Headlight issues

[mikem891]

I have an 89 chevy suburban with dual headlights and i noticed the other day out in the woods that when my highbeams were on they flashed on and off every few seconds. now both the low and high beams turn on and off every few seconds. all bulbs are new also

 

[rebelgregory]

Are they doing this rhythmically or randomly?

 

[mikem891]

It seems to be random aside from today, it hadn't done it for about a week or so until tonight were the low beams kept turning off then coming back on about every five seconds. I tried switching to the high beams and they were doing the same as well.
Even when manually turning them of with the headlight switch then back on they still were flashing.

 

[rebelgregory]

I was hoping you'd say randomly, in which case, it's a short or open circuit somewhere. Probably a bare waire touching something or a loose connection.

I've got nothing for a steady on/off pattern.

Maybe someone else has a better idea, but if it was me, I'd take a multimeter or a test light and start probing the wires until I saw a constant power supply when the switch is on (start at headlights and work back to fuse box (don't ignore the switch itself). If you can do this while they are twitching, find a spot in the circuit where the power is constant and a spot in the circuit where it is on/off with the headlights and the problem is between those two points in the circuit. Just narrow it down from there.

 

[mikem891]

Thanks guess that means its time to start tracing wires

 

[89k5350]

ok first take the connector plugs off the back of all the headlights and put them back on. please do that ,those connectors can do wonders when loose if that doesent do anything fiddle with the wires that go into the connectors that happen to me but more rapid and after fddling the connectors it was fixed

 

[Fordum]

One thought. Did you change the power of the lights when you replaced the bulbs. Headlight circuits must have self resetting circuit breakers instead of fuses by law. A partial short will cause them to stay on for a while until the breaker heats up and then go off until it cools.

Its not uncommon for some brighter aftermarket bulbs to draw more current than a breaker can handle.
Also, breakers can just get old.
Plus, since they work off heat, if there is a bad connection at the breaker, it will heat up under a normal load and flash.

When a breaker switches a load off and on, it burns the contacts slightly. Its possible that when it started flashing on high beams, it caused the contacts to burn enough so that they are not making as good contact as they did, which makes them now flash on low beams.

 

[mikem891]

I didn't even think of that. They are brighter bulbs I switch to the xtravison bulbs instead of the standard sealed beam.

 

[diesel4me]

I am pretty sure the headlamp switch itself has a curcuit breaker in it--that can become weak with age,or not be up to the task of handling higher wattage lamps,and it will trip,reset,trip,repeatedly..................................................................................................I used to sell lots of headlamp switches for Crown Vic police cars,they would not last long with the additional lamps they added to the cruisers..the mechanics at the town DPW ended up using external relays to power the extra lamps ,that were turned on by the headlamp switch,instead of letting the switch take all the load...

 

[bigred88]

I had a similar issue in my car. I had wired in new pigtails, and stupidly connected black to black, white to white, and green to green without consulting a wiring diagram. Turns out the white on the aftermarket pigtails should have went to green, and vice-versa. So if you've done that recently, double check the wiring- headlights do weird things when you wire the low beam to the high and the high to the low.

Also, in my search for what was wrong, I was told that failed headlight switches and high beam switches can cause similar problems, especially if the failure allows current from the high circuit to get to the low, or the other way around. You might also want to inspect the wires near the pigtail and where they're close together- if any of them have worn down over the years and left wire exposed there might be current crossing between the two circuits.

 

[Fordum]

I didn't even think of that. They are brighter bulbs I switch to the xtravison bulbs instead of the standard sealed beam.

Good chance that is your problem.
There are two things that can go wrong when you increase bulb power.
One is increased current causing the breaker to trip, and in extreme cases the brighter bulbs can run hot enough to melt the headlight lens.

Fords mostly have the circuit breaker in the switch. Not sure with GM. I see more and more circuit breakers plugged into the fuse panels these days.

You can either try a new breaker to see if it can handle the new bulbs, put the original type bulbs back in, or fix the whole problem with a relay setup.

Obviously the relay setup is best. It will let you run whatever size and brightness of bulb you want, and take all the load off the circuit breaker.

 

[Burbdood 74]

Check your grounds too. I had the same issue and it turned out to be a loose ground wire.

 

[mikem891]

Thanks for the ideas and help, turns out there is a breaker in the headlight switch so I put a new one in and it seems to have fixed the problem.