HEADLIGHTS FLASHING/PUSLING

[Dan]

67 Ranger, all lights function properly, but when the headlights are on, and in particular at slower speeds, the headlights begin to pulse, so much so it almost looks like I am trying to intentionally get the attention of the driver in front of me.

I'm sure there's a simple solution to this but I am no expert on electrical, can anyone tell me what to go after? Alternator did get replaced but it was years ago and the truck had sat for many of those years if it matters any.

Thanks!

[HIO Silver]

According to many sources I have read, it is usually caused by an old voltage regulator.

Are your lights weak and really yellow?

[1972hiboy]

Sounds like your headlight switch breaker is tripping and re-setting. I had this happen to my truck when I had the camper on it. turns out my camper marker lights were overheating my headlight switch. Do you have any extra electrical loads on the truck, wiring? could try a new headlight switch if yours is old and questionable.

[69Ford]

One of the problems is these trucks were never designed to handle the load of modern headlights (halogen). Burns up switches and causes the breaker to trip. LMC sells a wiring harness to fix this (and other sources) Uses relays and power directly off the battery. Real easy to install and you do not have to splice into your harness. Also what's nice is there is a relay for both high and low beam so if one fails you still have headlights. I think there is a right up somewhere on this site to make your own.

[Dan]

Thanks, I can check out those options, I also didn't know about the LMC harness, I'll look into that too, I get parts from them frequently, thanks for the tip!

No extra lighting on my truck at all, not even a radio (factory AM radio never worked). Just the basics. Thanks again!

[390bump]

Change radio station from disco channel...

[Dan]

Or I could just repaint it like a Sheriff's vehicle and save the cost of installing the wig-wag police lighting option!

[Mach428]

From your post it sounds like they only flash while the engine is running? If so, it's most likely a chargin issue. I had the same thing with my 69 Mustang and found the problem to be in the VR AND the grounding.

[Nitekruizer]

If the pulsing gets faster with engine RPM or goes away with higher engine RPM, it is definitely in the charging system.

Before replacing the VR, I suggest checking the VR to make sure it is grounded. Some people say that it's also a good idea to have a Ground Strap between the engine and body. Personally, I've never had an issue from not having one, but it may be worth a try if your problem persists.

I would also check (test) the alternator's diodes. Not that difficult to do, in fact, you can usually do it without having to take the alternator apart. You just need access to the "BAT" terminal, the "STA" terminal and ground. The alternator does have to be disconnected though.