Left low beam headlight not working

[BICruiser]

Hello, I have an 89' fj62. Recently the drivers side low beam does not operate. The high beams all come on when switched on, but I cannot figure out the problem. There is an aftermarket wire harness installed. The bulb does not appear to be burned out, and when I switched the bulb from the other side it still had the same problem. There are 12v coming to the headlight. I took the switch off at the steering wheel hoping for bad ground but the contacts were very clean. I assume a bad ground there would cause both low beams not to operate anyway. It's strange because the new harness connects to the connection that plugs into the faulty headlight, and then travels to the other headlights and new fuse/relay box (which is wired directly to the battery). Can anyone offer advice. Thanks!

 

[60Works]

You might try swapping the relays in the aftermarket harness. And check the fuses in the aftermarket fuse box.

 

[BICruiser]

I did swap the relays and was unable to change anything, I believe they are all good...

 

[60Works]

Hmmm. Does the light work if you plug it into the original harness?

 

[BICruiser]

It does but it stays on HI (both elements are lit in the bulb) whether it's switched on "HI" or "Lo" which confused me quite a bit.

 

[60Works]

That sounds like a problem with the stock hi/low relay. They are in the cluster of relays under the dash to the left of the steering column. The new harness may be pulling the trigger signal from the the passenger's side bulb.

Or... Are you using the OEM headlights? Some of the aftermarket bulbs are pinned differently and that may be throwing off your troubleshooting logic. The thread "Four eyes of fire" will have good tech and also has links to the original thread of the aftermarket harness you have.

 

[BICruiser]

Awesome thank you very much. I'm not sure which headlights these are, I assume oem. I will research this.

 

[BICruiser]

@Juggernaught, would a factory relay issue cause only one headlight to fail?

 

[BICruiser]

I replaced the headlight relay and the problem still exists.....

 

[60Works]

Did you solve this mystery? I was out of ideas short of ringing out each wire to find what was cross feeding?

There are 3 relays in the aftermarket harness. So, yes, potentially.

 

[BICruiser]

@Juggernaught still haven't figured this one out, on borrowed time as the inspection is overdue.. To the best of my limited knowledge the problem lies between the factory relay and the plug that goes into the aftermarket harness. not sure what to try next..

 

[3_puppies]

in the first post, you stated you had 12v going to the light. is that at the plug at the back of the headlight?

 

[TrickyT]

That sounds like a problem with the stock hi/low relay. They are in the cluster of relays under the dash to the left of the steering column. The new harness may be pulling the trigger signal from the the passenger's side bulb...

Huh? This is a 1989 FJ62, right? There is no stock hi/low relay in that rig, only the main headlight on/off relay which switches the 12v power. All the switching between hi beam and lo beam is done by the combination switch at the steering wheel. It's a very simple, ground switched circuit.

@Juggernaught still haven't figured this one out, on borrowed time as the inspection is overdue.. To the best of my limited knowledge the problem lies between the factory relay and the plug that goes into the aftermarket harness. not sure what to try next..

I don't know what aftermarket harness you have, so don't know how it's wired. If you reconnect all the original wiring to the lamps, does it still behave the same way? In the original factory wiring the DS and PS are wired in parallel, so the two sides have to behave the same. You could at least put in back this way temporarily and get your inspection done, then figure out the problem when you've got more time.

 

[60Works]

TrickyT is correct. The FJ-62 only has one relay allowing power to the head light system.

Sorry about that. I was thinking from memory about how slcfj62 builds his harnesses and in his thread he mentioned setting up his diagrams based on the stock system. Here's his thread:

https://forum.ih8mud.com/threads/headlight-wire-harness-fj60-and-fj62.354712/

Does your aftermarket harness look like his?

If it does, this brings us back to either relay 1 or 2 (whichever feeds the left side), which provide power to the left and right headlight's low beams separately. There is a fuse for each one too. Check the fuses for all the relays and swap relays 1 and 2. The failing low beam will be either the fuse or it will follow the bad relay.

 

[BICruiser]

@3_puppies yes that is correct, 12v to the plug at the back of the headlight. When I plug in the old harness the bulb is stuck on "hi" meaning both elements are lit, no matter which position the switch is in. When I opened up the switch in the steering column, the contacts looked great so I figured that was not the problem.

 

[BICruiser]

Yes @Juggernaught it must be the Ultimate harness built by @slcfj62 , looks exactly like that.

I have switched the relays and checked all fuses, nothing changes..

 

[60Works]

What happens if you unplug the other 3 lamps, leaving only the malfunctioning bulb plugged into the stock harness?

Your symptoms don't make sense. This is not a complicated system. Please tell us what changed in the system. Any new bulbs? A disconnected plug? Installed a radio?

Which pins are you getting 12V at? Which have ground? Are the connectors solid? Is the bulb a stock Halogen or something with a removable element? Does it have 2 or 3 blades on the back? Is there a brand name on it?

 

[BICruiser]

i never did anything to the truck. The low beam didn't work one day, later it would work normally. Now it doesn't work at all. This is all without me touching anything. This truck is new to us and has been one thing after another, one day you get in and no radio, next day a/c fan doesn't work, etc.. Get the picture? The bulbs have 3 blades on the back, GE 12V 60/55W removable element. If I plug in only the faulty lamp into the old harness, the bulb is stuck on "hi". If I plug all the other lamps into the stock harness, both outer lamps are stuck on "hi" and the inner "high beams" are lit very dimly. (When I assume they should be "off"). I'm getting 12V at the factory plugs on one side of either plug, no matter whether it's switched on "hi" or "lo". I'm not sure how to tests ground.

 

[BICruiser]

Maybe the factory connector at the faulty headlight (where the aftermarket harness connects) is bad?? Obviously this truck has some electrical issues, I doubt living on an island in the middle of the pacific helps this at all.

 

[TrickyT]

The inner high beam glowing dimly is an indication of a bad ground somewhere. In fact, a lot of the intermittent problems you mentioned _could_ be caused by bad grounds. As far as the headlight problem goes, troubleshoot the OEM wiring and get that working correctly, then add in the aftermarket wiring harness. Use the top wiring diagram in post #14 as a guide. Use a good multimeter set on the ohms or "resistance" setting. Remove all of the bulbs and pull the two 15A fuses for the headlights so that you don't damage your meter by inadvertently connecting one of the leads to +12v when trying to measure resistance. Then test the ground connections at each socket. You can see from the wiring diagram that with the steering wheel switch in the high position then (reading left to right in the diagram) that one contact on each bulb socket is tied to ground through the switch. I would hope that resistance to ground would be 1 or 2 ohms or less, but if you've got corrosion, a partially broken wire, etc it could be 5 ohms. Anything more than say 10 and I would dig deeper. When the switch is in the low beam position, then one contact on the outer sockets is tried to ground through the switch. The only slight complication in your measurements is the blue high beam indicator bulb in the dash. When the switch is in the high position, this bulb gets fed 12v through the low beam filament. So don't get misled thinking you've got a bad ground when you are really just measuring the resistance of the filament of the indicator bulb. You should still see low (1-2 ohm) resistance to ground on the other contact of the socket.