• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

MGB Electric problem '75 MGB

Share this page

C

ceedub

Senior Member
Country flag
Offline
I have a small wiring problem with my "B". When I turn on the headlight switch, the tachometer quits. All lights are working OK. I suspect that it is a ground problem, but I am not sure where to look for a solution.
 
Yours is the last tach type produced and is on cars from '74 on. It has a 12v connection and an input connection that goes to the negative side of the coil. It is grounded through the case of the tach. Look here: https://www.mgcars.org.uk/electrical/last_tach.html You might have a loose connection at the tach or where it connects and, when the lights go on, the bulb in the tach loads the circuit down so the tach wont work. The tach connects directly to 12volts and doesn't connect to the regulator because the regulator pulses and would effect the tach reading.

Bob
 
Back
Top