I took the car out for its first time night time driving last night - I drive through a section of road where the high beam is absolutely needed. After having the high beam on for a few minutes, all lights started flickering. Once I switched to the low beam, the flicker went away. I got home, had the car running and when I turned on the high beam after a few seconds all four lights started flickering - non uniform, fast flicker. Turn the high beam off and everything goes to normal (2 outer lights work as expected). Search shows the dimmer switch or a relay as the most probable cause?

Any other thoughts appreciated.

 

It could be a ground problem, not uncommon in our fiberglass cars. It could also be the regulator in the alternator. When you put more load on it with all 4 high beams on, it could trigger the issue.

Mike

 

The headlight switch has a built-in circuit breaker-

which could be causing the flicker-

Especially since at idle the flicker was "different."

To cure-check the grounds as V2 said and look at cleaning the contacts on the bulb and connectors as well.

Richard

 

It could be a bad connection inside of the headlight switch plug. Headlight bulbs draw a high amperage and that causes a lot of heat in the plug which loosens the connections and causes further heat. It's very common to see the plugs partially melted from the heat. It could also be a charging problem causing the flicker. To see if it is manually open your headlights using the vacuum override switch then start your engine, turn your headlights ON until the flicker starts, then shut your engine OFF and see if the flicker continues. If the flicker stops it could be a failing voltage regulator or a diode in the rectifier; both easily fixed for little expense.

 

If the lamps are flashing in unison completely off then back on... I'd take a hard look at the headlamp switch. You can see the breaker in the picture below.

 

Ok - so what's the procedure after taking a hard look?
Is there a fix for the breaker causing the flickering?
One of the 4 new switches I've bought and I installed was from Willcox (although they all look like they came from the same source, same tools, etc.).
They all exhibit the high-beam flickering after ~10 seconds.
And they all are poor for retaining the end of the **** shaft.

 

That is exactly what is happening - all four off and all four on - switch it is then. There is quite a bit of speculation that the newer switches are not of the highest quality and this problem appears even with the new switches. I could replace all headlights with LEDs to lower the amp draw and prevent this issue? Replace the switch and hope for the best? Or re-wire and introduce a relay in the mix that would funnel the amp draw instead of leaving it for the switch.....

 

Use relays and as a bonus you'll probably see an increase in light out put as you'll have less volt drop to the headlights.
Graham

 

Not the alternator - took it for another drive tonight and when I brought her back, I turned the high beam - once they started flickering, I turned the motor off and the flicker continued for a few seconds. It definitely sounds like the breaker in the headlight switch.

 

SO-

You need to check/clean the grounds first- then the connectors on harness to the bulbs and the bulbs connectors. Not positive on a 79- but I think the harness/headlight ground is on the front surround header bar.
Thank "Alan71" for this pic





If it's a new switch- all bets are off....
You can try replacing- but that's not a cakewalk- and especially since the definition of insanity is doing the same thing over and over again and expecting different results-what Bergerboy has done- might not be good for your mental health!!!

You can replace the bulbs with LEDs- they do pull less current.

Or you can add relays- which will take the current draw of both the light switch AND the dimmer switch.

Here's a diagram- there's kits out there to do this-

 

I almost pulled the trigger on a new switch but after further research I think the right thing to do is to splice in relays. There is a pretty nice youtube video on this exact mod on a C3 Corvette

 

Rather than cut up the OEM plug- get one of these for around $5- it'll plug right in the factory harness. "H4 Headlight Connector"

I'd also get a couple of good relays-like a real Bosch but now owned by Tyco ...as we all know how well the Chinese ones might work!!!



These are just 'better'- and I've been using them for over 30 years w/o failures!!

 

It's your thermal protection inside the switch as others have pointed out. My bet is higher wattage halogen bulbs have been installed and they now draw more current than the thermal protection switch can handle with all 4 lamps burning. The original bulbs were not halogens.

You can check your grounds but I'd install relays. I did and now instead of getting a little over 12 volts to the lamps I now get 14.6 volts (full alternator output) to my lamps. Just those couple of volts increased the light output tremendously. I suggest not using the original wiring harness to the lamps. Upgrade the a larger gauge wire and gets some good ceramic plugs. This way in the future if you want to go HID or some other high current lamp you'll be all set.

I went through two switches. On one the part of the switch that the vacuum valve lever went into was broken and the other had the same blinking problem you're having. The only thing wrong with my original switch was the interior lights rheostat. It was broken so I couldn't turn on the interior lights by turning the ****. After going through two "new" switches I rebuilt my original switch using the ceramic/rheostat from one of the new ones and all the original parts.
That is when I decided to install relays.

My circuit is a little bit different than Richard454. I wanted a little more safety built in so I isolated my low beams from my high beams. Overkill? Probably but I feel better about it. I've also replaced the 20amp fuses with self resetting circuit breakers.





Of course this all assumes you are not into originality.

 

I was in the same boat as Theandies.
I originally had a broken rheostat coil which was causing the Gauge Lamp fuse to blow whenever I spun the **** to max gauge brightness.
Four switches later (all Chinese $20-$30 jobs), I then discovered the breaker issue was now creating the flickering on high-beams only.
Since the original switch's breaker was not giving me this flickering problem, I tackeled the rebuild last night, taking a donor ceramic rheostat housing from one of the new swtiches, and fitting it up to the original factory switch.
Got both problems knocked now.
(also got me back to the better factory retention back of my **** shaft - woo hoo!)


I did upgrade to halogen bulbs last fall (all 4), but since the original switch's breaker seemed to handle the higher amperage ok, I decided to see if I could get away without the relay upgrade.
BTW - the "breaker" seems to be no more than a thermo-metallic arm with a contact at the end (see Willcox's diagram in above post). Looks to be designed to move the contacts apart if the arm gets heated by increased amps (hence the flickering). I had contemplated seeing if I could simply take that arm and "tweak" it a little tighter to the contact so it stays "made" longer. But thought there might be an increased risk of an actual overload from the brights if I adjusted the breaker to a higher amperage trip point ths way.
Anyway - I think I'm happy I got this checked off the list before the long winter's nap.
Thanks for the help.