MG Car Repair: Fuel tank sending unit, fuel tank sending unit, voltage stabilizer

Question
Hi Howard
I have a 69 mg and it looks like the sending unit or the fuel gauge is bad. Whe I started it the gauge read 1/4 tank and quickly dropped below empty. I pulled the sending unit and the float moves freely. Anyway I can troubleshoot this before I buy a new one.
Thanks

Answer
Hi Bob,
First take the colored wire off the sending unit and with the key on note that the needle deflects all the way in one direction and then ground the wire and the needle should deflect all the way in the other direction. This is a rough test of the gauge. Then check the black wire attached to the sending unit to see that it is a good ground and connect both wires up to the sending unit while it is out of the tank and keep the sending unit away from the open hole in the tank and turn the key on and hand operate the sending unit up and down and watch the gauge. You can also check the sending unit with an ohm meter set on a low ohm scale and move it up and down.
Also check your charge rate at the battery and note if any other gauge reads wrong since they are powered by a voltage stabilizer and operate on 10v not 12v. That is also why you need to check charge rate in case the charge rate is too high. It should be 13.8 to 14.5 at 1500 RPM.
Howard