OK. I searched this forum and didn't see a thread about my problem so here goes. I have a 1970 F100. The signals quit last week. I repalced the flasher. No luck. So I replaced the turn signal switch today. Still no luck. It's the same as before switch replacement. Signals will light but not flash. I have brake lights and when I pull on the emergency flasher, the signal lights work fine, just no turn signals. The Chiltons manual doesn't give a lot of info and I don't have access to a shop manual. I need to know where to go next. Oh. I almost forgot to mention that I did install a hitch and trailer light harness last year. Do you think that where I tapped in the wires could be the culprit? Just trying to be logical in troublshooting......just stumped on where to look next. Thanks in advance for your replies.

 

I'd look at where you cut into for the trailer harness and see how it looks. Did you use any crimp-style connectors back there? If so that could be the problem. It's a good idea to avoid crimping on anything that will be around the elements. I'd also take a look at your grounds at the bulb sockets. That's odd that you have hazards but no signals; maybe you had some bad luck and got a bad switch?

 

If all the correct lights come on when you move the signal, but they don't flash, then you do not have enough load on the turn circuit to make the turn flasher work, but apparently there is enough load to make the hazard flasher work.

There are several reasons this could be happening, such as the wrong bulbs, the bulbs wired backwards in the sockets, or a poor connection somewhere. But if all the bulbs look bright, and you also have a trailer hook-up, I would go ahead and get a heavy duty flasher. The heavy duty(or electronic type would work too) do not depend on the bulb load to flash. You will definitely need one anyway for the trailer, since when it's hooked up, the flasher will flash very rapidly.

 

Franllin2, isn't the 552 flasher the heavey duty one? That's what I have in there already. I was just at Advance and saw an elecdtronic type you mention, code EL12 I think it said. Should I invest the 10 bucks in one? What do you think? Just grasping at staws...............

 

No, I looked it up on their site and it's a regular thermal flasher. It says in the description it can only handle up to 4 bulbs. Looks like the electronic one is the only one they have in stock, though the internet site and the actual store differ sometimes.

They list the heavy duty as FC536.

 

Franklin2, Thanks for your replies. I'm always happy to learn more information. I have to admit tonight that I made a mistake.Turns out I didn't need a new switch after all. A buddy at work pointed me in the right direction as to my signal problem. Short version, he insisted that there had to be a second flasher that was my problem. The one I thought was for the turn signals was actually the hazzard flasher. I had been under the dash searching for the turn flasher and didn't see or "feel" it anywhere. It turns out that it was conceled behind the wiring for the headlight and wiper switches and the cluster support frame. I unscrewed the cluster and moved it out of the way during lunch time and there it was. I happened to have an extra 552 flasher in the glovebox, put it in, and instant sucess. Hopefully, the next person that searches this forum for answers will see these posts and learn from them what not to do, like I have. I hung the old flasher from my rear view mirror as a reminder to be sure to check everything thoroughly before assuming something needs replacing. I will check this weekend on the flasher you posted about and see what I can find. I guess the best lessons learned are the ones we learn the hard way. ( and sometimes the stupid way )

edit: fmc400, I checked the harness connections too. They were ok. Thanks for your input too.

 

There are TWO flashers on these trucks. One is for the turn signals, the other is for the emergency flashers. Both are located near each other behind the dash.