Meter lamp problem

[jray1942]

I'm having a problem with my dash light circuit on my 1975 280Z. When ever any lights are turned on the 20amp fuse for the Lighting/dash lights burns out. All the running lights will work if I disconnect the dimmer resistor.

Using the FSM ( Page BE22)I have done the following steps:

Checked all lamps in circuit (Running lights as well as dash lights) for corrosion and have checked that all lamps are good by pulling out all gauges and testing them with an outside 12 volt source.

Checked the dimmer control and registers good with 10 ohms at full resistance.

Have checked the fuse block front and rear. All good.

I have disconnected all the instruments from the instrument harness and completely isolated the circuit by disconnecting C-2,C-4, C-6, and combo switch.

All 5 instruments are unplugged from harness. That would indicate that there is no connection with the Green/white power line. It measures dead short to body ground!

2 questions: Can this line possibly connected to some other part of another circuit that could result in this ground short, or, is this line shorted to ground somewhere in the harness trough under the dash?

The wiring in this vehicle is in pretty good shape even after 34 years (Vehicle has been setting for the last 10) and I have not found any burnt or scored connections. I have also cleaned all body/engine/and starter connections.

My next step will be to take off the dash to gain total access to the harness unless someone with better knowledge can help me.

[EScanlon]

What was the LAST thing you had done/ did before this problem started happening?

Start there, your answer may be as simple as a reversed wire.

E

[jray1942]

Not that easy. I just obtained this car for restoration. This issue bugged the previous owner and was one of the reasons I got it 'cheap'. He had jerked out the dimmer control thinking it was bad but it isn't an issue as it only effects the current in the lamp. I have reversed the wire to the dimmer just in case he had done that very thing but it should'nt matter as the only effect is to reverse the direction of illumination control. I'm going to lift the body ground wire today to see if that has any effect on my short with the G/W wire to see if I'm getting a false reading. Additional, When I check the power side (12v) at the fuse without the light switch I get about 50 ohms which is about right. When the lite switch is placed in either park or headlights, this same point shorts to ground. Thanks for any help, and I will again check for reversed connections which the previous owner may well have done.