Ever since i bought my 78 f100, the dash turn signal lights stay on when the lights are on. Turn signals and hazard lights work fine, and I have replaced ALL the bulbs, and both flashers.

So...is this normal??

 

Nope. It's not. I have a similar problem with my truck, but one of the turn signals just straight up, won't turn off.

Check your fuses and all of your wiring to see what's up. Maybe you have a bad connection somewhere in the truck... these old beasts are infamous for them..

 

I"ll deal with it for the time being. When the bed comes off in late march / early april for painting, Im going to rewire from the cab back anyways, so I guess i'll check it out then.

I hate wiring!

 

when the turn signal lights are lit are they bright like when you have the turn signals on or are they kinda dim? if they are dimly lit, you could be getting light from the gauge cluster lights shining through the turn signal lenses making it appear that the turn signals are "on".

 

No, they are bright...

 

Sounds like a grounding problem to me. I've never had that problem with my '68 F-250 and I just got my '73, but I've had to clean the ground at the light several times on my International to get'em blinky.

JW

 

That's ALMOST the problem I'm having.

My problem is that the wiring seems to be screwy. The turn signal comes on and stays on when I turn it on. When it's off, it pulsates with the alternator (or that's what i looks like), and it's very dimly lit, but it's almost like it's running when it's off. The right han signal doesn't do this, but the left hand side one does...

No idea how to fix this, but it'll be part of re-wiring my truck.

 

have you guys checked the light bulbs (turn signal bulbs) on the front and rear of the truck (not the dash turn signal bulbs) for good grounds? correct light bulbs? light bulbs installed correctly (they can be put in incorrectly if forced into the socket). The other thing might be some wires / contacts touching each other in the turn signal switch in the steering column. just a thought.

 

This is the same problem that mine had when I first got it. Turned out to be bad grounds and one bad socket in the tail light.

 

This happens when there's a bad ground in one of the bulb sockets. If it happens when you pull out the headlight switch midway (to turn on just the front parking lights), then it's the turn signal sockets up front. If it happens only when you pull out the switch all the way (to turn on the headlights), then it's the tail light sockets in the back.

The reason this happens is because both filaments in the 1157 bulbs in the front turn signals and tail lights share the same ground. The turn signal indicators in the dash use a different ground. Ideally both grounds are at the same potential, but as the socket ages, the ground in the socket is lost. When you turn the lights on, current flows through the parking light (or tail light) filament but can't find ground at the socket, so it flows through the turn signal filament, up through the dash, and finds ground through the turn signal indicator filament. This makes the turn signal indicator glow.

When this happens, however, the turn signal indicator usually glows dimmer than it would if the turn signal was actually flashing, because of the voltage drop caused by the parking/tail light and turn signal filaments. You and I may have different definitions of bright, however. If it's shining bright as day just as if the turn signals were flashing, then wires might be touching. You could easily verify my original suspicion with a multimeter by checking for continuity between the socket ground and true ground.

 

fmc400, that is some very good info. Thanks. Once it warms up a bit today I'll go out with a multimeter and check all my sockets and grounds. This truck had serious ground issues when i first got it, caused me to smoke a few wires in the starting circuit. So im going to bet anything that a ground is to blame here.

Plus, you hit the nail on the head. The front turnsignals are very dim compared to the back turn signals, and like I said, all the bulbs are new.

Thanks!

 

the isue i found with my 77 is that its the turn signal part on the steering column. if i just move the lever a bit it will go out. i just need to pull the steering wheel to get at it.

 

I also need to do this. I'm positive that my turn signal switch isn't working properly. I need to buy a steering wheel puller that has a flat end on it for these old trucks and yank the steering apart to get a good look at what's all going on.

 

It turned out to be a bad socket up front for me when I went through this problem as well.

 

It's surprising that something so small can cause so much hassle. I'll definitely look through my grounds and sockets.