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Discussion Starter #1
The most recent problem on my 87 Sundance involves the tail lights.

With the running lights off, the rear brake and turn lamps work normally.

With the running lights and/or headlights on, I have the following problems:

  • The tail lamps all light up, except when I apply the brakes, in which case the right brake lamp goes out. The high brake light functions normally.
  • Turn signals remain solid (no flashing)

The back-up lamps and front running lights/turn lights are unaffected, though one of the backup lights is much brighter than the other, despite both having identical new bulbs installed.

Any thoughts on how to trouble-shoot this electrical gremlin? The fuses are all intact, and the bulbs are all the correct type.
 

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Bad socket grounds. We used to replace the brass ground terminal in the sockets instead of replacing the whole socket. You may be able to spot solder a ground wire to the outer socket shell and splice it to the existing black ground wire for a good connection.
 

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Discussion Starter #3
Hmm, grounds eh? I cleaned all the grounds under the hood a few months ago. Is there a main ground strap for the tail lights? If so, where is it likely to be?
 

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It's the grounds at the socket bulb holders themselves. If you jump a ground wire to the socket shell, you should notice a brighter bulb and a return to flashing turn signals.
 

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Discussion Starter #5
IC: I did as you suggested, and my lights are indeed working properly and have returned to their previous brightness. Thanks for your help!
 

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Discussion Starter #6
Ok, now my high brake lights are not turning on. I have replaced the bulbs and checked the wiring at the connectors and all seems well. All the fuses look good too. What is the next thing I shoulf check? All other lights are functioning correctly.
 

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Check to see if you're actually getting voltage at the socket first, and if you aren't, check for continuity between the brake light switch terminal and the CHMSL. This will make sure you don't have a break somewhere you can't see, like under the carpet. If the bulb is good and the wires check out (make sure to check power and ground), the switch is a likely culprit.
 
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