Vote: turn signal switch?

[machoneman]

Just realized yesterday on the drive home the turn signals on my '70 Mach 1 stopped working. Replaced the turn signal flasher but only then realized the 20 amp fuse was blown. Replaced it and the fuse immediately blew again. The separate emergency flasher works, brake and running lights work and it seems the printed circuit board for other dash functions is o.k.

Hate to do it without some advice: I'm guessing the in-column turn signal switch wires got chafed and it is causing the short.  I know this is a weak point on older 'Stangs but I had replaced it years ago.  Pull the switch?

[jayb]

I would disconnect the turn signal switch connector and use an Ohm meter to see if there is a short in the switch.  If you've got the wiring diagram you should be able to figure out which wires are which, and determine where to look for a short.  I HATE pulling those switches; check it electrically before you go through all that...

[machoneman]

Thanks Jay....I hate to do so as well but.....

[machoneman]

Yup! One of the cam-operated turn signal wires on that moving nylon cam has 50 times the resistance of all the rest that read at .02 ohms.  Darn, the harness in the car now is a knock-off, new in '94 and not that many miles on the car either.

I just bid on E-Bay (pricey!) for a never-used, in-the-box, NOS Ford harness. Be damned if I'll put back in another cheap knockoff...not that it was that cheap either. 

[jayb]

A good double check would be to install the fuse with the turn signal switch connector unplugged, and make sure it doesn't blow.  Two problems at once can happen...

[cjshaker]

It seems odd to me that it would have high resistance. If even ONE strand of wire is still connected, that is enough to give a zero resistance reading since it's a really really small current that an ohm meter uses. Try a check to ground (or the column itself) to see if it is shorting in the column.

High resistance usually indicates a bad connection, so it may just be a simple connection in the switch that has worked itself loose over time. It may be as easy as re-pinching a riveted connection where the wire contacts the switch. Or maybe you could solder it for a more solid connection.

[machoneman]

A good double check would be to install the fuse with the turn signal switch connector unplugged, and make sure it doesn't blow.  Two problems at once can happen...

Good idea and I'll do just that. Thanks.

[machoneman]

It seems odd to me that it would have high resistance. If even ONE strand of wire is still connected, that is enough to give a zero resistance reading since it's a really really small current that an ohm meter uses. Try a check to ground (or the column itself) to see if it is shorting in the column.

High resistance usually indicates a bad connection, so it may just be a simple connection in the switch that has worked itself loose over time. It may be as easy as re-pinching a riveted connection where the wire contacts the switch. Or maybe you could solder it for a more solid connection.

Agreed. I will pull the entire switch but....that nylon cam pivots on a small solid metal post and is held down by a tiny Tinnerman and the post is then peened over. Methinks something with the L-R contacts has gone adrift and I've never had good luck prying off those Tinnermans and then getting the post peened again well enough to hold things down. We'll see and thanks.