Hi, I'm wondering if anyone has had the same problem as me and if they can help. The side markers and turn signals are acting up on my 79 f100. When you turn on the left turn signal nothing happens, same with the front and back. But they all work when the hazard lights are on. I'm no electrician but if this is an easy fix please help. Thanks.

 

The hazards work using a different flasher unit. The one for your turn signals might just need to be replaced.

Put on your hazards and note which flasher under the dash is in use. Then replace the other one.

They look like this one: Flasher link

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You're saying the hazards work, yet the LEFT turn signal does NOT work - is it safe to assume the RIGHT side DOES work? If the hazards work and the right side works, you've proven out the bulbs, sockets, and turn signal flasher. The only thing left is the switch itself. That would explain why both LEFT FRONT and LEFT BACK do not work.

You can prove this theory by disconnecting the turn signal switch coupler under the column. Lock the turn signal lever in the RIGHT position. If your RIGHT side is working, you will see continuity between the BLUE and WHITE/BLUE wires on the turn signal side of the connector (NOT the side coming from the truck). Next lock the turn signal lever in the LEFT position. If you don't see continuity between the BLUE and GREEN/WHITE wires in the same connector, replace the turn signal switch.

 

Yea I have the same issue except it's both the left and right signals. They work every now and then, but once you push the brakes they stop working, hazards work just fine though. Maybe i'll try a new flasher. How to I get into the steering column to replace the switch?

 

Pull the wheel. To slide the switch out, you have to remove the connector at the bottom of the column by popping out the pin retainer, and removing each pin individually.

 

Any certain method on removing the wheel? I can get the nut off but not sure how to get the wheel off, it's on there.

 

Steering wheel puller, you can rent one for like 8 bucks, or just buy one for around 20.

 

Thanks. First I'm gonna try the flasher though. Can any of you tell me where that's at? It's not with the fuse panel along the firewall from what I can remember.

 

Both flashers just hang freely behind the dash in the general vicinity of the headlight/wiper switches.

 

Both have two prongs, so look the same, but the flasher used with the 4 way emergency flashers is a heavy duty unit, has a louder click.

The H/D flasher can be subbed for the turn signal flasher (and was with trailer tow), but not the other way around.

 

I chased similar tail light/side marker/turn signal issues on my truck for a couple months. New turn signal switch, new flashers, new bulbs, and they still wouldn't work right. It ended up being the actual tail light sockets. Ordered a couple new ones from LMC, and after replacing them everything worked great again.

 

1974 F100/350 Styleside taillamps from serial number T80,001, 1975/79 F100/350 Styleside taillamps are the same as 1975/91 Econoline and 1978/79 Bronco, as are the plastic 'twist-in' taillamp & backup lamp sockets.

The only difference in these lamps is the Bronco/Econolines have a foam rubber seal that just peels off.

Lotta 1975/91 Econolines in junkyards, so there's no need to buy these parts from LMC and then pay shipping charges from KS to lawd only knows where.

 

Well I put a different flasher in and they work again. They work but whenever the engine is still running a little low at idle from a cold start they don't work until the idle rises from running. Still work though now so I'm happy.