1971 Cougar tail light problems

1971 Mercury Cougar

So I ordered and received the complete reworked tail light housing and plugged them into the car. I have Tail lights, and Reverse lights. But brake Lights only on the Drivers Side, and Hazard Lights only on the drivers side.

I checked the ground in the trunk, when I removed it, all the bulbs would glow real dim on both side "With the brakes on,. When i hooked the ground again, the passenger side went out, and the drivers side works.

I have no blinkers at all with neither the original sequential box in the fender, or the the new digital one I bought. When I turn on the hazards, the drivers side works great, sequencing perfectly, but nothing on the passenger side.

Both housings and sockets were refurbished, and the bulbs went in great. and when I turn on the head lights, they both work perfectly. I also have replaced the Blinker Switch as well.

Any ideas?

Hey Greg, below is a good link to start with troubleshooting, others may chime in with their own experiences.
Quick question, what problems were you having before you changed out the housings and other parts, the same?
And just to verify your using the old incandescent (1157 bulbs and similar) not the newer led plasma


Sorry so long. Yes, I have replaced the blinker switch, rear housing and sockets, sequential box in trunk, and flasher can and the problem remains the same. Yes, I have new bulbs, not led plasma.

The good news is you don’t need to buy any more unnecessary parts. You need to troubleshoot and find out why it doesn’t work. Likely you don’t have power or ground someplace where it should be. Light bulbs need those two things. You will need a multimeter and to read the troubleshooting guide.

Your copy of the factory shop manual has the turn signal wiring diagram, as well as all other wiring diagrams for your car.

JMHO but I think advice saying which manual to look at should also include a page number. It would help eliminate confusion if someone looks at the wrong diagram.

So I now have tail lights, hazards, brake lights, but still no blinkers. The left blinker light come on steady in the dash when the blinker is turned to the left, and when it is in the middle. When the blinker on turned to the right, the signal light goes off. I have replaced the blinker switch, but i don’t think it was the problem before. With the Key off, I have one hot wire to the plug. When the key is on, I have 2 hot wires.

I don’t know if the one hot wire is there for the hazards only, or if it also feeds the blinker switch. I wish I knew how many wires, and what colors were supposed to be hot at the plug. I can’t seem to find any way to figure this part out. I know I’m close, but still not quite there.

Any advise would be appreciated.


So here I am again still baffled by my turn signals for my 1971 Cougar…

I have replaced the Pigtail which plugs into the turn signal switch. I replaced the Switch, but noticed they said it might not handle the load of bulbs, VS LED’s. I have running light, tail lights, Hazard Lights, but no Light’s at all when I depress the Blinker. The Trouble shooting guide says if I have no turn signal lights but do have Hazard lights, the switch is probably bad.

But I’m using a brand new switch.

My question is, could this NEW turn signal switch be bad? Below is the notice for the product I used.

“This offshore switch is assembled with plated steel rivet contacts as opposed to brass rivet contacts like original. Whereas the Torino or Mustang do fine with 2 incandescent rear bulbs the Cougars with 6 bulbs put too much load on the switch and they fail. The only way these switches will hold up in a Cougar is if you convert to LED. We are hoping the supplier will take our advice and correct this problem but until such time we cannot warranty this product. Don Rush 9-11-2017
1970-72 Drake Turn Signal Switch Brake Circuit Analysis by Vic Varberry”

I plan on switching to all LEDs as soon as I can find some LEDs. Is this switch already destroyed? Or is it just not able to complete a circuit to bring power to the Sequential unit in the trunk.

I wish I could talk to Vic for just 5 minutes, but can’t seem to find a contact for him.

Can anyone help with this?

I restored a 72 xr7 a few years back and was having what appeared to be demons in the rear taillights….restored housing…sockets and reworked wiring that had been bench tested…along with a new Ts switch. After much dismay and inappropriate use of the English language…it turned out to be a tang on one of the terminals that I had evidently removed before fully released from the turn signal switch plug and had jammed in the plug is a way to connect two adjacent wires….I remember how happy I was to discover it…how long I had looked for the culprit and how I was unable to blame it on anybody else but me.

I was worried about the pins on the car side, someone had soldered a broken wire right at the plug. I thought there might be a bad pin So I bought a new plug pigtail all together ans spliced it in. Still, everything but the turn signals work. The trouble shooting guide says all the power comes through the emergency switch. I just cant figure out why there is power to the emergency, running and brake lights, no power to the tail light from the blinker switch.

I’m past the cussing now, starting to go to tears:)

Hey Greg, I feel your pain. Sorry I can’t offer you any good advice on your trouble shooting dilemma. But since you mentioned switching to LED’s watch the below video, then see if you can get in touch with Richard at WCCC for some help with your issues and upgrade possibilities. To answer one of your other questions, yes I believe many of us have received bad new parts from different sources at one time or another. :smoke: