seen better days... So I'll definitely start there but still double check all ground pins to the cluster

 

Well, it's definitely better after replacing the flex board; but voltage still isn't quite right plus big fluctuation on the gage with the turn signal if I don't have the override on, so time to dig into the grounds and mess of wires


In the interim while I dread digging into the dash... Adding a strap from the ground under the driver side dash to the driver side kickpanel seems to be alleviating all issues