MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

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 Issues

My tachometer on my '66 MGB does not work. Not at all. Not a flicker from the needle and no light. The earth is good, the power supply is good, the cable from the coil to the ignition is good. Is there anything else I can test? I am not into dismantling it unless someone convinces me it is straightforward and anyway I can't even turn the bezel, but if I buy a new (reconditioned) one, can I be sure that it will work?
D E Wheeler

if the light doesn't work and the power to the bulb is defo there then your earth is bad. If the earth is in fact bad the taco will not work.
Fix the light and try again before going any further.

MGmike
M McAndrew

Hi,

Has the car been converted to negative earth? If so then maybe the tacho wasn't and probably is toast. Also, even if it has been converted the wire loop through the sensor needs to be the opposite way to that shown in the manuals.

Repairing is fairly easy, if you have a smidgin of electronics knowledge. See

http://www.sunbeamalpine.org/downloads/alpine_tach_repair_rev5.pdf

Getting the bezel off, after removing the tacho from the dash, can be achieved by gently bending the tabs up a bit and then carefully twisting, prising the bezel.

Herb

Herb Adler

Thanks for your replies guys.
Mike, following your suggestion, I had a clean-up on the bulb connections and now the light works - a step forward - but still no movement on the needle.
Herb, no it is still the original positive earth. I did look at the site you recommended and am vaguely tempted, but not convinced that I have the know-how to start rewiring it.
Any other ideas much welcomed.
David
D E Wheeler

David,
if the car runs okay the tacho should be seeing the pulses via the pickup, both the supply and earth are okay then the only thing left is the innards.
If you're not confident to strip and refurbish it yourself you really only have two options. 1, buy a new/refurbished one with a guarantee or 2, try your luck with a second hand unit from that well know auction site ;0)

MGmike
M McAndrew

I have noticed that the ignition/coil cable is damaged near the coil, where chewed by a mouse! The connection is obviously still there or else the car wouldn't start but could that be enough to stop the tach?
David
D E Wheeler

Maybe that damage is allowing the sensing loop to short out. This would still allow power to the coil, but would bypass the tacho sensor.

Herb
Herb Adler

This thread was discussed between 05/08/2012 and 08/08/2012

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now