My passenger side rear turn signal is very dim when it blinks. The driver side is fine and both parking lights are fine. I swapped bulbs and also tried swapping wires and it's still dim. I'm guessing one of the wires has worn insulation and is hitting the frame. There's lots of splices and electrical tape at the back of the truck.


Since turn signals were only factory installed for some states the shop manual shows no turn signal wiring.


There are 4 wires going from the engine compartment to the back of the truck. 3 are bundled together and the fourth is separate.
In the engine compartment I cut the first one which cut power to the brake lights. I then reconnected it.
I cut power to the second one which cut power to the parking lights. I then reconnected it.
When I cut power to the third one both turn signals still worked (with the passenger side dimmer) but if I also turned on the parking lights the passenger side didn't blink. The driver side worked normally.
Does anyone have a wiring diagram for turn signals or any ideas on the issue.

 

The wiring diagram will depend on what type/brand turn signal you have installed. Color codes on the wires vary.


My truck originally had the Signal Stat 700...which had 5 wires.


Green - left front
Red - right front
White - left rear
Black - right rear
Yellow - flasher


When I rewired my truck the harness has 7 and I had to get a new turn signal.


this page my be of help. Yea its from a chebby but it lays out the wiring of a signal stat unit


Stovebolt Tech Tip -- Antique Chevy / GMC Truck Restoration Help

 

B4C-13341-A .. T/S Switch / Obsolete

1953/55 F100/600 / 1953/54 P350/500 Parcel Delivery.

B & L FORD in Ashland PA has 1 = 570-875-4417.

NOS PARTS SOURCE in Olathe KS has 1 = 913-220-5746.

 

Check and replace your ground for the light in question. Sounds like a typical ground issue.

 

Here is the diagram I did for my 55.



Here is one adding a headlight relay:

 

I'm pretty sure the turn signal were factory installed since there are directional arrows integrated in the gage cluster.
I already had an auxiliary ground wire from the body to the tail light but I noticed on the driver side the ground wire goes directly into the bulb socket. I'll have to try that on the passenger side.
I did find a fourth wire going from the engine compartment to the taillights. I haven't tried cutting it yet since it's bundled with another wire.
I'm just hoping the issue isn't a bare wire under the dash since it's very congested.
I wish I could find a complete wiring diagram showing the turn signal lights in the cluster.

 

Plus one on this, very common symptom of a poor ground connection...........

 

I ran a ground wire from the body right into the tail light terminating in the bulb socket. Now the light is brighter and it blinks with the parking light on too.
With the parking light on I now measure 5.8 volts. Before adding the ground to the bulb socket it was less than 3 volts. I'm still going to replace the 3 wires from the engine compartment to the taillights.

 

Good for you. I had to do the same thing with my taillights.

 

Glad it fixed your issue. It is always good when it is an easy fix.

 

I know you found the problem already, but here is the original wiring diagram for the factory turn signal.

The "Pilot" lights are the arrow indicators in the instrument cluster.

 

Thanks for the wiring diagram. It helps in understanding how the turn signals work.
I still need to figure out what the 4th wire was for.
1. Parking lights
2. Passenger brake/turn signal
3. Driver brake/turn signal
4. ?
All 4 are original wires. 1, 2 and 4 are bundled together. 3 is in a separate 1/4" diameter rigid cloth housing.

When I replace the wires I'll figure it out.

 

So your parking lights don't flash? If they do, the 4th should be the other parking light wire.
My switch has 6 wires.
1. Right Front
2. Left Front
3. Stoplight switch
4. Right Rear
5. Left Rear
6. Flasher/power

 

Thank you.
I traced the 4th wire. It comes form the fuel level sensor.

 

Effie, here is the challenge I have - using the diagram (and my factory installed turn signal 1954 F100 matches this perfectly), what is the rest of the connection from the brake light switch to the left turn signal? The diagram shows the yellow wire as the left rear turn signal, but how does that yellow wire tie into the wire coming out of the brake light switch?

A little more, the harness I have for the rear lights has three wires coming out of it at the rear (black for tail lights, green/orange for left turn signal, and orange/blue for right turn signal). The wires from the tail light assembly are red and black (so is the cross over to the right tail light assembly). How do I connect these wires at the rear of the truck? And whatever that connection is, should I assume the brake lights are going to work?