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MG MGB Technical - tinkers and brakes

Have a 1974 MGB (chrome bumpers); have had it since
1984. Current issue is very perplexing.

the 'tinkers' quit working when brake pedal is depressed. also, depressing brake pedal places a 'load' on generator, causing red alternator light on instrument panel to glow dimly. And if lights are on, and brake pedal is depressed, the bulb used for both
lights and brake does not get any brighter. i.e. cannot 'see' brake light when lights are on.

Anybody seen this before????????????????

While chasing this issue using the wiring diagram from the Hayes manual, came across a 'voltage instrument stabilizer'. Anybody know where this is physically located on the car???????

THANX!!!!!!!!


L Rousselle

Two things come to mind. You could have a ground fault in the brake light circuit. E-mail me at SUfuelpumps@donobi.net and I'll send you a reprint of an explanation about this phenomenon by Rick Astley, author of MGB Electrical Systems. The other possibility is the brake light wire going into one of the sockets has been pressed over by something against the socket stored in the fender well of the trunk and grounding out. I had this happen to me on a trip in our MGB and I made up some protective covers to go over the back of the sockets to prevent this from happening. Cheers - Dave
David DuBois

Yep. It sounds like a shorted wire in the braking light system. Dave's recommendation to check in the trunk first will likely turn up the culprit. RAY
rjm RAY

A short in the brake light circuit would be expected to blow the green circuit fuse, unless the fuse has a bad connection which limits the current below that at which it would blow. In which case the simple load of the brake lights, without a short, will stop the flashers (never heard them called 'tinkers' before, you can get arrested in the UK for using that word ...) flashing.

Whilst a bad connection at a rear light cluster will cause odd effects including stopping the flashers flashing when you try to use two or more of the running, brake and indicator lights, because the rear light clusters are earthed through their physical fixings to the body you would need both sides to be bad to affect the flashers both sides.

If the flashers both sides are affected then a bad connection at or near the green circuit fuse is the most likely single cause. But you could have more than one or more fault, of course.
Paul Hunt 2010

Found the 'short'.........in the right brake light
wiring.

Can't say enough about this bulletin board. haven't used it in a while......but sure glad it is here!
L Rousselle

Yes neither flashers nor tinkers are deemed to be politically correct it would be said.
Iain MacKintosh

You still must have a bad connection, as that is the only think that can cause the voltage to drop under an excessive load. Because it was also causing the ignition warning light to come on it must be in the ignition switch or back from there towards the starter solenoid.
Paul Hunt 2010

This thread was discussed between 02/04/2010 and 05/04/2010

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