Like anything else there is nothing generically wrong with the MGB electrics
if they are properly maintained, yours are 25 years old after all. And it
has been covered many times.
Having said that the design of the turn flasher used at the time makes it
susceptible to low voltage or bad connections anywhere in the circuit and
that is what you probably have. More recent turn flashers work on a
different, electronic, principle and don't suffer from the problem to the
same degree. However both types have a 'fail-safe' mode if one of the
flasher bulbs fails and this is essential. On the MGB if one bulb is out
they stop flashing that side and the remaining bulb glows, on the later type
they flash at double-speed. However I have known people not notice that.
Some after-market flashers, and hazard flashers, don't have that fail-safe
mode and should not be used for turn flashers even though they do not suffer
from the low voltage/bad connection problem.
But back to your problem. If it happens both sides it is probably a bad
connection in a common part of the circuit, which could be anywhere in the
brown - ignition relay - white/brown - fusebox - green - hazard switch -
green - turn flasher - light-green/brown - turn switch circuit, or for a
rubber bumper in the common ground for the front lights although in this
case having the headlights on would probably stop them altogether.
Alternatively it could be two faults one each side like incorrect rated
bulbs or bad connections in the remainder of the circuit (you can see why
people are tempted to fit an unsafe flasher unit).
The fusebox is a common place for bad connections, particularly if putting
the brake lights on stops them flashing. But really you need to measure the
voltage through the circuit given above, with the turn switch on at idle,
looking for any sudden voltage drops between adjacent points. That
indicates a bad connection. Bear in mind you may have several.
Some fit one of the later flasher units which don't suffer from the problem,
these have three connections instead of the original two, the third is just
a ground connection so easily resolved. But personally I prefer to fix the
real problem, which is only going to get worse as time goes by.
PaulH.
----- Original Message -----
From: "electrical" <shop@ferndownelectrical.ath.cx>
To: <mgs@autox.team.net>
Sent: Wednesday, April 28, 2004 11:13 AM
Subject: MGB Electrics........
> I've been following the list for a while now and one question that I
> don't think has been addressed is the general "weakness" of the
> electrical system...
>
> I have a '78 MGB Roadster V8 Conversion and the electrics, particularly
> lights, gauges and indicator.... When I'm at the lights the indicators
> come to a stop.... When I rev a little they start up again... Is this a
> general problem of the car or just mine? How can I solve it?
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