Headlights turn off turn signals

[Mel429BirdT]

All of a sudden, my turn signals won't work with the headlights on. If I turn the headlights off, the signals work. I can get them to work by manually moving the turn indicator lever, but a few years back I had to replace the turn signal apparatus at a cost of over four hundred ($400.00) and I don't want to wear it out again prematurely.
I understand that 1971 T-Birds were prone to electrical problems and I seem to be living proof, but I still love the car.

[KimMG]

Do you have a wiring diagram for the car? Systematically check the wiring and components in the two circuits using a meter or a test light. Make sure all connections are clean and secure, including where wires connect to the body for grounds. After you clean a connection, use dielectric grease on the connection to prevent future corrosion. Look for wires where the insulation may have been rubbed off.

[consultant]

Originally Posted by Mel429BirdT

All of a sudden, my turn signals won't work with the headlights on. If I turn the headlights off, the signals work. I can get them to work by manually moving the turn indicator lever, but a few years back I had to replace the turn signal apparatus at a cost of over four hundred ($400.00) and I don't want to wear it out again prematurely.
I understand that 1971 T-Birds were prone to electrical problems and I seem to be living proof, but I still love the car.

Do you have fog lights, and use them a lot?

I had a problem with my '93 where using the the high beams would turn off the lights - makes for an interesting night drive! The dealer said the switch wasn't rated for the load (it was replaced under extended warranty)

On my '96, the multi-function (turn signal, etc.) switch costs about $50 and takes about an hour-and-a-half to replace. You don't have to drop the steering column or anything like that - just remove the iginion key lock cylinder (done with a drift pin to release it in the run position - see the shop manual for details - or buy the CD-ROM Ford service manual on eBay for $10 ) remove both halves of the plastic collar around the steering column and you can remove and replace the switch.

Dealers will rip you off for these kinds of repairs -