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MG MGB Technical - What circuit controls gauges?

Morning All,
The fuel, tach, temp gauges on my '72 stopped working when they had been previously.
Obviously something has gotten disconncted to affect all gauges at once, however I cannot find the culprit.

Any ideas?

Thanks in advance!
Dave
David Steverson

Dave, all electrical gauges have a green wire with 12 volts feeding them. It usually comes off the green connector at the input to the voltage stabiliser. They also all have a ground wire, I don't recall the if the ground has a connector between the gauges and the under dash wiring harness.

Clifton
Clifton Gordon

Dave,

As Clifton says, the green wire feeds the instruments, although the voltage stabilizer feeds the temperature and fuel qty instruments via a light green wire (sorry, my mgb manual is at work, but I believe it may also have a dark green stripe). Since all three are out, I would check for panel lights which would tend to verify the ground, and then check for continuity in the green circuit from the fuse block on, and then check the output of the voltage stabilizer. The darn stabilizer is located high on the aft side of the bulkhead between the passenger compartment and the engine compartment. It is easiest to reach if you remove the driver's seat and lay on the floor, unless you are a contortionist.

The tachometer should continue to work with the voltage stabilzer faulty, since the voltage stablizer doesn't feed the tachometer, so a connection before the stabilizer would be a more likely fault. Wires usually are fine, but connections fail.

The Moss catalog has a pretty good chart in it for wire colors which I believe John Twist wrote, and with a manual, a test lamp and a multimeter you can do a lot of trouble shooting, if you follow the wires from fuse block to their end, as long as your fuse block is making good continuity. But I always check grounds first.

dave
Dave Braun

But before you start messing with your test meter, just check the third fuse down in the fuse block, it feeds those three instruments and the blinkers and wipers.
The Wiz

This thread was discussed on 30/04/2006

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