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Turn signal issues

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markbt73 Avatar
markbt73 Mark Tucker
Portland, Oregon, USA   USA
1971 MG MGB GT "Maggie"
I went out for a drive today, and at one point I made a right-hand turn that wasn't a sharp enough turn to cancel the turn signal. I ended up leaving the signal on for 3-4 miles. (The dashboard indicator is very dim, and I couldn't hear the clicking over the exhaust and road noise.) I finally realized it was on when I slowed down and heard the clicking. Felt stupid, hoped no one was looking (luckily there was almost no one else on the road), turned them off, and drove on. The signals worked twice more after that, and then quit working in either direction.

Now here's the thing: the flasher unit is brand new, an electronic unit from Moss. Could I have burned out the new flasher leaving the signal on for a few minutes? Seems unlikely, because you sit in traffic with the signal on for longer than that. Is there a way to test the flasher unit? Can I swap it with the hazard flasher (which does work) for a test?

Or could it be the switch? I tried all the other lights and the only other thing that doesn't work is the flash-to-pass side of the high-beams. Pushing forward turns them on, but pulling back doesn't flash them, so I know at least that portion of that switch is bad.

Any advice is appreciated.



1971 MGB GT - the project; 2002 Saturn SC1 - the daily driver; 1996 Ford Explorer XLT - the workhorse
"The more I learn, the less I realize I know."

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gofastandfalldown Avatar
gofastandfalldown Glen Horne
Edmonton, Alberta, Canada   CAN
1970 MG MGB MkII "Miss Pandora Moneypit"
You could do a few quick tests to isolate the problem.

Power for the turn signals goes through the hazard switch first, then the turn signal flasher, then through the turn signal switch, then gets routed to the left or right lamps.

If the turn signals illuminate steady, then the hazard switch and turn sig switch are ok---it is probably the flasher.

If the turn sig lights don't come on at all, try removing the flasher and jumper the 2 wires together.

Most often it is the hazard switch that is corroded inside. Try flipping it on and off a bunch of times and see if that helps.

Ex-Calif Avatar
Ex-Calif Gold Member Dan D
Cincinnati, Ohio, USA   USA
1968 MG MGB GT "Bart - Yellow And Naughty"
1977 MG MGB "Red Betty"
2012 Jeep Liberty "Tank"
2014 Hyundai Accent "Skate"
Be carefu, about "correlated" faults and causative faults.

The switch is common to the flash to pass and turn signal problem but may not be the cause. Troubleshoot each one separately.

You can make up a jumper and supply Brown power to the flasher unit post where the gree is currently attached. If the turns work it is the hazard switch, the wiring or the turn signal switch. You can bypass each item one at a time. A more "elegant" way to troubleshoot is the use a meter checking for power.

The flash to pass is on the purple power circuit. If purple power is available going into the switch but not out of the switch you can suspect the switch.



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