Hi,

Recently, I have been noticing a pulse in my headlights and interior lights while the engine is on. When I turn the engine off and turn the lights on automatically, I see no pulsing. My aftermarket radio has no pulsing. It's more noticable on my instrument gauges and headlights. It's a bit hard to tell if it's rpm dependent as the audio cues throw me off a bit, but it seems like it is.

It's very feint and barely noticeable though If I was to point it out at night, my wife would notice it. I had the alternator checked and it shows good voltage though I'm starting to suspect the voltage regulator within the alternator.

Is there a way to test the regulator? Is the symptoms I described indicative of another problem all together?

Thanks in advance.

 

It sounds like a bad ground somewhere in your lighting system.
On my 01 blazer it was exactly as you describe and it ended up being a rusted through ground wire in the back end under the truck near the tail lights.

I've included a pair of pictures from this repair to my own truck. The ground wire from the harness to the frame was the culprit.

 

I'll have to take a look. Did your truck still pulse off of battery or just with the engine on?

I'm having trouble understanding how this could cause a pulse in the lights only with the engine on. When I run the lights just on battery, I have no pulse.

Thanks again. I'm going to go take a look tomorrow.

 

Mine only gave the pulse with the engine on as well. Incorrect grounding can give all kinds of problems that you wouldn't expect.

BTW, your truck may not have the fault in the exact same place as mine but it is most definitely a bad ground somewhere. Because of the flickering you mentioned with the headlights on only it will probably be either in the harness or connections to the tail lights or a ground to the headlights themselves.

The tail light harness under the truck is just the most likely spot as it is the most exposed to the elements and easiest to get damaged.

Good luck.

 

Will do. Thanks for the help. I'll be back tomorrow with an update.

 

My headlights have been flickering as well, HID kit exaggerated the issue. Let me know what you find out.

 

I have yet to check the grounds as it was crazy cold for my area this morning.

I have been checking on other things that may cause the pulsing which I will check based on price to troubleshoot.

1. The bad ground that I will check at my earliest convenience.

2. The internal voltage regulator in the alternator is going out.

3. The belt is slipping and not squealing thus the constant and pulsing voltage drop.

I'm going to check each one till this checks out in order. Will keep you guys updated.

 

Not sure if this is the cause, my dimmer switch on the dash gets real hot on my 97. If i adjust this when I see the flicker it goes away, for a while that is. Since I pulled the fuse on the interior lights I have not had this issue. I am thinking my problem is the dimmer switch, mabe yours too?? Just something to look at, I am no expert.

 

Wow, thanks! I'll be sure to check you guys out when my diesel Jimmy needs a fuel injection nozzle!

 

my 2002 pulses as well it's a V-8 swap I couldn't figure this out thanks for the info I suspected it was a ground I am definatly checking the grounds asap.