Brake lights fusing - not while parked, only when running

Happy new year!

Thanks for advice re metering etc. I now believe there are a couple of faults - the wiring for rear brake lights is definently goosed. I've replaced this in a hashy fashion for the moment ( from front to rear rhs then through to Lhs and back up through tub - I'm hoping that I go back and fix this quite soon but these "fixes" have a nasty habit of ending up permanent!). This has indeed sorted out lights and fusing issue. I think there may be problem with the alternator, as when checking voltage it went from 13.4 up to 17 or at one point 19v. Whilst just idling. So something else to replace!

Thanks again for the help and advice..
Cheers
Ken

Kennymac said:

Happy new year!

Thanks for advice re metering etc. I now believe there are a couple of faults - the wiring for rear brake lights is definently goosed. I've replaced this in a hashy fashion for the moment ( from front to rear rhs then through to Lhs and back up through tub - I'm hoping that I go back and fix this quite soon but these "fixes" have a nasty habit of ending up permanent!). This has indeed sorted out lights and fusing issue. I think there may be problem with the alternator, as when checking voltage it went from 13.4 up to 17 or at one point 19v. Whilst just idling. So something else to replace!

Thanks again for the help and advice..
Cheers
Ken

Click to expand...

and your headlights dont get brighter when you rev it ?its a common tell tale for alt throwing out too much voltage

No headlight flaring, which is a bit odd as I'd expect that with fluctuating voltage...

Forgot to say, revving doesn't change voltage variation, just idling the voltage read goes up and down like yo yo. When you Rev it, it dies the same thing with no perceptible difference in volt reading..