Can a defective turn signal switch cause just one taillight to not light up?

[Kern Dog]

I've heard some stories about aftermarket ignition and turn signal switched for classic cars.
I'm working on my 72 Duster. I put a 69 Valiant grille in it years ago but just recently got the headlights and parking lamps working after swapping in a new switch.

I tested a couple of used ones, each had something wrong with them.
With the reproduction switch in place, the left taillight socket gets no power for the running light. Is this a common thing?

 

[RustyRatRod]

Yup. Wiggle the switch lever around with the lights on and see if the offender will come on. There are no GOOD switches available right now. So new in this case ain't good.

 

[413]

Running light, no it doesn't go through the turn signal switch.

The brake and turn light do go through the turn signal switch.

 

[RustyRatRod]

Running light, no it doesn't go through the turn signal switch.

The brake and turn light do go through the turn signal switch.

You should look at a 64 wiring diagram.

 

[Bennoel 10]

Yup. Wiggle the switch lever around with the lights on and see if the offender will come on. There are no GOOD switches available right now. So new in this case ain't good.

I agree

 

[Bennoel 10]

Most reproduction electrical switches I've had eventually give me trouble. Most right away.

 

[go-fish]

Myself and at least one other member just went through turn switch/brake light troubles.
I replaced mine with a repop and it has been working fine for the last 3-4 months since.

 

[Jeff Seighman]

Try twisting the socket in the housing, it might work. Ask me how I know.

 

[4mulas]

I’m sure you have already but really thoroughly check all your grounds. I’ve had similar issues but once I spent time really going through each connection and ground things came back to life. The switch itself could be somewhat faulty (give it a wiggle too)?

 

[Murray]

Make sure the taillight housing is grounded to the body.

 

[Kendog 170]

Run a test ground to bulb socket.
Also, some light switches come with an added ground terminal you can run to your dash/column ground

 

[Kern Dog]

Make sure the taillight housing is grounded to the body.

The 72 Duster uses a fully plastic taillamp housing. There is an external ground somewhere. The right lights up fine, I thought they shared a ground that attached to the trunk latch pillar.

 

[michiganpat]

had issues with my '76. this spring. My original turn signal switch had the latch that holds it on when turning right break off, so I replaced just the cam with a Dorman part (Dorman 49301), and started having issues with my taillights. after spending a day tracing wires/grounds, it was the replacement cam. Bit the bullet and bought a Standard Motor Products TW7 (the whole switch) and it's been working fine since.

 

[413]

You should look at a 64 wiring diagram.

He's working on a 72 duster. 64 is irrelevant to this man's car.

Just like the ball & trunion, tapered axle, and the single master cylinder.

 

[1WildRT]

As has been mentioned the tail/parking lights are a different filament from the turn/brake lights... So no that's not the T/S switch.. Check for 12v with a test light & check the ground..

 

[Kern Dog]

A lot of A body stuff carries over. I don’t know the details on the early A body cars but a lot of the 68-72 stuff is similar, 73-75 too.
1967 was a weird year with early and late stuff. 1976 had some one year only stuff related to emission controls.
I think I got this figured though.
1972 did have a few small unique things. The plastic housings used the external ground with a tab on the outer edges of the bulb socket.

This is the only year that I have seen that has this two wire terminal to a blue colored collar. Sort of weird.

Looking close, there is a tab to index the collar in the socket to get the bulb to make contact with the “contacts”.

If that collar is out of position, the bulb’s contacts won’t touch, no light. There are three indentations, two are for the pins on the side of the bulb housing, one is to index the collar.

I did have power to the wires.

The inside of the socket was cleaned with a Scotch Brite, the collar was put in properly and….

Now onto dealing with the dead gauge lights.
That is usually the headlight switch, right ?

 

[Kern Dog]

Before I close the book on the taillights, I wanted to check brake lights. Using my Douglas Fir assistant….

All four turn signals are working too. It’s almost like a new car now!

 

[413]

Dash lights is usually the dash lamp dimmer switch. You can bypass that dimmer switch and have the dash lights on full bright when lights are on.

 

[Kern Dog]

Dash lights is usually the dash lamp dimmer switch. You can bypass that dimmer switch and have the dash lights on full bright when lights are on.

Yeah? How is that done with a switch like this?

It is not like the B bodies that had a separate panel dimmer.

Everything is all in this switch.
I tried several other switches so far and can’t get dash lights from any of them.the fuses are fine. Dead bulbs in the dash ? All of them ? I wish that I could test these switches on a car that I know works with all the lights functioning.

 

[1WildRT]

How are you testing the fuses? Hopefully with your test light.... Probe the ends of the fuse holder, not the fuse... Pay no attention to what the fuse is labelled as, just check it for power at both ends... Some fuses are powered all the time.... Horn/brake lights/cigar lighter etc.... Some are only powered when the key is in the Acc or Run position... Turn signals fall in that category.... And one fuse only has power when the parking lights or headlights are on... That is the fuse for the dash lights... Check & let us know what you find...

 

[jos51700]

Probably not a factor here, but I've seen cheapie bulbs that don't have the contacts clocked correctly with the pins in the bulb base. Only one or the other will hit (or hit the wrong contact altogether).