Brake light fuses began to blow out of no where a month ago. Auto shop has disconnected 3rd brake light mounted on deck lid. Not the problem.

Tiny
BLAIR1947
  • MEMBER
  • 2003 CADILLAC DEVILLE
  • V6
  • 2WD
  • AUTOMATIC
  • 35,000 MILES
Brake light fuses blow 3-5 days after I put in a new one. Auto shop can not find problem. This began suddenly about a month ago. SERVICE ELECTRICAL SYSTEM light comes on alerting me the fuse has blown again. Alternator checked out OK.
Do you
have the same problem?
Yes
No
Saturday, August 1st, 2015 AT 8:29 AM

1 Reply

Tiny
CARADIODOC
  • EXPERT
A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a 12 volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it's not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.

For intermittent problems like yours the bulb may be dim already. Watch what takes place when it gets bright. That's when the short is occurring. It could be due to the rocking of the engine when you shift between reverse and drive. It could be due to the body flexing when you drive over bumps in the road. The bulb limits current to a safe value when the short occurs, in this case about one amp. If the brake lights aren't bright enough with a brake light bulb replacing the fuse, try a headlight bulb. The low beam filament will limit current to five amps, and the high beam filament will allow about six amps to flow. That will pass enough current to make the brake lights on the back of the car visible.
Was this
answer
helpful?
Yes
No
+1
Saturday, August 1st, 2015 AT 10:35 PM

Please login or register to post a reply.

Recommended Guides