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Discussion Starter #1
This past winter, I took my dash apart to replace my heater fan and introduced some problems on the instrument readings which have progressively gotten worse.

1) Intermittent tachometer (pegged counter-clockwise vs. accurate reading)
2) Brake and temperature warning lights go on and off together intermittently whenever I hit a bump in the road
3) Heater fan light does not work

While I had my dash apart, I replaced all the instrument lights with LEDs and verified they worked before reassembly.

When I bang on the dash, the brake and temperature lights flicker on and off.

Based on papajam's wiring diagram, I verified a good connection to connector A (brown) in the monopod, which controls the brake and temperature lights as well as the fan light (but not the tachometer). I also cleaned the battery terminals to ensure a good connection.

Any suggestions on where to look for the problem?
 

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I would take the instrument panel out and have a look at the connectors on the back of it. The thin copper strips from the flexible printed circuit board that make the male connection for the female plugs can come adrift. They then don't make good contact or can touch each other and cause a short. Somewhere you have bad contacts and my guess would be there.

The tachometer is held in place by three little nuts. These also make the electrical contacts and they can shake loose.

You don't have to take the dash apart. Take off the plastic surround from the monopod, its not as flimsy as it might seem and is held in by lock tabs at the top and sides, then take out four screws to pull the instrument panel towards you. Detach the four plugs at the back, making sure you release the tabs that hold them in place, and you can lift the whole thing out and check it over.
 

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Discussion Starter #3
I found the problem with the temperature and brake lights. I forgot to connect one of the ground wires to the frame when I reattached the dash.

Thanks for the tip on removing the instrument panel. I was able to replace the heater blower light in about 30 minutes.
 

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That printed circuit sheep is always the source of problems, especially after it has been fooled around with. Anyone getting inside one of the monopods instrument heads needs to examine the circuit sheet carefuly for cracks. When a crack occurs across the circuit, vibartion and heat expansion can cause various intermittent problems. Finding a good used instrument housing is the easiest solution if you have a cracked printed circuit, providing it has a good sheet. There are probably places who can do a micro jump repair of a cracked sheet, but I don't know where you would find such a technician. Someone who repairs old sterio equipment might be able to do such repairs, as well as those shops who specialize in Auto Instrument repair.

Robert
 
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