1974 Road Runner Tail Light Removal

[RR Fan Dan]

This may be a stupid question to some but I can't figure out how to remove the tail light from my newly acquired 1974 Road Runner. This started out as a bulb replacement because the brake light was not working. Replacing the bulb did not fix the issue. The tail light works but the dual filament for the brake light does not come on. I am figuring at this point it is a wiring issue and it appears the only way to access the wiring at the bulb socket is to remove the tail light assembly. I removed the 9/16 nut and the smaller screw under the bumper cover but the tail light is wedged in there with a tab and no way of dropping it down to clear the 9/16 stud that is holding it to the bumper. How is this thing removed?

 

[RR Fan Dan]

Okay never mind on the tail light. I figured that out. How do you get the bulb socket off?

 

[RR Fan Dan]

Okay, I'm not very good at electrical unless it is something obvious. I checked the wires and they all seem to be fine. The problem is in the left assembly. The right assembly works fine. There are only 3 wires going to the bulb socket. One black, One green, and one white. The white is soldered to the side of the bulb housing (assuming that's ground even though it is not black). The tail light works but the brake light does not. It doesn't make sense that one would work with out the other as there are only 2 wires so if the tail light comes on it is getting power. If it was the brake light switch the right side would not work.

 

[RR Fan Dan]

Okay I pulled up the wiring diagram for the car. The black wire operates the tail light. The green wire operates the brake light and turn signal. The turn signal works but not the brake light. The brake light on the right side works so I would think its not the brake switch.

 

[RR Fan Dan]

Okay I pulled up the wiring diagram for the car. The black wire operates the tail light. The green wire operates the brake light and turn signal. The turn signal works but not the brake light. The brake light on the right side works so I would think its not the brake switch.

There are two wires on the brake light switch. One goes to the fuse box the other operates both brake lights from what I can see.

 

[YY1]

Is the bulb oriented correctly in the socket?

Is it the proper bulb?

Are you sure both filaments are good?

Does the same thing happen when you put the bulb from the side that works, in the socket on the side that currently doesn't work?

Do you get 12v on the wire on the side that currently doesn't work when the brake pedal is depressed?

 

[72RoadrunnerGTX]

Turn signal switch. Do the four-way flashers work on all four corners? Never assume black wires are grounds on these cars.

 

[Nacho-RT74]

Black wire on tail light harness is parking lights circuit on 71/74s at least. Gray is ground when present.

 

[RR Fan Dan]

Is the bulb oriented correctly in the socket?

Is it the proper bulb?

Are you sure both filaments are good?

Does the same thing happen when you put the bulb from the side that works, in the socket on the side that currently doesn't work?

Do you get 12v on the wire on the side that currently doesn't work when the brake pedal is depressed?

Yes to all.

 

[RR Fan Dan]

Turn signal switch. Do the four-way flashers work on all four corners? Never assume black wires are grounds on these cars.

4 ways don't work at all.

 

[RR Fan Dan]

Does anybody have any idea what in the wide world of sports is going on here?

 

[72RoadrunnerGTX]

Do the turn signals work, specifically the left rear?

 

[RR Fan Dan]

Yes for the drivers side the turn signal works. But not the brake light On the passenger side both turn signal and brake lights work. That is why I am perplexed. It’s the same wire that operates the tun signal and brake light. So if the turn signal comes on then the brake light should come on too. I know the Brake switch is working and sending signal because the other brake light works. It’s really got me baffled.

 

[72RoadrunnerGTX]

If that's the case, again, its the turn signal switch. Brake pedal switch out goes to the turn signal switch. If the turn indicator works on that side but not the brake light its the T/S switch.

 

[RR Fan Dan]

Yes for the drivers side the turn signal works. But not the brake light On the passenger side both turn signal and brake lights work. That is why I am perplexed. It’s the same wire that operates the tun signal and brake light. So if the turn signal comes on then the brake light should come on too. I know the Brake switch is working and sending signal because the other brake light works. It’s really got me baffled.

And as a side note the 4 ways don’t work. I don’t know if they ever worked because I just bought the car Friday. The car was completely restored and has a current June 24 safety inspection sticker. I don’t know they missed a brake light. Previous owner said he was not aware of the brake light not working.

 

[72RoadrunnerGTX]

The 4-ways are also routed through T/S switch but have a separate flasher and power supply that will need troubleshooting to verify if that issue is related to the T/S switch as well.

 

[RR Fan Dan]

The 4-ways are also routed through T/S switch but have a separate flasher and power supply that will need troubleshooting to verify if that issue is related to the T/S switch as well.

Well thanks for that. I guess it’s off to hunting for the turn signal switch. I assume it’s under the dash somewhere. Probably could follow the brake switch wire at the pedal and find it. I just assumed since the switch was sending signal to the other brake light that the switch was working. I guess the switch sends a left and right signal for the brakes and the left signal is broken.

 

[72RoadrunnerGTX]

The turn signal switch is at the top of the steering column, its connector is accessible at the bottom of the column. Yes, you will find the other end of the switched brake light wire there. Careful with cheap repo replacement T/S switches, total junk.

 

[RR Fan Dan]

The turn signal switch is at the top of the steering column, its connector is accessible at the bottom of the column. Yes, you will find the other end of the switched brake light wire there. Careful with cheap repo replacement T/S switches, total junk.

Thanks. I’ll hunt for it tomorrow

 

[YY1]

I agree, I think we're at checking or at least inspecting the turn signal switch.