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Discussion Starter · #1 ·
I am redoing a 69. The dash harness is fine but I am not getting any power to the small 4 amp fuse on the fuse block, and the lights in the dash clock don't work, even thought there is power to the clock and the map light has power. Looking at the wiring diagrams, I see that all of the interior lights; radio light, clock lights, etc, are powered by the blue/red stripe wire, which doesn't have power and feeds from the 4 amp fuse. Does the headlight switch feed power to the 4 amp fuse when the lights are turned on? There is no continuity across the fuse, whether the headlight switch is on or off. I'm thinking it could the switch. Any knowledge of this situation?
 

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Did you turn the headlight switch all the way to turn on the dash lights? It may have gotten turned low/off?

Radio light gets its light from the triple female accessory plug behind the dash. I think its red.

Supposedly the headlight switches go bad after a while from internal corrosion. For my money I would chuck a new one in there as I am about to myself. They are quite complicated and all the wiring for the lights run through there.

I would first remove the fuse block and test the contacts on the back. Be nice to know the condition on the backside. It's only two screws and then you know.

Peter
 

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If there is no continuity across the fuse, why are you looking anywhere else until that issue is taken care of?

Or, do you mean there is no voltage on either side of the fuse? That does not necessarily mean there is no continuity across the fuse.

Terms of reference are important in electrical work. Please be sure you are using the correct ones.

You are correct in that circuit 19 (light blue with red tracer) powers the instrument lights. Circuit 19 runs from the headlight switch (terminal I) to the fuse block, through the 4 amp fuse, and on to the lights.

Possible problems in the switch could be a faulty dimmer resistor. If your tail lights function OK, then I would suspect the dimmer resistor.

Let us know what you find.
 
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If there is no continuity across the fuse, why are you looking anywhere else until that issue is taken care of?

Or, do you mean there is no voltage on either side of the fuse? That does not necessarily mean there is no continuity across the fuse.

Terms of reference are important in electrical work. Please be sure you are using the correct ones.

You are correct in that circuit 19 (light blue with red tracer) powers the instrument lights. Circuit 19 runs from the headlight switch (terminal I) to the fuse block, through the 4 amp fuse, and on to the lights.

Possible problems in the switch could be a faulty dimmer resistor. If your tail lights function OK, then I would suspect the dimmer resistor.

Let us know what you find.
I vote for the dimmer resistor. This is a common problem. But as was said above . . are you not getting continuity or do you mean current across that fuse??
 

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Discussion Starter · #5 · (Edited)
I vote for the dimmer resistor. This is a common problem. But as was said above . . are you not getting continuity or do you mean current across that fuse??
The headlights, tail lights, marker lights, map light, shifter light, courtesy lights all work. Power to the clock and map light but no power to the clock bulbs, heat switch illumination, and internal radio light (there is power to the radio). They are are the same circuit 19 (blue/red stripe). No voltage across the 4 amp fuse, which powers the circuit. Looks like it runs thru the headlight switch first. My guess is the switch. I tried continuity tests across the switch terminals. yes to the headlights, no to the dome lights or accessories. Can I check continuity that way? by junmping the terminals to check it? I have other switches and checked one other. Same problem.
I pulled the fuse block and checked it. Looks good. But I suspect that the power across the 4 amp circuit is activated by the headlight switch, and with the fuse block out, I can't check that.
 

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Discussion Starter · #6 ·
bump
 

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Do you have gauge illumination? If not, you probably have a dirty or defective rheostat at the front of the headlamp switch. Sometimes these can be cleaned (clean the copper contacts with a pencil eraser). If that doesn't work then replace the switch. If you have dash illumination but no clock, heater control or radio illumination, it sounds like an extension harness has become disconnected. IIRC, on many of the cars I've seen, the dash illumination terminates with a 3-gang female bullet connector and additional lighting gets plugged in as needed, eg. console, radio, clock, etc.
 

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I have seen many fuse blocks completely corroded on the back. I just replaced one that was beyond help. Before I replaced it, I had a lot of strange problems. NPD sells the fuse box connections if yours need replaced.
+1 for headlamp switch also. I have replaced a few of these also.
Keep us posted on the fix, it could help the next person that has this problem.
 

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Discussion Starter · #9 ·
I have seen many fuse blocks completely corroded on the back. I just replaced one that was beyond help. Before I replaced it, I had a lot of strange problems. NPD sells the fuse box connections if yours need replaced.
+1 for headlamp switch also. I have replaced a few of these also.
Keep us posted on the fix, it could help the next person that has this problem.
Its not the fuse block. It is in pristine condition. I can't check the gauge lights because the gauges aren't in the car. I want to get all electric correct while I have the access to the wires behind the gauges. Besides, I want to test the gauge connection before it goes in, being a tach cluster. Guess I'll try to locate a good headlight switch and try that. Unfortunately, I didn't get any answers on how to check the switch and if circuit 19 is activated by the switch being pulled into the headlight on position. Looking at the schematic, it shows the power going to the switch, then going to one side of the 4 amp fuse then going to the illumination. I'm figuring there isn't any power to the 4 amp fuse until it is power from the switch. Maybe the 4 amp fuse is there to protect the switch in the event of a short.
 
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