Hey guys, my most of the time, not all the time, when i turn the head lights on the left turn sinal light will stay on, and the turn signals dont work when the running lights are on. Any clue whats going on? Thanks guys.

 

When I turn the head lights on the left turn signal light will stay on-

On the dash or outside the truck?

If it is in the dash then check the front blink lights in the grill. The sockets will rust out and not function, Making the light come on in the dash.

It's the old style burned out bulb indicator warning system..


Turn signals dont work when the running lights are on-

Check the wiring to the taillights, the PO had mine wired wrong and the same thing happened.

 

Alright thank you and yes its in the dash, ill chen it out this evening, how was the wireing wrong in yours?, just to give me an idea of what im looking fot

 

Well except the front left, i suspect the socket that deffenantly wasnt right. the hazards work, switch maybe? Abd claning the sockets got rid of the constant light.

 

This is a classic case of bad sockets up front. This shows up the way it does because both filaments in the 1157 bulbs share the same ground. Your turn signals don't work with the running lights on because of ground shift, due to the ground in the socket deteriorating. Your turn signal indicator in the dash comes on with the headlights on because your front running lights can't seek ground in the socket, so it backfeeds through the other filament and into the dash.

Replace both front sockets.

 

D1FZ-13234-A .. Park Lamp Socket

Applications: 1974 F100/350 from serial number T80,001 / 1975/79 F100/350 / 1975/91 Econoline / 1978/79 Bronco // 1971/73 Pinto/Bobcat/Mustang / 1973 Torino / 1975/78 LTD.

 

This should help you out. On the taillights, 3 wires, One ground and 2 power, one for running lights, one for turn signal. On mine they had a power wire to the ground and the running light power on the turn signal side of the bulb.

 

HAH wow man i have the same problem except my blinkers dont work at all, and when i pull the switch into running light or headlight the right blinker indicator will light up. one day this past summer it stopped and the blinkers worked for several months and one day back to the same way. one thing i do notice is that one of the parklights is much dimmer than the other also, i cant remember if its the same side or not.

i just assumed i need to replace the 63 dollar ts switch which aint happenin lol!

im going to rewire all my front lighting harnesses as the wiring on this truck is so hardened that insulation will crack if i bend any wires around.

i also pulled both the flashers out one day to see if the light would go out and it stays on still too, idk if that tells anybody anything?

 

Having a good ground will fix alot of problems with these trucks. Also having good light sockets since these trucks are over 30 years old.

 

I suspected the socket, the drivers dide front is messed up, at the power teminals, i cleaned the ground prong and its shiny, lights on or off they dont work, however the hazards work cept front drivers. Randomly going down the road they worked then quit again. That was with lights off.

 

Update, left front flashes, but the running light filament wont shut off, good socket that i know works too, im checking this with the hazards turn signals still dont work

 

You have to actually REPLACE the socket. The problem is INSIDE the socket; cleaning it will not help.

If you were to ohm out the socket with a multimeter, you would find it's actually bad. A multimeter is the only tool you can use to measure electrical. Visual inspection doesn't help you.

 

Yest i know that im an electrician, the socken ohms out fine, the old one did too after i cleaned the ground. However the terminals were screwed up and it was a pain in the rear the get the lamp in and out. Checking with power and ohms the lamp holder is fine, both filaments light up, but both at the same time, this is now the problem im trying to figur out right now. The turn signals i think is the swith, its hard to switch and feel gritty. As well as the turn signals randomly working.

 

I had the exact same problem on my 78 and I replaced both left sockets and bulbs. Everything is perfect now. This thread was extremely helpful!! Thank you all!

 

Is there a fuse that is used for the lights in the front or the rear?

I've got some strange things happening under my dash with my wiring... likely from the P.O. chopping everything up real good...

1) My left turn signal pulsates at the same rate my truck pulsates (it doesn't idle consistent).

2) Some of the wires under my dash in the big cluster that goes directly behind the radio are starting to heat up really really badly and they're actually melting through the electrical tape and anything plastic that's touching the wires...

Any idea what's wrong with #2?

Number 1 sounds like it's just a socket or bad ground.