87Chief Posted December 20, 2010 Share Posted December 20, 2010 As the title says... I was driving tonight and whenever I hit the brake pedal... I noticed my headlights dimmed, and if I opened the door, and pushed the brakes on, interior lights dim also... Any opinions? Link to comment Share on other sites More sharing options...
mvusse Posted December 20, 2010 Share Posted December 20, 2010 Weak alternator has trouble with the extra load of the brake lights would be my guess. Link to comment Share on other sites More sharing options...
kyleag89 Posted December 20, 2010 Share Posted December 20, 2010 My truck does this too but not too noticeable, and I have a new alternator. I like to blame it on 21 year old wiring. Link to comment Share on other sites More sharing options...
TrailReadyMJ Posted December 20, 2010 Share Posted December 20, 2010 I have the same problem, and right now I blame the alternator. When I first got it, it was REAL bad, and the lights would dim to ~50% at idle with the brakes on, and brighten back up to say 80% when the brake was off. Above idle the lights would be fine, but if I tapped the brake, they would dim a bit. I swapped in a USED alternator I had lying around, and it greatly helped the problem! However, the lights do still dim a bit at idle with the brakes on. I have a 105A alternator in known good condition sitting in my garage. I will try to swap it soon and post up with results. I want to note that I have gone through and checked/cleaned a bunch of grounds and power connections, ran new battery cables, new clamps, Optima red top, extra ground straps, etc... etc... so I'm pretty sure the rest of the system is in tact. It was a nightmare when I got it though! Link to comment Share on other sites More sharing options...
jimoshel Posted December 20, 2010 Share Posted December 20, 2010 A short in the brake circuit wiring, Either in the switch, the light sockets or the wiring. If the alternator was weak the battery would carry the load. Until it died. Weak alternators won't keep a battery charged. If it has a trailer connector would be the first place I'd look. Link to comment Share on other sites More sharing options...
87Chief Posted February 22, 2012 Author Share Posted February 22, 2012 It does have a trailer connector. Should I check to see if there is a short from connector to the brakes? Link to comment Share on other sites More sharing options...
cruiser54 Posted February 22, 2012 Share Posted February 22, 2012 It does have a trailer connector. Should I check to see if there is a short from connector to the brakes? Check that and also remove the braided strap from the firewall, scrape the paint off from undeerneath it, clean the terminal and reinstall. Link to comment Share on other sites More sharing options...
JeffN Posted February 22, 2012 Share Posted February 22, 2012 Ground problem, check the grounds from the battery to the body and from the body to the engine Link to comment Share on other sites More sharing options...
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