Pulsating lights

[ddarnell]

Returning from a long trip Sunday, I noticed all the lights on the vehicle pulsating.
Voltage regulator?

[04 Diesel]

My 76 will do the same thing, I can only see it sometimes when the truck is ideling.

[Desoto61]

Most likely candidate, but do you have any other larger electrical loads running at the same time, especially something intermittent like a stereo? Was this at idle, did it go away at higher speeds? If at idle is the idle steady?

By that point I thought most of them were solid state so it's not as common as on the older thermal/mechanical regulators.

[ddarnell]

I noticed the pulsating at cruise speed as well as idle. No other loads. I did recently replace the headlight switch but it seems unlikely that would be the culprit.

[Desoto61]

Do you have AC or electric fans? How fast were the lights pulsing?

Obviously the best option would be to see if you can re-create it and throw a voltage meter on it to see what's happening. You could always turn on the headlights with the truck off for a while and see if it pulses, that would eliminate the voltage regulator or alternator as a culprit and just test the switch. You can always connect up a battery charger if you were worried about draining the battery.

If the lights are pulsing but the battery voltage seems steady it points to your lights. Most of the older style switches have an internal thermal breaker, it is possible that breaker is causing those issues, but at this point I would guess voltage regulator since it's not happening under a set condition.

[ddarnell]

No AC and just the blower motor. Great advise, I'll check it with the engine off.....hadn't thought of that.

[Steve G]

Check this out, lots of good info.


http://www.dieseltruckresource.com/f...solved-317745/

[KRB64]

What vehicle?

Could be a poor ground or a bad spot in a wire. Ask me how I know...