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Discussion Starter #1
Got the gas tank replaced and new leaf springs on the old girl. Now a new issue has cropped up. The other night my wife came home and noticed the brake lights were on. Tried to pull the pedal up but the lights still stayed on. So she disconnected the pigtails from the tail lights and of course the lights went out. Looks like a new stop light switch is needed. No problem.

Fast forward to yesterday. Switch replaced. Put the pigtails back on. No brake lights. Put the lights on. No tail lights. Rotate the pigtails and the tail lights come on but no turn signals or brake lights. Not sure what to do at this point. The pigtails looks like they were replaced at one point since they are both spliced into the original wiring but still look very old, like originals.

Any thoughts? We were very careful replacing the stop light switch so I do not believe any other wires came loose. Maybe the pigtails are corroded and need to be replaced?
 

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First, we need to know if any 12V power is getting TO the pigtails.
 

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Yeah, I have this problem alot on my 1966 Coupe. I don't know if it's because I have the original taillight housings and reproduction wiring, or what. What I do to get them working properly is put the headlights on, put car in ACC and put the turn signal on. Then I go back, and push and twist at the pigtail till both are working, than I try the brake light. It's really stupid, but it works.
 

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Yeah, I have this problem a lot on my 1966 Coupe. I don't know if it's because I have the original taillight housings and reproduction wiring, or what. What I do to get them working properly is put the headlights on, put car in ACC and put the turn signal on. Then I go back, and push and twist at the pigtail till both are working, then I try the brake light. It's really stupid, but it works.
Two different sources. The taillights get 12V, and the brake/turns get 12V. If his new brake light switch, or the turn signal switch, are crap, then he's wasting his time screwing around with the plugs in the trunk.
 

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Discussion Starter #8
Two different sources. The taillights get 12V, and the brake/turns get 12V. If his new brake light switch, or the turn signal switch, are crap, then he's wasting his time screwing around with the plugs in the trunk.

So try to take a voltage reading on inside of the plug with the lights on? The weird thing is that the turn signals were working the other day when I was starting to troubleshoot this.
 

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Yeah. Notice Ford only used those weird plugs for about 18 months? For a reason.
 

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I've had problems a few times with the springs in those brake switches. Get in the car and work the switch manually while someone watches the light for you.
 

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Two different sources. The taillights get 12V, and the brake/turns get 12V. If his new brake light switch, or the turn signal switch, are crap, then he's wasting his time screwing around with the plugs in the trunk.
I tested mine to make sure they were getting 12v, and both of them were. It has to be those stupid plugs that Ford used. Is there any way to upgrade them? I'm tired of having to fix my taillights everytime I drive the car (which is just about everyday because it's my daily driver).
 

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IMO you had a 'sweet spot' situation before you moved anything. Bad grounds are so common on the taillights. I would take it all apart and clean every contact and start trouble shooting if you still have a problem.
 

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Discussion Starter #13
Ok maybe I'm daft. This might be a stupid question but where do I measure the voltage on the pigtail? I do not seem to be getting 12volts but I am trying to measure positive from the copper plate that surrounds the inner rubber plug and placing the ground on the taillight housing. Is this correct? The reason I am confused is that if I rotate the pigtail around the housing connector I do get lights kinda. Sorry in advance if this is really stupid.
 

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I don't think so by your description. The 'copper cup' or 'plate' is neg. The smaller 'post' is pos. FWIW I still think you have a bad ground. I experienced almost exactly the same symptoms and after cleaning all the contact point with steel wool I was back in business.
 

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Discussion Starter #16
I don't think so by your description. The 'copper cup' or 'plate' is neg. The smaller 'post' is pos. FWIW I still think you have a bad ground. I experienced almost exactly the same symptoms and after cleaning all the contact point with steel wool I was back in business.
Ah... Thank you very much, that really helps. I went and bought a test light and used that instead of my Fluke.

I attached the ground strap to the housing and inserted the probe into the hole in the center of the pigtail and presto it lights up when the light-switch is engaged so I got 12v verified coming from the light-switch on both pigtails.

But with the light switch turned off and the brake pedal depressed my probe does not light up. That might be a separate issue though. "Adjustments" were made before and after replacing the stop light switch so that may be out of wack. I will give your tip a try and clean all contacts with steel wool. Thanks again.
 

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Remember that you're grinding through the taillight housing to the body. It might help to run a jumper from the bezel mounting point to the frame with a good clean connection (either for testing purposes or as a solution)
 

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Discussion Starter #18 (Edited)
Ok, so far here is what I have found using a test light. The smaller center hole in the pig tail is the 12v for the taillight from the headlight switch. The copper plate on the outside of the barrel within the pigtail is the turn light and brake light. I've got light on both so it definitely looks like a grounding issue with the housing. Hopefully I get some time Sunday to go through and clean everything real good.

Also toying with the idea of ditching the pigtails and just using a universal tail light socket to convert to 3 wire and just forgot about the whole housing/ground thing, seems to be a real pain in the ***. Anybody do that before? I figure have dremel will travel.
 

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Discussion Starter #19
Fixed! Well at least one side. Tail light on both, brake and signal on the left. Followed Black65's advice and scrubbed everything with steel wool. More than half way there. The bulb sits a little loose in the right housing. Spring might be getting worn. Hoping I do not have to replace the housing since I have not really heard great things about the repro's.
 

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Discussion Starter #20
Now both are fixed. Thanks to all who were kind enough and patient enough to answer Newbie questions. Also got a new tool out of it. Test lights are indispensable when troubleshooting these kind of issues and seem to make isolation easier. Thanks again all. :content:
 
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