I've noticed this happening a few times over the past year or so and I'd like to get it fixed.

While driving to work this morning I could feel a light thump in my truck along with my lights going slightly dim for maybe 1/4 of a second. It continually did this for about 10 minutes until my brake and abs lights came on, then it all stopped. I can turn my truck off then restart it and all is well again. Seems it only does this during cold weather or when we get a lot of rain. Brakes seem to work just fine but have not checked the abs by locking up the brakes. Does anyone know what might be causing this? I was thinking maybe there's a relay or valve that's sticking but I don't know that much about the brake systems on these things.

 

doubt its your brakes. sounds like an alternator or battery problem.

 

Is the "thump" what you refer to as a pulsating noise? I'm a bit confused here.

I agree with Feejay that you have a different problem, but that doesn't rule out the possibility of 2 problems occuring at once.

 

My battery and alternator are fine. The noise I am referring too is more of a "wump" and happens about every 4-5 seconds until the lights come on then it stops. It almost sounds like the abs valve/unit is cycling. If this were a battery or alternator problem, it would be occuring a lot more frequently and like I said before, this happens to me when it gets cold or there's lots of moisture in the air.