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Discussion Starter #1
Here's a new one on me. A friends 08 brake lights are on all the time, checked all switches and they are working correctly. Tried swapping relays to no avail. Here's the wierd part I cannot track in the schematics, when the tail light relay is pulled the brake lights now function as they should, replace the relay and the brake lights are back on. Tried replacing the tail relay and same problem.

No trailer hitch, only added accessories are a Kury lighted mudflap and OEM spoiler.

Any ideas?
 

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Color me corn-fused. The tail relay provides power to all the rear lights. If you removed it, none of the rear lights should work at all, along with the meter panel. If the lights work with the tail relay removed, you have a short providing power to the tail light circuit, bypassing the relay.
 

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GL1800 Doctor
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A shorted bulb filament can cause this. The tail light filament is touching the brake light filament in one of the bulbs and giving the brake lights power when they should be off. Pulling the tail light relay removes the back feeding power from the brake light circuit. It's rare but does happen.
 

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A shorted bulb filament can cause this. The tail light filament is touching the brake light filament in one of the bulbs and giving the brake lights power when they should be off. Pulling the tail light relay removes the back feeding power from the brake light circuit. It's rare but does happen.
Great catch Rob, I would have missed that one.
 

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Discussion Starter #6
Thanks guys
I am going to disconnect the extra lights first to see where the PO connected them, if that shows nothing then we'll start pulling bulbs one at a time.
 

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GL1800 Doctor
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Thanks guys
I am going to disconnect the extra lights first to see where the PO connected them, if that shows nothing then we'll start pulling bulbs one at a time.
If the extra lights are hooked up to be running lights and get brighter as brake lights, then there might be a steering/blocking diode that has shorted in those lights.
 
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