When I turn the headlights on both filaments in my tail lights come on.


The turn signals will not work when the headlights are on, but will work when the headlights are off.


I checked the harness at the tail lights. Brown is tail lights, yellow is left, green is right.


What should I check next?

 

I would check the grounds.

 

park lites are grounding thru the ts bulbs. check ground to bed and light body to bed ground.

 

Some progress. BTW: 1964 Flareside.


I removed the front bulbs and cleaned the contacts. They fit in the sockets very loosely, I had to fiddle with them to get them to come on. The fronts now work as parking lights and turn signals. (On a 64, the park lights go out when the head lights are on)


Am I going to have to replace the front buckets?


On the rear Im still getting both filaments lighting when the tail lights are on. Is that a ground problem? The TL brackets screw into a threaded nutsert on the bed, so I think that Im getting a good ground from the housing to the bed. I hooked battery cables to the housing and frame but that didn't do anything.

 

To keep it simple, power has to get to the bulb filament for it to glow. If both are glowing, both are being powered, either by direct input or bad grounding back flow.

While this can be aggravating as all get out, it is usually pretty simple when you resolve it. I believe I can speak with authority on this, if it weren't simple I couldn't do it. My 66 would be a daylight driver only.


John

 

Not entirely sure about the park lights in your truck, but in other Fords of this vintage, the socket is replaceable by itself. Typically, the old sockets crack and get loose, as you describe. Something like this would be a replacement:


~Steve

 

I just went through a similar situation with my 65 F-250. It turned out to be a ground issue (my bed wasn't properly grounded) I drilled a hole in the light housing and ran it to my bed. Fixed it right up.
Hope it helps!

 

I added a ground wire from the bed to the frame today. The tail lights screw into the bed so I know that I have a good ground from the housing to the bed.


Could a bad ground on the fronts be causing both my rear filaments to light?


I ordered new lights for the front, DC shipped them today.

 

Don't presume all is clean on those taillight connections, verify.


John

 

Any idea what this is and where it plugs into?


1964 F100 292/AT

 

I am going to suggest that it is rigged, and very likely for back up lights. I don't think that is 64 factory.


John

 

Backup lamps introduced in 1967 F100/350's. With A/T, are operated by the NSS located on the steering column thru 1977.

With 3 M/T, backup lamp switch located on the bottom of the steering column under the hood. 4 M/T backup lamp switch threads into the shift tower.

 

Since no one recognizes it, I will take it off and see if it is connected to anything in the column.


It looks to me like it belongs there and it fits the column.


I don't have backup lights, but I don't think the flare is the original bed since it is in perfect condition and the truck is a CC.

 

I may be mistaken, but didn't Number Dummy just identify that as your neutral safety switch?

 

SS, I understood that ND was not identifying that connector as the NSS, but giving out general information about backup lamps. Perhaps I misunderstood?

The NSS uses a different plug connector than what is in the picture.

I believe the owner's truck uses the same turn signal switch as '65 and '66, possibly later.
If so, then that 2-wire plug is for the taillights, according to the electrical diagrams that I have.

John - Banjo -