69 300 headlight dimming

[pmschmitt]

Have a 69 300 440 vert. When driving at night and I step on the brakes the headlights and interior lights dim. Last night I was driving with the heater on and the headlights cut out on me all together as did the rest of the lights in the car. I had been driving about 25 min. I cut off the heater turned the lights off then back on and had no problems for the next hour on the road until I got home.

What at could have caused this? I have read about bad alternators and loose battery wires etc,but my alternator is charging and I have good connection at both terminals. Any and all help is appreciated as usual.

 

[tallhair]

When you hit the brakes you're taking your foot of the gas so alternator RPM is reducing which cause the dimming. Something wrong in the charging system or possibly the battery

The heater's role in this story has me scratching my head unless it had nothing to do with it and your switch has some corrosion and the vibration made it get to a spot in the on spectrum where it lost connection and when you turned the head lights switch off and on you found a connection again.

 

[65sporty]

ck the alt output, yes its charging but may be putting out low amps. lights dim when hitting the brakes because your off the throttle and low voltage output at idle. heater causes a problem because its more load on the system

 

[pmschmitt]

Thanks for y'all's help