Brake Light Problem
Thread Starter
8th Gear
Joined: Mar 2016
Posts: 8
Likes: 0
From: LaSalle Quebec
Brake Light Problem
I always thought that my brake lights were working properly until I parked in my driveway backwards . They work with the key in the off and on position but not when the motor is running for some reason . Any help would be a appreciated .
Pro
Joined: Nov 2016
Posts: 729
Likes: 118
From: Kelowna British Columbia
What if you jiggle ket in run position ? Weird that engine running would affect unless somebody has wired creatively. Use a test light and check at brake switch all 3 positions. Turnsignals and running lights work?
Melting Slicks
Joined: May 2015
Posts: 2,365
Likes: 428
From: Cape Girardeau Missouri
That's a strange one because the brake and hazard lights get their power direct from the battery (via their fuse) so they have power at ALL time.
The turn signal switch cuts off this constant power to the side the switch is moved but if that switch were faulty the brakes lights would never work.
Both the brake light switch and hazard switch are simple single-pole, single-throw switches that are impossible to wire improperly and either work or don't work.
This is a long shot but I suggest cleaning the rear lamp harness ground located near the radio antenna. VERY strange things happen when it is loose/dirty. Who knows? Maybe the rhythm of the engine and exhaust are causing a very marginal connection stop conducting altogether when the engine is running. In that vein I also suggest cleaning the lamp connectors.
Any signs that some really bad rewiring has been done?
The turn signal switch cuts off this constant power to the side the switch is moved but if that switch were faulty the brakes lights would never work.
Both the brake light switch and hazard switch are simple single-pole, single-throw switches that are impossible to wire improperly and either work or don't work.
This is a long shot but I suggest cleaning the rear lamp harness ground located near the radio antenna. VERY strange things happen when it is loose/dirty. Who knows? Maybe the rhythm of the engine and exhaust are causing a very marginal connection stop conducting altogether when the engine is running. In that vein I also suggest cleaning the lamp connectors.
Any signs that some really bad rewiring has been done?
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
Its not an electrical issue. When the engine is running, the brake booster is engaged. That brings the brake pedal up, ever so slightly.
Adjust your brake pedal switch under the dash. If you can do this in a dark garage you can monitor your brake light activation on the garage door reflection. You will be laying on your back.
Adjust your brake pedal switch under the dash. If you can do this in a dark garage you can monitor your brake light activation on the garage door reflection. You will be laying on your back.
Last edited by HeadsU.P.; Sep 3, 2019 at 07:35 PM.
