This is probably a question that has been asked a million times, ive been reading some of the older threads and troubleshooting for a while. Here goes....my low beams work great, my fog lamps work great, when I engage the High beams they illuminate and work fine for about 2.5 minutes or so, then both the high and low beams flicker on and off over and over together at random intervals. When i select back to low beam the problem goes away. This is happens whether the engine is running or not. An audible "Click" can be heard at the firewall on the drivers side of the engine compartment as the lights flicker on and off. This noise is also heard when I manually engage the hi/low beams on the wiper lever. The headlamp bulbs were replaced a couple of years ago. Any help would be appreciated. Headlamps drawing too much? weak relay somewhere? Hi/low beam switch weak?

 

Have you tried tracking the clicking? What component is causing it? Could it be arcing inside a wire?
There are no relays in the headlight wiring path. Only the fog lights use a relay. If you turn off your fog lights, does the clicking still happen with your high beams flickering? (the fog light relay is controlled by the high beams so that the fog lights turn off when the high beams come on).

Does the flickering speed change with the engine on and off?

Your best bet is to find the source of the sound. That would tell you a lot.

Let us know what you find, I am curious.
Lou

 

The clicking sound doesn't really sound like arcing. It sounds more like a relay click. I agree that there is no relay in the circuit. It clicks behind the brake booster. I think it's at the plug going through the firewall. Maybe a bad connection at that plug? Too much resistance when the highbeams are on? I'll keep digging.

 

Clicking sound was just the fog lamp relay. It's working great. Headlights are still not. When I unplug any one of the four headlamps the problem goes away and the rest of the lights work great. Could it be the headlamps themselves?

 

The fog lights relay clicking is a good clue, thanks.
That means that the power to the high beams is being interrupted.
And if you unplug one of the headlights, the flickering stops, that's another great clue.
It definitely points to a problem in power supply.
Definitely good troubleshooting.

I would recommend tracing the power backward through the high/low beam switch, light switch, the C100 on the firewall and ultimately the fusible links on the positive starter post. I would use a test light, not a voltmeter, because you can see the light flicker better.

Let us know what you find.
Lou

 

Tested the wires at the headlamps (obvious results) and at the fog lamp relay, and at the hi/low beam switch mounted under the dash on the column. Green wire (power to the high beams) flickers when the high beams are engaged. That kinda goes without saying at this point. I did find that the yellow (power in) wire going to the hi/low beam switch is very hot to the touch when it is plugged into the switch. And I cannot currently duplicate the flickering headlamps after unplugging and re-plugging the connector into the switch. Without being able to get the failure to repeat I can only guess that the hi/low switch is the culprit? I have the connector installed and I have the power in wire back-pinned to test for the flicker. But I cannot duplicate the problem. And the wire is getting hot enough that I'm not comfortable with driving it in this condition. I'm thinking its hi/low switch replacement time unless there are any other suggestions?

 

Hot switch means high voltage drop across it (even intermittent, which would explain the flickering) which indicates a bad contact meaning likely a bad switch. You might have just found the culprit.
You cannot lose by replacing the switch if it is getting hot. Don't forget to adjust it right after you replace it. Quick procedure here: http://www.austinthirdgen.org/index.php?pid=16

Let us know how it goes.
Lou

 

I had the same problem, but without the clicks. Turned out to be a bad connector on my driverside high light. I just spliced in a junkyard pull connector and problem solved.

 

Hey guys did you ever figure out the cause of this? I have an identical issue on my 87 iroc.

 

 

The lights are stock and the switch is brand new acdelco. Maybe the switch is faulty.