Lights intermittently brighten then go back to normal
 

Driving home last night my headlights and instrument panel would get signifantly brighter for a minute or three and then go back to normal. Of course it's possible that they dim for long periods and then go back to normal for a short period...:) I have recently started driving the car again after a few years so I don't remember how bright they were before.
My first thought was that the voltage regulator is about to die so I need a new alternator....


Thoughts and suggestions please.



1972 Luxury Lemans.

Most of the time, automotive electrical problems can be traced to bad grounds. Check the ground connections on your headlights - remove the screws, clean up any rust or corrosion on the terminal as well as where they bolt to the body, and reinstall.

Not sure that would affect instrument panel though.

You need to do a voltage check with lights on and other loads to see what the charging system is like before jumping into Guesses.

I'd blame the voltage regulator if you see this problem with both the headlights AND the instrument lighting at the same time.

You say your voltage regulator is about to die, so you need a new alternator. Doesn't your car have an external voltage regulator on the firewall as opposed to an internal regulator in the alternator?

I'm asking not saying and no the voltage regulator is inside the aternator.

Voltage at idle with the lights on (my only used load) is 14.45VDC


The problem only presents itself while driving.

Wire in a voltmeter inside and watch it when this happens, or have someone else watch it. Something has to be switching on and off
or higher and lower to get headlamps to flicker like that. Maybe even bad contacts in the headlamp switch or dimmer switch. You
could also do a wiggle test on switches with headlamps on ( would have to be dark) to see if anything goes dim. nWiggle wires at switches.

^^^^ the voltmeter will tell you if the alternator/regulator is working correctly. Check the alternator belt also.

George

It started to act goofy even at an idle. I put my Fluke on it at the battery and read a low of 14.3vdc and a high of 18.6vdc when the lights got bright.


Decided to change the alternator today since I was going to be resealing my power steering pump. I'll post back to give results Tuesday night after work.

It was the voltage regulator
 

Drove 40 miles home last night and not one variance in the brightness of my lights. The new alternator took care of the issue.

Good to hear, the voltage variance was the the answer to the question. Voltage regulator issue.