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MG MGB Technical - Indicators causing chaos

I wonder if anyone can assist please.

I have a 1978 mgb roadster. Very frequently (but not all the time) when I use the indicators they will not work and stop the heater working and the tachometer. This happens whether the engine is running or not (engine is not affected) and if I turn the ignition off and on everything starts working again (until the next time!). I understand that all these run off the same power and its probably a bad connection somewhere, but would appreciate any guidance as to how I can track the problem down. Thanks.
D Callaghan

check the fuse box, remove fuses and clean contacts, also check your earths,
mike
m j slater

Don't bother with earths, there aren't any in the indicators except right out at the lamps, and if they are bad they will cause non-flashing of the indicators rather than failure of other circuits. The rest is good advice, what is probably happening is that the extra current drawn by the indicators is causing a bad connection in the 12v supply to fail altogether, and as it is affecting things like the heater and the tach it almost certainly is to do with the fusebox, specifically the 2nd fuse up white to green. As well as the fuse to holder connections and spade connections there is also a riveted connection on the back between the spades and the fuseholder. Whilst the first two are cleanable if the third is the problem get a new fusebox, which if it looks pretty manky I'd do anyway.
Paul Hunt

Does the problem occur on both sides or just one side? If it only occurs on one side, you could have something in the boot that is pushing against the wire for that rear indicator against the outside of the socket and causing a short. This happened in our MGB several years ago when a camera case I was carrying pressed hard against the wires. I have since made covers for the back of the sockets that has eliminated the problem permanently. See the article, Tail Light Protective Cover in the Other Tech Articles on my web site at: http://homepages.donobi.net/sufuelpumps/ Cheers - Dave
David DuBois

That *should* have blown the fuse, if it doesn't it indicates (ho ho) there are bad connections back through the indicator circuit and fusebox as well, which will be cause slow flashing when the other circuits *are* working!
Paul Hunt

This thread was discussed between 21/03/2009 and 23/03/2009

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