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Discussion Starter · #1 ·
Hi Guys,

Please help. Ive installed a aftermarket MP gauge cluster on my 1965 fastback. All seems good, untill I try to switch the gauge cluster lights on. When I turn the headlight switch knob to switch the cluster lights on, all my gauge's needles goes to zero. I have lights then, but no readings. Except the speedo which does not operate electrically.

If anyone can point me in some sort of direction to solve this it will be awesome!

Another quick question. Will it make a difference if the gauge cluster shares a grounding spot with something else?
 

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Not familiar with that cluster...have a link? It sounds like a grounding issue though, are all the gauges being grounded through one wire? Do you have a picture of the wiring diagram?
 

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I'd follow up with the manufacturer.

It sounds like the light switch is removing a ground. Gauges typically spike when they're grounded.

Sharing a ground spot is not a problem. Make sure the body ground metal is clean and effective (no resistance).
 

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Discussion Starter · #5 ·

These are the gauges. They where in a box brand new that I got with the car, so not my choise. However, they look really nice with a bezel that fits. So no diagrams or any other helping tools. All off them share a common ground as you can see on the back of the gauges in the link. Fairly stait forward. The sensors ground where they attach as per normal.

These gauges are Autogauge gauges with a extra stamp, so nothing special. If someone can help me with what they know about auto gauge gauges and how they connect to the light switch, it will be awesome. And not so much the gauges, but how the connection between the gauges and the head light switch "talk" to each other as this is where the "problem" lies. Not with the gauges.

There is no "backup" from the guy who put this together, so hoping some of the very knowledgeable guys here can point me in the right direction
 

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I can't speak to Autogauge wiring. I can speak to aftermarket gauge wiring in general. The lighting comes from a single terminal on the headlight switch that provides power to the lighting circuit(most aftermarket guages have a white wire to provide 12v+ to the light bulbs, the black wire from the bulbs runs to ground, your bulb wiring color may be different). That is it for the lighting circuit...headlight switch provides 12v+ and bulbs ground to chassis. This means that the only way your gauges cut out when the lighting circuit activates is if you have a bad ground....always assuming that the lighting circuit on those gauges is strictly just bulbs, which it looks to be. I would run one ground for the lighting circuit and a different ground for any other grounds that the cluster uses(good clean grounds both) that "should" solve any issues unless you are taking 12v+ from the headlght switch for any other cluster function that is not lighting
 

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I experienced erratic gauge movement to all my Autometer gauges moving to max momentarily. This was caused by a black ground wire coming apart within the wire bundle. I found the loose or semi touching black wires. But I am not sure what would cause all your gauges swinging to the low gauge position.

I assume you have only one black the wire going to a good chassis ground. Insure wires to cluster lights are not crossed (+ and -). Do the cluster lights even come ON? I would get back to the basics and start checking voltages and ohming out the ground wire to chassis. If doubting, test the voltage out of your light switch + wire. Tough working to T/S another's wiring installation.


What to Do When the Gauges in Your Car Aren't Working

What If the Gauges Seem Erratic or the Needles Are Pegged?
When the gauges move erratically or are pegged at the highest possible reading, the problem is usually a bad component like an instrument voltage regulator or a bad ground.

Erratic gauges, or ones that seem to read uniformly low, are usually caused by a bad instrument voltage regulator. In some cases, you may be able to remove the regulator, clean the connector terminals, and reinstall it.

Gauges that all read full all the time are usually caused by a loose or bad ground. If you can locate the ground, either visually or with the help of a wiring diagram, you’ll want to make sure that it is secured tightly and free of rust or corrosion.
 
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