Minor electrical gremlin

Hi folks,

Went out for a little drive yesterday, and discovered that I get a double flash of the nearside indicator (like a bulb has gone) but only when I'm applying the brakes (so brake lights are on). Take my foot off the brakes and it goes back to normal. I'm suspecting an earth at the rear.  I cleaned up the earth point on the boot floor as part of the rebuild, and all the bulbs are new.
Any suggestions on what to check and how?

Thanks!

J
 

kinda sounds like a short. so the resistance is being lowered somehow when you hit the brakes which i guess is causing the double time flash of the indicator (flashes at twice the speed because of lower resistance) so presumably a short somewhere………just a guess. Might want to try a new bulbs and particularly in that indicator. I had previous problem took me ages to find because the darn bulb was bad even although it was brand new. and flashing at twice the speed so no way did i suspect the buld. Tore the car half way apart and then decided to change bulb out again and bingo. the internal resistance of that particular bulb was less because of some reason, still no idea why but it worked after i changed the new bulb for another new bulb. you could try swapping bulb from that indicator to the other and see if you can move the fault ie if it does it now on the other side of car. and take a bulb from good side and put in side thats not working and see if you can move the problem. if you can then you know its the bulb for sure, if it still does same thing then you for sure know its wiring or something but its not the bulb. I would also do same with brake light bulbs too just incase. 

Check there's no corrosion throughout the bulb holder and terminal plug, maybe try a temporary earth direct to the bulb holder also

You aren't using LED bulbs? I have seen bulbs that are dual filament go, and the filament that burned fell against the good filament and well it caused a similar condition.

Check your bulbs with a meter, Also check the ground at the bulb to the frame, if it isn't 0 ohms then then that is your issue as it could be phantom grounding.

On my 81 I eventually ran a new ground from the rear bumper mounting bolt with a large ring connector to the
bulbs, one for each side.

Lesson learned and applied to my Cabriolets…
I would also validate no Voltage drop from the battery to frame as the front battery-to-frame-engine cable OEM was a stranded Copper, that was a single piece unshielded and corroded with road debris/salt.  The OEM cable I had on my Golf I took off and allowed to soak in a Vinegar solution for a couple of days and it turned from a green brown to shiny copper and I gained a good 1.5VDC on my alternator/battery.  

That's some good cable info Briano1234, I'll keep that in mind for my car. Im putting the wiring looms back in just now and some of my cables are nasty looking so will do that with the vinegar too.

Thanks chaps - plenty for me to look at when I get the chance. I'll report back with my findings….

J