crazy light fix

[suttonsd]

I bought a 67 f100 that none of the rear lights worked. It was getting power to all the sockets. I figured out that the bed was not grounded to the frame because of the rust on the frame. I ran a new ground from each of the rear tailight frames and now it works grreat. i justed wanted to let anyone that might have the same problem what i did to fix it. I hope it can help someone that might be scratching their head.

[fordman]

that also happens on other trucks that use wood blocks between the frame and bed.

[retriever47]

I wonder if that might be part of my problem. I rewired my rear lights in my 67 F100 because only one was working and everytime I tried to fix it the other light wouldn't work then. After rewiring everything works but the turn signals give me the rapid flashing which is supposed to indicate a burned out bulb. I have triple checked all the bulbs and they are all good. All the turn signals work but only in rapid flashing mode.

Anybody have an idea what might be causing this? I think I'll add a ground between the light assembly and the frame.

Any thoughts would be appreciated.

Thanks

R

[TNIceWolf]

Could be a weak flasher retriever.

[m-mman]

The "ground" circuit going back to the the battery has been called the 'invisible' wire.
Because you cant see it, it is easy to forget it is an essential part of any circuit.

Thanks for remembering to post your experience and add to our knowledge base.

[rjewkes]

I think thats the frustration as i remember chevies batteries mostly ground to the frame and then the engine from the frame. and then ford goes the other way engine, then frame and also firewall.

[retriever47]

tnicewolf,

I'm not familiar with the flasher, what exactly do you mean be weak flasher? Is there a flasher module/unit? Where is it located? Anyway to test it when I find it?

[70_F100]

Yep, sounds like a bad/weak flasher.

The flasher is the device that makes your turn signals flash. The most common types are resistance or mechanical. The one that works on resistance relies on the resistance of the bulbs to heat up a miniature coil which in turn pulls in the second leg of the wiring. It's basically a relay. The mechanical ones actually have a motor inside. The third type I'm aware of is totally electronic.

Either way, it should be a round "canister" that is about an 1-1/4" in diameter. It may be about an inch long, or it may be about 2-1/2 inches long. Or, you could have a rectangular one, about 1.5x.75x.75. Hard to say what a PO might have put in a 67 in the last 40 years.

Look under the dash, to the left of the steering column. This should be (whether round or rectangular) an aluminum case with 2 wires going to it. Some, however, have a clear plastic housing.

You can pick up a replacement at any auto parts store. Your best bet is a heavy-duty unit designed for cars/trucks that will pull a trailer. If you get one that is designed for only 4 lights (front & rear turn) and you decide to pull a trailer, the turn signals will blink extremely fast due to the added resistance of the trailer lights.

[fordman]

if you cant find the flasher can on the left of the dash. it may still be hooked to the back of the instrument cluster. you will have to reach way up in there to get at it. or remove the instrument panel to get at it.

[QC]

There are 2 flashers, 1 for the turn signals and one for the 4-ways. If your 4-ways work it could be the turn signal flasher. Just swap them and see if there is any change.

[70_F100]

Good point, QC.

Undoubtedly, though, he needs to replace it. The old resistance-type units were notorious for creating the kind of issue he has, especially on Fords.

Never saw it much on GM or Chrysler. They just stuck on and didn't flash at all when they failed.

[sideoilerfe]

...Never saw it much on GM or Chrysler. They just stuck on and didn't flash at all when they failed.

Not on my '75 Dodge Dart. When the flasher failed I had no signal at all. Nothing stayed on and nothing blinked.

[70_F100]

Good point.

They did one or the other, but the Fords flashed really fast, almost so fast you couldn't tell that it wasn't steadily on.

One point, though. You're talking mid-70's.

I'm THINKING mid-60's.

Communication failure... LOL

[fordman]

i was told that the hazards had a heavy duty flasher and if you put the headyduty flasher on your turn signal side also. that it would make the turn sigala faster even without a trailer. i cant remember if i have ever tried it but i do remember a guy named barry told me that. he was into these trucks back in the late 80's early 90's.

[FORDTOUGHF100]

Suttonsd,
Where did you ground the rear lights from and to where? Can you give a description of what to do? I don't know where to start. If SuttonSD can answere can someone chime in? Thanks.