TR6 Turn signal lights don't flash when under load.

Has anybody run into this issue. The turn signal lights flash when the headlights are off; when the headlights are turned on, the lights come on, but don't flash. Is this a problem with the flasher or a lack of power from the alternator? It's a 1976 TR6.

My turn signals slow down when the headlights are on. If your battery is strong then your flasher unit must be weak.

Sounds like the voltage to the turn signals is dropping when there is a heavy electrical load. That could be the battery, alternator, or just old, resistive connections. I think I'd get onto it with a voltmeter and see where the voltage is getting lost. Start at the battery, and if its voltage drops significantly when you turn on the lights, the battery is weak or its not getting charged well. The latter might be the charging system or maybe you just aren't driving enough to keep the battery charged.

If that checks out, it's time to start tracing through the circuit and seeing where the voltage is dropping, and go from there. Might be several places.

Thanks for the replies, Steve I did as you recommended and traced the voltage. The problem turned out to be the battery terminals needed cleaning. They looked good from the outside, but not so good when I removed them. Thanks again.

Ah, yes, that's a classic. Glad you found it.

I had a similar problem last year. Replaced the battery, cleaned terminals, etc with no relief.

Eventually I replaced the original 45 year old turn signal flasher relay with a new/modern electronic unit and the problem went away.