Topic: Headlights dim and pulse - 68

[68 GT]

The headlights on my 68 coupe are not very bright and they kinda pulse brighter to dimmer while driving at night. I believe they do this no matter if I have them dimmed or not dimmed with my dimmer push button foot switch. I believe my blower motor also speeds up and slows down a bit when I have the blower on high. Has anyone else experienced these problems? What headlights are people using in their 68 Mustangs?

Thank you for any advice and guidance.

[ruppstang]

It sounds like a voltage regulator problem. The originals used points, and they could cause the pulsing. New ones are solid state and are less problematic. To keep the original appearance, you can move the old cap to the new one.
On a driven car I have used Halogen headlights. If you use them, it is best to replace the headlight switch as they draw more current.

[midlife]

It sounds like a voltage regulator problem. The originals used points, and they could cause the pulsing. New ones are solid state and are less problematic. To keep the original appearance, you can move the old cap to the new one.
On a driven car I have used Halogen headlights. If you use them, it is best to replace the headlight switch as they draw more current.

If using halogen headlights, best to run them off a relay system, as any of the stock headlight switches can't handle the power that halogen lamps draw.  Lots of kits out there for headlight relays.

[68 GT]

Thanks for the replies! Maybe In should try a relay in my lighting circuit. I installed a new headlight switch, probably back in 1990, when I got the car on the road following restoration. Any suggestions for a headlight relay brand? Silly question, where/how do you wire it in?

How about my blower motor speeding up and slowing down a bit? Possibly replacing the voltage regulator would cure that?

Thanks again!

[68 GT]

Oh, pretty sure my headlights are halogens, forgot to state that in my last reply.🙃

[midlife]

Halogen lights will definitely trip the internal circuit breaker in the headlight switch.  A relay is your best bet (but of course, it isn't concours correct).  Rocketman Classic Cougar Innovations makes relays and has a great reputation.

[68 GT]

Thank you Midlife!! Seems like a good winter project on the 68!

[67350#1242]

Agree the pulsing voltage is the regulator, as different resistors are mechanically switched in and out, which "steps" the charging current up or down.  Solid state regulator uses a transistor that acts like a variable resistor and "ramps" the charging current up or down, so no noticeable jumps.
Your blower motor speeding up and down as well as head/interior light flicker both caused by the mechanical regulator.

[68 GT]

Sure do appreciate your guys responses! Maybe I should replace the headlight switch, install a relay(sure hope they come with good instructions) and install a solid state voltage regulator. So?do I remove the voltage regulator in the engine compartment? I?m confused on how to install and wire in the relay and solid state voltage regulator. Maybe this conversation/advice should be communicated through a personal message or email?

[ruppstang]

The voltage regulator is as simple as purchasing a new one and plugging it in place of the old one. The light relay is the best fix unless you want to keep your car concourse. I have replaced my old switches with new ones and have driven hundreds of miles with halogen lights with no issues.

[68 GT]

Okay, so the voltage regulator in the engine compartment are solid state? Just replace it with one just like it? And I should replace the headlight switch with new, correct? If a headlight replay is the cure for pulsing headlights, I?ll do it!

[ruppstang]

Go back and read 67350#1242's reply in post above, he explained your problem very well.

[jwc66k]

Oh, pretty sure my headlights are halogens, forgot to state that in my last reply.🙃

If you drive a lot (yes, it is two words) at night, halogen bulbs are nice, but 56 year old wiring and associated components were not designed for them. You could "solve" your problem with incandescent headlights.
Jim

[67350#1242]

I have heard somewhere that the C9 marked headlight switches will handle most halogen headlights, as they were designed for a 4 - lamp system, and have a heavier thermal breaker than the earlier 2-lamp.  Also most service and aftermarket headlamp switches will most likely work.  I have also run halogens on several cars without problems.

OP please note:  There are 2 distinct problems that can arise.  The first, which you describe is just a subtle flicker or brightness fluctuation in all bulbs, as well as the blower fan, etc.  This is a regulator problem.

The second problem is headlights completely shutting off intermittently, then back on.  This is caused by an automatic reset thermal circuit breaker built into the headlight switch.  Installing halogen bulbs will sometimes cause this problem because they typically draw more current.

If I were you, I would install the halogen bulbs and try leaving them on for a period of time.  You may not need to do anything with the switch, but if the problem exhibits installing new one should fix it.