Headlight

[TexasJim]

Hey guys, I didn't see an exact match to my problem when I searched. I have a 2001 le 4x4. I've noticed my driver's headlight occasionally goes out but comes back on in few minutes. Its low and high beam at same time. I'm guessing there are no individual relays on this thing? It seems to happen randomly, I mean movement of car doesn't effect it. It happened last night in a drive through. Any ideas on where to start?

[hawairish]

I’d start by swapping the bulbs left <-> right and see if the issue travels. Inspect the wires for any issues. With a multimeter in continuity mode and lights off, you can try probing the low and high signals to see if there’s continuity, suggesting a short somewhere. Then, with test voltage/signal on low and high when on. Just both headlight sockets for consistency. 
 

My guess (and lowest hanging fruit) is the bulb, maybe something odd going on internally…wild guess. 
 

Does your LE have anything special about its headlights? I thought some had optional adjustment or different bulbs/lenses vs. SE models. Not sure. 

[TexasJim]

Nothing special, my problem is it's so irregular. It may go another month before it acts up again. I tried find a bad ground but I couldn't. I do have fog light bulbs out, new one will be here today, but I can't see the link between them. Thanks for help

[Slartibartfast]

Yeah, intermittent issues can be a real PITA to track down.

 

I had a weak connection in the headlight plug cause a similar fault on mine. I just tweaked the contacts in the plug and it came back around. Hasn't acted up since. Wiggle the plug when the lights are on and see if the bulb flickers. The plug on mine wasn't burned, but that's another thing to check for. Loose or corroded connections can make a lot of heat.

[TexasJim]

I'll clean everything I can this weekend, thanks guys.

[hawairish]

My reason for asking about any special features on your LE headlights is because there could also be a control module in place.

 

Long time ago a buddy had an Infiniti J30 where the headlights kept flickering or turning off random; would work fine for a while, then not work.  I spent hours tracing the issue and eventually took a real hard look at a headlight control module under the hood.  Took it all apart and found a couple solder joints on the back of the control board had hairline cracks.  Resoldered it, problem solved.  I know there were some premium headlight options, I'm just not sure what they were aside from leveling options.  I haven't scoured the FSM to see what options there were.

 

In your case, you still may want to just swap bulbs and wait it out to see if the problem travelled.

[TexasJim]

Only option is the auto feature, 

[TexasJim]

What exactly do the two relays do? Is it just for the auto settings? 

[Slartibartfast]

I had a look at the manuals. Not sure if yours is VG or VQ, but the diagram is on EL-37 in either manual, and looks about the same. They sure crammed a lot of crap into that circuit, and amusingly, power to the bulbs still isn't properly relayed. It's just the WD21 wiring, but backwards, with a battery saver module riding it piggyback.

 

The relays are how the battery saver control unit turns the headlights off if you leave them on for too long with the ignition off.

 

Battery positive goes through two fuses to the two headlight relays. These relays are controlled by the headlamp battery saver control unit. That unit controls both relays together (single trigger wire that Ts off to the two relays). When the relays are engaged, they supply + to the common pin on each headlamp. The high/low filaments in the bulbs are grounded individually through the headlight switch.

 

I'm ruling out the module, because it can't turn on one relay but not the other (if that was bad, it would take out both sides at once). If the switch was bad, I'd expect it to drop one filament at a time, like the WD21 headlight switches do. But each fuse and relay does one headlight, so one bad fuse or relay would take out high/low on that one headlight.

 

Just like with the headlight bulbs, I'd check for any obvious heat/corrosion on the components and the fusebox, and maybe give them a wiggle to see if the light flickers. If it all looks good, you could try swapping them side to side to see if the issue follows the relay. If you're lucky enough to catch it while it's acting up, you could tap the relays to see if that brings it back on, or test for 12v+ at the common pin at the bulb to verify that the problem is on the + side.

Edited April 16 by Slartibartfast

[TexasJim]

Thank you very much, got a better understanding now. But first I have to change both CV axles. One started growling at me. Least they are simple to figure out. Wiring is a nightmare.