lights dim when pressing the brake

[djjamin]

maybe someone can help me out with this. whenever i press the brakes theres a squealing sound coming from the engine bay and the lights on the dash start to dim. now i have some idea of what the problem could be. Had to take out the head unit to fix it and i noticed the previous owner made it a HUGE mess in there, couldnt find where it was grounded to, but i disregarded it because i got my radio working again lol :icon_bigg; i just assumed all was well in there. I have a feeling that the head unit is not properly grounded which is cause the problem not only with the brakes but the head unit shuts down when i put the volume at a certain level.

I have a 89 auto btw

Any help would be greatly appreciated.

 

[RazoE]

All my supras and friends' supras dim when you brake, guess it's old grounds?

 

[MKIIISupraGuy]

You could run a ground wire from the outer metal shell of the radio, to either the firewall, or the metal brace the dash bolts to.

 

[hvyman]

Wiring or alternator issue.

No dimming here.

 

[djjamin]

Wiring or alternator issue.

No dimming here.

The alternator was my second guess. Grounded my head unit, and that didnt do anything. Turns out the bass settings were too high that when it reaches a certain volume it shuts down. From what i can tell, when in either reverse or drive, while holding the brakes i hear a squealing noise from the alternator. Im hoping its just the belt or something, although my other guesses are that its the pulley or a bearing.

 

[hvyman]

If the belts not tight it will squeal and and not produce enough voltage out of it. Lights load up the car. ESp at night with the headlights on and heater and radio.