1972 "U" code

I just purchased a 72 supreme and noticed that with key on and when running
That marker lights are on and if I turn dimmer switch front blinker also get
Brighter. Bad ground or headlight switch??
Don't think I should have any markers until
Headlight switch pulled out. Just ordered chassis manual

Any help appreciated Dave

joe_padavano

The side markers will flash with the turn signals, so if there's a problem with the turn signal switch, that might cause them to come on with the key, but so would your turn signal lights. In any case, there is no connection between the dimmer rheostat and the park lights or turn signal circuits. The only place those circuits are even close is in the headlight switch, so either someone has mucked with the wiring or the headlight switch has an uncommon failure.

1972 "U" code

Thanks for the info. It is strange. If I turn the headlight switch in the dash clockwise the 2 lamps in
The bumper get brighter. If it turn it counter clockwise until just before dome lights
Kick on it's dull glow you can see from the bulbs. The marker lights I thought would only
Go on when it is pulled out to first position or when headlights are on I position 2. Going to double check chassis ground later

Octania

Dash pods should have a ground strap to each pod I believe.


bare braided wire at aft end of RH head to firewall


Battery (-) post 10g or so to radiator support


Headlight sw also presumably has a gnd strap in order to activate the courtesy lites


CSM will have a color wiring diagram.

MDchanic

The problem that you have is a problem that is impossible.

This means that the wiring of your car has been modified in some way, whether intentionally, or by accident (such as melted insulation in a harness).

- Eric

joe_padavano

^^^This. As I noted above, this is not the usual bad-ground-for-the-1157-bulb problem. I've actually had a lighting issue that ended up being an overheated connector and melted wiring at the headlight switch. It was an 86 Chevy truck, but that's pretty much the same switch.

1972 "U" code

I have removed aftermarket tach and all radio wires as they were all over.also wanted
Factory tach to run instead. Fuses checked,ground to radiator support cleaned.
Now ready to start over.waiting on chassis manual. Only other wires are for msd ign
Ant tach adaptor. Ground to radiator support,white to msd box,red to power,purple to
Brown tach wire.
Regarding side marker lights and front blinker lights they are on faintly but will adjust
With intensity when turning dimmer on headlight switch.havea new ac delcoone ordered
Any other ideas appreciated thanks Dave

MDchanic

Other ideas? Get in there and find out where the short is. Two conductors are touching which should not be, likely a grey and a brown.

First places to look are the headlight switch plug and any point in the dashboard harness that contains the heavy orange wire to the cigarette lighter, which tends to short to ground, overheat, and melt, creating odd cross-connections inside the harness.

- Eric