I just finished up re-wiring my 62 F-100. Everything works except the right rear turn indicator. The brake and park lights on that side work fine, but with the right turn signal on, the lamp is dark. Right front and right dashboard indicators flash just fine.

Looking at the wiring diagram, all I can think of is that the switch has gone bad. I hope that is not the case. Is there something I'm missing?

~Steve

 

Since both elements of the right rear bulb work (running lights and brake lights) that eliminates any wiring issues to the back. I'm a little surprised the flasher unit flashes at the normal speed with only the front right bulb (and instrument panel indicator light) illuminating. I'm afraid I (like you) would suspect the turn signal switch. Good luck!

 

+2 I'd start with the grounding, clean up the contact areas.

You do have a double filament bulb back there, right? The tail light and the brake are using separate filaments, right?

The tail uses one filament and the brake-turn share.



John

 

Yep, the brake is considerably brighter than the park/running light, so it would appear that the ground is ok and the bulb is correct.

Looks like LMC has replacement switches . . . I guess it was time to look into the squeaky column anyhow.

Thanks for the help.

~Steve

 

I would start at the faulty tail light, make sure the bulb is correct. Had similar issue and found both contacts inside the bulb socket, and the socket housing itself were corroded which effected the circuit. If there's a license plate circuit that ties into the taillight harness, make sure the splice is clean, bulb and housing is free of corrosion, with clean ground surfaces. I would also check the connector at the point where the wiring exist the steering column; as well as, the tail light harness connection. I like to add a dab of dielectric grease to connectors.

 

Thanks, Dave. I will double-check the bulb, but since it does illuminate on the brake and tail light circuits, I suspect it's ok. All new wiring except the wiring through the column to the switch and the pigtails at the socket. No connectors in the circuit; everything is wired straight through, soldered and protected under shrink tubing.

~Steve

 

Steve there should be 3 wires going to the rear. Turn signal share with brake. Since brake is lighting the bulb and signal is not, you need to find the rear turn and get it on that wire.


John

 

There's nothing that reinforces my feeling of stupidity more than forgetting to realize the solution is usually simple. Double check to make sure the pins on the bulb are in the correct slots...a long shot, but you never know!

 

Update on this, as it appears to be more complex than I thought. I replaced the turn signal switch, which was clearly bad. (Over the last couple of weeks, it stopped working in both directions.)

New switch works well, and lubing the self-canceling mechanism will save a lot future embarrassment, too.

Unfortunately the right rear signal light still fails to illuminate. With the lens off, I can see that the brake and lights both--oddly--illuminate only the dim filament. Turn signal doesn't do anything. Brake + lights (and brake plus turn signal) = no light.

The socket tested fine on the bench. I traced the wires back and they checked out as well. I'm guessing that there's some kind of internal short in the socket. The bucket is not reproduced that I can find, so I'll try replacing the socket next week. If that doesn't do it, I'm stuck.

~Steve

 

Did you disconnect the wiring at the rear left frame rail and put a test light on the green wire with the turn signal on?


The test light will flash if everything back to that point is working.


Then its a matter of troubleshooting the problem from there back.


You can remove the left housing and plug it into the right side to see if it will work, just remember that the housing grounds to the bed. That will tell you if the problem is in the wiring or the housing.

 

I know it may sound silly but make sure the ground is good on the housing and to the sheet metal and to the frame and so on . As load increases with amp draw bad grounds tend to create mysterious problems . The brake light should never light up the smaller filament in conjunction with the taillight , you could have a short between those 2 wires .

 

Steve you have a grounding issue. If both filimants glow but not brightly it is lacking horsepower if you will, not enough to run it. It needs both intake and exhaust for it to run. Sand both sides of the screw hole area where the bucket fits the sheet metal. Brakes and turn signal share the same wire & filimant.

Do you have turnsignal on the front?



John

 

Yep, front turn signal and the indicator on the dash blink on the right as long as my foot is not on the brake. In that case, the dash indicator glows solid.

I'll clean the screw holes to improve the ground, but even with a poor ground, the smaller filament should not illuminate on the brake circuit--something else must also be amiss.

Shadowrider--hadn't thought about swapping the taillights to test. I'll give that a try.

~Steve

 

I also thought my small filament was glowing. It turns out it was not, the other one is so bright it made the smaller look like it was glowing.

 

Thanks for sticking with me through this problem. I spent another quality afternoon with the truck and my soldering iron. I replaced the contacts in the right rear socket, cleaned the socket tube (it's badly cracked, but still works) and cleaned the areas where the bucket grounds to the bed. Because this is part of a larger re-wiring project, everything now is new from the battery to the bulb.

The filaments on the right rear now appear to burn correctly. When I turn on the light switch, the dim filament comes on. The brake illuminates the bright one. Right turn blinks the dash indicator and the front light at a normal pace, but the right rear doesn't light up (and meter readings on that circuit are 0).

If I plug the left rear turn indicator into the right rear circuit (in the cab, by the steering column) the right rear blinks normally with the front left--nice and bright. To me, that indicates that the circuits and grounds at the rear of the truck are ok.

If I understand the turn signal circuit correctly (ha!), power feeds into the turn signal switch from the flasher and is shunted to the left or right circuit by the switch in the column. If that's right, then the problem must be in the switch--which I just replaced. What are the odds that the old switch and the new had the same fault?

Ug--I'm at a loss. Any suggestions are greatly appreciated.

~Steve