MG Car Repair: Sending Unit, fuel gauge, temp gauge

Question
Hello Howard,

I am grateful that you are generous with your time. I have a 1970 MGB completely restored, but both the Fuel gauge and the Tachometer are not working at this time. Could those 2 items be electronically connected?  or  

Answer
Hi Jeff,

The fuel gauge is powered by a wire from the voltage stabilizer (10v) and if it looses power from the stabilizer, the temp gauge also must be dead. The tach wire supplies power to the stabilizer from a direct hot wire in the harness.

So to test the system just use a voltmeter or 12v test light and turn on the ignition and test the light green w/green tracer wire on the fuel gauge for 10v or a dim light of a test light. Then check the single green wire plugged into the back of the tach for full 12v. or a bright light of the test light.

You may also test the black wire on the back of the tach to see if they are grounded well.

If you don't have a wiring diagram, let me know and I will post one on my web site for you to copy.

Howard