Turn Signal Wiring Gremlin

Theorangetiger

Theorangetiger

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Working out the details of a MKII I'm finishing assembly on, the only electrical issue is with the left turn signal. With the parking lights off. both signals work perfectly. when I turn on the parking and/or headlights on the right signal works fine but the left stops working all together - front, rear and the indicator on the dashboard. Turn the lights off and the signal starts working again.
I haven't checked it yet but figure the ground on the left side tail light housing could be the culprit. Am I barking up the right tree here or any other suggestions?
 
Theorangetiger said:
Working out the details of a MKII I'm finishing assembly on, the only electrical issue is with the left turn signal. With the parking lights off. both signals work perfectly. when I turn on the parking and/or headlights on the right signal works fine but the left stops working all together - front, rear and the indicator on the dashboard. Turn the lights off and the signal starts working again.
I haven't checked it yet but figure the ground on the left side tail light housing could be the culprit. Am I barking up the right tree here or any other suggestions?
Click to expand...
The turn signal/side lamp housing is not grounded to the body. with the lights off the turn signal is grounding through the marker light. when the lights are on, there is no path. this is a REALLY common problem! connect a ground wire to the housing and to a convenient spot on the body... then all will work as intended!
 
That was it. I ran a wire from one of the housing mounting studs to one of the trunk panel trim screws and all is good. Didn't even drill any extra holes. Thanks Sean!
 
Austin Healer said:
glad I could help!
Click to expand...
Just a recently observed difference: A Triumph TR 250 I am restoring has a complete daisy chain of companion grounds run everywhere both thru the harness and at remote devices. Nothing was left to chance. Interesting, just sayin' .
 
The original way of grounding the rear lamp assemblies was the use of an external tooth lockwasher under the wing nut. The lockwasher will "bite" through the paint on the backside of the fender and provide a path to ground. If you put a flat washer on the stud before the lockwasher it has no way to cut through the paint and establish a ground. There originally was no flat washer used.

Restorations usually are a lot better painted than the original car ever was. Thicker paint on the inside of the panel often prevents grounding. This is an issue with the front marker lamp housings as well. On the front units, the speed nuts were meant to cut through the paint in order to provide a ground.

Other areas where poor grounding can cause problems are the fuel tank sender and the w/s wiper switch. I usually run a ground wire from the left tank (drilled through the flange) to a spot on the body that would be unseen when the trunk panels are screwed in place. The wiper switch was originally grounded to one of the gauge retainers (same as the panel lamps), I usually reroute this to the outboard bolt of the lower dash pad which is welded to the body and provides a positive ground location.
 
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