MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Tachometer gone haywire

After setting idle for several months, my 72 B's (US Spec) tachometer needle would shoot all the way over to 7000 RPM when the key was turned to the on position (just prior to ignition). After starting it would hover between 6000-7000 RPM, almost acting as some sort of voltmeter. I checked all the conections on the tach and replaced the voltage stabilizer (located under the dash) to no avail. This was apparently the first mobel year to use impulse rather than mechanically driven tachometers. Is this repairable or is a trip to the junkyard in order?
William

I had that happen on a 240Z and it was the tach. After replacing it all was fine.
Mike MaGee

The voltage stabiliser is nothing to do with it, that just controls the electric temp and fuel gauges, and the electric oil gauge in 68 only. The mechanical tach finished in 64 when it was replaced by the current-operated tach, 72 was the last year for that tach, replaced for the 73 year by the voltage operated tach. Possibly the points are 'fizzing' instead of making a clean contact. Disconnect the white from the coil +ve and if it still does it then it is the tach itself or possibly the 12v and ground supply to it, otherwise it is the points or some other bad connection in the ignition LT circuit.
Paul Hunt

This thread was discussed on 02/01/2004

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.