Fuel and Temp gauge

[72valiant]

These two gauges are driving me nuts! For about 10 years the temp and fuel gauge on my '72 Valiant have not worked. I'm not a skilled mechanic by any means but I've attempted to fix them every now and again with advice from people on this forum and people I know. I've replaced the gauges, replaced the cluster voltage regulator, tested the blue wire with the white tracer. Nothing has fixed it.

Then all of a sudden last night for no apparent reason both gauges show signs of life and start moving! They both seems to be off with their accuracy. I have a full tank but the fuel gauge only went up to a quarter of a tank. Does any one know why these gauges would spring to life? I had replaced the brake light and dome light fuse a few days ago but that's it. I'm excited that they are showing signs of life but I'd like to know why and maybe then be able to make them show an accurate reading.

 

[mderoy340]

Check the Voltage regulator connection. There are 3 spads, 12V feed, 5V output, GND. I always add a ground wire to the instrument cluster case. The mount screws provide a ground when tightened to the dash.

 

[RedFish]

The spade connectors on the limiter are very substantial by comparison because they support the weight of the limiter. The female connectors used are only snapped in so they absorb or dissipate vibration/shock. A loose connection here, due to age and/or corrosion has been the fault found.
Some have added gobs of solder where these females terminals meet the circuit board. I don't know if that's a good plan.
If you buy a solids state regulator with ring terminals, a #6 X 3/8 screw with toothed washer can be used to make a secure connection in those female connectors.

 

[72valiant]

I was testing the rest of my fuses with a test light today. The last fuse labeled Instruments doesn't seem to be getting any power. The test light didn't light up when connected to either side of the fuse. I replaced the fuse and got the same result. Does this fuse control the gauges or the limiter and if so why would no power be going to the fuse?

 

[RedFish]

that fuse is illumination. Gets power when headlight switch is pulled to park lamp position.
At some year model the gauge limiter supply was routed through a fuse. I forget what year.