Head Lights dimming

I have been driving my 2009 5.7 LX hemi swapped 73 RR for a few months and must say, I love driving again!! Lately I have found headlights are “surging” or dimming in time with the engine as it hunts a little up and down at idle... it’s not hunting bad just like the alternator is kicking on or off or something.

My headlights are set to a common ground on the subframe, and are wired directly to the main battery stud post on the firewall. (I have a trunk mounted battery with 0 gauge feeding it.) with high and low beam relays fed from the switch.

I have noticed the tail lights are doing it to.

The voltage at the battery is 14.5-15 consistently, it never drops below 14.5

At the main supply post it’s 14.25-14.75
And at the headlight relay it’s staying between 13.96-14.5

It doesn’t seem to be an alternator issued but it is time with the engine. And it does it with or without the fans running.

Any thoughts?

Do you have access to an oscilloscope? I'd scope the alternator output.. Might have a diode failing..

1 Wild R/T said:

Do you have access to an oscilloscope? I'd scope the alternator output.. Might have a diode failing..

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I know a guy with access to one! I may see if he wants to bring it next time he comes back this way! I would assume he would know what to look for?

You hook up the the output stud & watch the wave form.... Diodes should only allow half a wave, anything reversing is a problem...

check the alt ground. maybe you run a temporary ground from alt to engine-engine to body to see if it changes ?

vance.dykes said:

check the alt ground. maybe you run a temporary ground from alt to engine-engine to body to see if it changes ?

Click to expand...

do you have enough alternator amps for your power needs? do you have the crackedback headlight harness system that helps with that issue?he is on this forum just look up crackedback under members.