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MG MGA - Electrical query - indicators

Hoping for some guidance please. My 1600 Coupe indicators are playing up. The indicators weren't working at all and the bulb on nearside rear had blown. I replaced the bulb and the indicators all worked for 2 or 3 flashes and then stopped. The nearside rear bulb had again blown and a photo is attached. Is it likely to be an issue with the indicators or perhaps a short somewhere elsewhere with the wiring? I'm not that savvy on wiring so would welcome thoughts from for forum please. Thanks. Tim


Tim Prime

Hi Tim

Was that a brand new bulb out of the packet? Looks like the vacuum has leaked from the bulb and the filament has oxidized. Try a split new bulb ensuring that it is the correct voltage and wattage.

Barry
B Bridgens

Barry. No, it wasn't new out of a box so could have been a few years old. Would one duff bulb cause all the other indicators not to work though? Tim
Tim Prime

Tim
A short won't kill a globe, that is a faulty globe, the glass bulb has probably broken it's seal in the tin bit.
If it worked for a bit with that globe before it fizzed, then all it needs is a good globe--the system relies on current draw through the globes to operate the flasher can, If it has a dead globe then it won't flash
willy
William Revit

Hi Tim

Get yourself to Halfords.

Barry
B Bridgens

Yes I agree that a fault in the wiring will not make a light bulb fail (unless you have much too much voltage which is very unlikely indeed). So as has been said, replace it and see, what happens.
If it still doesn't work, maybe test the earth first
Graham V

Hi Tim

I agree with everyone there is no way MGA electrics can create the extra voltage that would be required to blow a bulb. Of course the opposite is not true as if you have a fault that puts 2 in series they share the 12 volts creating a dim bulb.

I have now gone LED throughout as it strengthen the light intensity from our little lights useful in traffic.

Cheers
Paul Dean

Hi Tim,
I can't remember if you are running with a generator or an alternator on your MGA.

If it is a generator with a control box (the Voltage Regulator), the control box can eventually go out of adjustment, particularly the modern replacement ones which are often less well made than the original Lucas ones. For example, if the cut-out relay is not operating properly, the generator can be overcharging the battery, which could also possibly burn out the generator.
So it is worth checking the output voltage and to see if the cut-out is operating properly.

If you are running with an alternator, I know from personal experience that the output voltage can be much higher than it should be, I only found out after burning out two expensive electronic distributors.

My alternator was pushing out well over 20 volts and this was caused by my fitting an additional thicker output wire from the alternator output to the starter switch, as well as the original output wire to the control box.
This double wire set-up confused the alternators built-in voltage regulator , but once I deleted the original thinner wire, the problem was solved.

PS There is lots of info on MGA Guru about setting up the control box.

Cheers
Colyn
Colyn Firth

Thanks all. I'm going to have to do a bit more investigation. I did put another working bulb in and it worked okay but now the offside indicators aren't working! New bulbs also being obtained. I'll update the forum once sorted. Cheers. Tim
Tim Prime

New bulbs now installed and everything seems to be working okay. Thanks for all the comments. Tim
Tim Prime

This thread was discussed between 20/11/2021 and 24/11/2021

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