View Full Version : Headlight Malfunction?

4runner luv
03-08-2010, 09:32 PM
Ok, this is probably very unexciting compared to most of the posts here, but; My low-beam (and only low-beam) head-lights stopped working tonight. High-beams work, but not low. Fuses are all good, interior lights work, side-marker (corner) lights work, tail-lights work... any thoughts? oh, 1996 4runner. I intend to research for myself, but thought I would get this up, because y'all are pretty awesome here, and between the regulars on the forum, seem to know just about all there is to know on the subject of the greatest manufacturer of trucks ever (hoping flattery will get me everywhere).


03-08-2010, 09:45 PM
Did you check the bulbs themselves? Not sure of the likelihood of both going at the same time but you never know...If nothing else just unseating them and reseating them might do the trick. On my '97 FZJ80 the PS light would go out...If I unseated the bulb and put it back in the bulb would magically start working again :confused:

03-08-2010, 09:55 PM
Assuming you checked that the bulbs were good...

I dunno if the 3rd gen 4Runner is the same, but on my generation truck the headlight switch in the steering column is routinely a PITA. Remove the screws that hold the plastic trim on around the steering column, pull the harness off the switch and remove it. Clean the dirt and dog hair and crud out of it with contact cleaner.

4runner luv
03-08-2010, 10:31 PM
I considered that, but I just replaced one of them about 2 months ago. Still is possible though. My research in the last 20 minutes suggests it is most likely the switch within the steering column; Good ol' Haynes manual shows a separate continuity test with ohmmeter for low-beam and high-beam. So, the switch can go out, and allow either high- or low-beam to go out independent of the other... yeah? Only one relay; though, internally maybe it is segregated (racist relay?). To replace the switch, have to remove steering wheel and steering column covers to get to it. Spose there is always Jim's or the Yota Yard. Ya know... they really should have links to Rising Sun... I'm fairly sure, we have brought them an appreciable amount of business... I know I have recommended them b4... FREE PARTS?

03-08-2010, 11:45 PM
not sure what truck you have but alot of car;s have seperat relays for high and low. your low beam relay might be bad. check and switch with the high to see if the high dosent work or swithc with the horn or similer relay so see if thats it.. its either the low relay or the bulbs.. highly doubt its the switch

4runner luv
03-09-2010, 02:19 AM
Only one relay... combo for high- and low-beams. I pulled it, shook it, blowed in it, put 'er back in... no change. I'll give "the zone" a call tomorrow and see what a new one costs... maybe try replacing a headlight too... wouldn't hurt to have spares I guess, if they are not the problem. Hard on the unemployed pocket book (that's a wallet for all you unsophisticated fellars).

Uncle Ben
03-09-2010, 05:10 AM
Only one relay... combo for high- and low-beams. I pulled it, shook it, blowed in it, put 'er back in... no change. I'll give "the zone" a call tomorrow and see what a new one costs... maybe try replacing a headlight too... wouldn't hurt to have spares I guess, if they are not the problem. Hard on the unemployed pocket book (that's a wallet for all you unsophisticated fellars).

If your highs work and your lows do not replacing the single relay will not cure the problem. Before replacing the headlamps at least pull the plug of the rear of one and check the terminal for current. I would put a wager on the dimmer switch. Unless something was done recently in the cab or in the engine bay where the harness was disrupted it's unlikely in the wiring. Before you just start throwing money at it until the problem goes away I would start checking some continuity on some plugs starting with the headlamp control. Attached is a scan of the headlamp circuit on a 98 Runner. Yours should be the same....

03-09-2010, 06:35 AM
UB's right (again). It stinks, but the only way to figure this out is a trace-back or elimination procedure. I absolutely hate electrical for this reason. I have even replaced partial looms once a break is isolated rather than stripping and pulling an individual wire.

03-09-2010, 07:51 AM
In my truck the contacts for the low beams had corroded to the point that they stopped working. I had to clean and re-solder the contacts. Most people just toss it and get one from a junkyard but cleaning them is not terribly difficult.

The circuit that Kevin posted looks very similar to the one in my truck, which means it probably suffers from the same weaknesses. The main one is that the steering column switch switches the grounds to the headlights, so all the current from the headlights flows through the combination switch.

After getting them to work again your next move should be to put in some sort of headlight harness that only uses the combination switch to energize relays that do the switching. I got mine from Roger Brown but I imagine there are other options, too.

4runner luv
03-09-2010, 08:28 AM
Geez, it's been so long since I've used my multimeter, I don't think I remember how... guess I better relearn... at least if I wanna drive at night. Thanks guys, you have convinced me to try and trace it. Haynes did say on the combo switch, that I can test for current between a couple of numbered pins, so I guess I can start at the headlights then work my way back to the switch. Y'all prolly want pictures now huh? Cuz voltmeters are so cool lookin!

Air Randy
03-09-2010, 08:45 AM
I had the same problem on my 85 mini truck. I cleaned the switch Dave refers to, tested the H/L relay all to no avail. I started tracing the wiring out, took all damn day with half the truck disassembled but I finally found it. There is a wiring loom that goes from the passenger compartment to the engine bay that is routed through the inside top of the passenger side front fender. One of the supports came loose and the loom sagged down enough to touch the top of the tire when the suspension was compressed. It wore through the loom and broke 1 wire, which went to the H/L relay.

03-10-2010, 12:04 AM
if your still haveing a problem call me.. i have a complete master power probe diagnostics set with short/open detector.. and i love electrical. so i could figure out your electrical problem in a matter of minutes im sure.. if not i could at liest conferm that your light circut is probly good or bad and that your swith probly bad.. all with just the power probe.. just let me know.. 720-383-ten 13. odds are i wont answer the phone so leave a message. best yet just text message me and say " hay timztoy it's"

03-10-2010, 08:12 AM
Randy: There is a TSB pointing to your loom wearing through on the passenger fender if I recall.

Great place to start.

Air Randy
03-10-2010, 08:27 AM
Oh sure, now you tell me, after I already figured it out the hard way :D

4runner luv
03-10-2010, 01:53 PM
I might take you up on that Tim; I'm headed over to my sister's (she has a garage) in a bit to see if I can track it down. If not, I will definitely give you a call. Thanks.

4runner luv
03-11-2010, 12:10 AM
ok, so one bulb (the one I installed new about 2 months ago) had a burnt out low-beam element. Other bulb looked fine, so why wasn't it illuminating? Checked voltage on the plugs and it was as it should be... a little over 12 volts constantly on the relay wire, 12 volts on the high beam node when the highs were switched on, and 12 volts across the low beam node when the lows were switched on. WTF? So after getting frustrated, the one good bulb got rattled around and the 4runner gods said let there be light.

Long story short... within a span of 24 hours, one bulb had the low-beam element blow out, while the other had the low-beam element become intermittent. Checked the intermittent bulb on both sides to be sure it wasn't the connection, and it was definitely the bulb. So, it's both bulbs I'll be a replacin'. That'll be about 40 bones. Prolly more expensive than the switch from a junkyard, or a new relay. Ah well, easy fix at least.

Thanks for all the advice guys.