Headlights flickering...

[midwest]

First off, I probably know and understand less about wiring than anyone on this board, LOL... I replaced all 4 headlights in my K 20 (it started life as a 77 but has an 86 body on it.). The headlights had been in it for 15 years and a couple were burnt out. I just went with stock replacements from the local Oreileys. The first night driving it the lights started to flicker on an off, all of them. If I hit the high beams to switch to those they come on and it stops flickering for a few minutes. Then they start flickering again and if I switch from high to low or low to high it stops the flickering for a few minutes then the same thing. I had to do this for about a 10 minute drive home...
I didn't make any other changes, so I didn't know if a loose connection somewhere would cause this or somewhere else I should look.

 

[Robert Bare]

Chances are your new bulbs are halogen, and drawing more current.
There is a circuit breaker built into the headlight switch, and chances are it is weak, and soon to fail. New switches are cheap.
BUT, you also could have a ground problem, or bad connections.

 

[midwest]

I might just start with a new switch then and go from there... Thanks

 

[3 Ton]

Switch is a good place to start, $20 at LMC, just got one. Im replacing all the switches.
The headlights have several connections from the light switch tot he bulb.
Bad grounding can cause this also.

 

[AuroraGirl]

whats a volt meter say at the battery, then at the headlight socket with the switch on ? low voltage means more current and these headlight systems are notorious for beeing WAYU too long on WAY too thin wires and also being 40+ years old

Get a relay harness regardless of what the fix is, youll have brighter headlights and youll stop pullinh the headlamp current through other things which causes voltage drop, dim lights, higher current, and wear

 

[Ricko1966]

Chances are your new bulbs are halogen, and drawing more current.
There is a circuit breaker built into the headlight switch, and chances are it is weak, and soon to fail. New switches are cheap.
BUT, you also could have a ground problem, or bad connections.

This^^^ or a short in a headlight wire, which is tripping the breaker.And this is why GM uses a switch with a breaker,instead of fused headlights. With a fuse instead of low beam,flicker,off, highbeam, flicker, off, lowbeam is back,flicker,off. A fused head light circuit,is poof! You have no low beam instantly,poof you have no highbeam instantly. With the circuit breaker,slow blow flicker,you have time to slow down safely.

 

[Robert Bare]

whats a volt meter say at the battery, then at the headlight socket with the switch on ? low voltage means more current and these headlight systems are notorious for beeing WAYU too long on WAY too thin wires and also being 40+ years old

Get a relay harness regardless of what the fix is, youll have brighter headlights and youll stop pullinh the headlamp current through other things which causes voltage drop, dim lights, higher current, and wear

Ya, good points. 70's-80's Dodges were the kings of corrosion growing way up into harness wires, Chevy's undersized. Sometimes just adding driving lights could take out squarebody switches, and on the newer chevys burn up the headlight switches and connectors. I can't remember how many relays I have added to peoples vehicles, right at the headlights. Old yellow lights became almost white, halogens quit flickering, switches quit burning out.

 

[midwest]

I am assuming the newer made switches are designed to handle the extra current drawn by the newer bulbs...

 

[fast 99]

I am assuming the newer made switches are designed to handle the extra current drawn by the newer bulbs...

Not necessarily, changing original design could open up the manufacturer to unwanted liability such as an electrical fire. If higher amp draw is suspected run through a relay.

 

[Ricko1966]

I am assuming the newer made switches are designed to handle the extra current drawn by the newer bulbs...

No,most common would be just what was factory,maybe a little less with today's quality parts.But you couldn't up the amperage on the breaker in the switch unless people were also going to upgrade the wires otherwise wires would melt. As @fast 99 said relays would get more voltage to the headlights with less amperage through the switch. You could add relays and keep the old switch with relays tge switchbwill see almost no load.

 

[midwest]

Thanks, I'll still go ahead and try a new switch, then have one of my electrician buddy's help me with a relay.

 

[Ricko1966]

Thanks, I'll still go ahead and try a new switch, then have one of my electrician buddy's help me with a relay.

4 relays. 1 per headlight and function. Wired properly that way, a problem only results in the loss of 1 headlight not all 4 or even losing just high beams or low beams. Nbd in the driveway,a much bigger deal at 90 on the highway. Protect the circuit with breakers. Relay wiring #30 12 volt from battery. # 87 headlight power. #86 relay ground. #85 from old headlight power lead. For example, you turn on headlight low,the headlight low wire now triggers the relay,not the headlight. The relay closes and power flows from the battery to the headlight.

 

[Ricko1966]

Before you do anything disconnect all headlights at the same time. Take a multi meter and check continuity to ground. Each headlight should have 1 wire with almost zero resistance to ground,all the wires should show open if any of them get a reading other than open,I'd be looking for a short first.

 

[SquareRoot]

90 on the highway.

 

[Ricko1966]

^^^^ sorry I meant 89 he's not LS swapped yet.