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MG MGB Technical - Where is dash electrical ground

I had a surprising (or not so surprising) problem on my way home from work today in my 1972 mgb roadster (all stock). I got stuck in a line of slowly moving traffic for about 15 minutes. I kept checking my temp guage as the needle moved up just past the "N".

When the traffic cleared and I got up to speed, I again checked my temp guage only to see it resting all the way to the left on cold. A quick check of my other dash guages showed that all of the electrical guages were not functioning (fuel, tach), and the turn signal indicator lights did not work (they do come on with the emergency flashers). The headlights work on both high and low beam. The ignition light works.

Are all of the guages and the turn signal indicators tied to a single ground? Is it in a standard location generally across all years of MGB? Where is it and how accessable is it?

Thanks for your help in advance.
glq Greg

The system ground is for other circuits as well as the circuits you mention. All the items you mention as not working are fed by green wires from the fuse box. Check the third fuse down, if good the fuse holder cantacts may need cleaning. Do you have a test light or a meter to determine if voltage is present on the green wires?

Clifton Gordon

Hmmm. Clifton, I was sure it was a ground.

The fuse was not blown, but in order to pin it down to just corroded contacts, I turned on the ignition to check the brake and back-up lights. They did not work either. Proof enough. I cleaned the fuse contacts, and the wiring harness contacts to the third fuse, and now everything works!

Thanks for your suggestion and quick response. It looks like I will get to drive the B to work again tomorrow!

Safety Fast!


glq Greg

glg Greg: Just went through the same /similar incident with my 79 MGB. I had lost all dashboard gauges except the oil (as it is engine driven) heater fan, w/wipers, directionals, and brake lights.

I did the following:

Removed and replaced ALL fuses and terminal ends

Super-cleaned ALL contact surfaces both internal and externally of the fuse box including the two inline fuses below the fuse box. Super-cleaned the terminals at the starter relays and replaced terminal ends

Everything is now working properly

Let us know how your item turns out


Gary :>{D
79 mgb

This thread was discussed between 02/07/2008 and 07/07/2008

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