I had a flickering low beam headlight issue in my 90 22re pickup. I ordered a relay harness kit(in photo) and now I have the same issue well actually now I have no working low beams. I’m blowing the pass side headlight fuse as soon as I turn the headlight switch on.

Not the most skilled with electrical but I know the harness was installed correctly.
My next step is to try and make an extension for the drivers side headlight socket to connect it to the male plug on the harness (it’s currently connected to the pass side socket)
My hopes are that there is a short somewhere In the stock pass side light socket and that by using the driver side socket, I will bypass that short.

Does anyone with better knowledge of this stock wiring for the headlamps know if this would be a good next step to try?
Or anyone with experience with this problem be able to help talk me through solving the issue?

My truck is about to have a first start after a 10 month long rebuild and really gotta get this figured out soon.
Thanks for taking the time to read this and hope to hear some feedback.

 

Very likely that burnishing the dimmer contacts in the steering column will fix your issue.

Sorry, no time now to search the forum for pertinent threads. Someone else will chime in.

 

It's not good troubleshooting or a good idea to just hack into your harness and modify it in the HOPES of fixing your problem.
with a meter and a wiring diagram you can figure this out, but as millball said, the dimmer switch contacts are a common problem with these trucks.
Start with the basics, do you have the correct amperage fuse?
Do you have any auxiliary lights tied into your headlights or any other non-factory "alterations" to your headlight wiring?
If you unplug the passenger headlight does the fuse still blow when you turn the lights on?

 

this relay harness simply plugs into the existing female socket for the pass side headlight. I’m just saying my thought was to get another male and female h4 socket and make an extension so that I can plug the drivers side stock socket into this relay harness.

Just figured there was a short somewhere in the passenger side socket or wiring since that fuse keeps blowing.

I will take the switch apart and try the recceomemed above comment. I did read about cleaning up the contacts. Just seems weird it’s only tripping the passenger side fuse.
I will try to unplug that side and see if it still blows the fuse.
i do have a multimeter but Unsure of how to use it to check for issues.
Thank you

 

If it is indeed a "relay harness" it shouldn't "simply" plug into the passenger headlight socket. It should also connect to your battery with a fused lead and also to a ground. It should only be using your existing headlight circuit to control the relay which then supplies power to the headlights.
So if it is blowing the fuse for the passenger headlight it would do the same for the driver's side.
If it isn't wired right you may have just doubled the load on the fuse by running both headlights on one original socket.
Do your stock headlights work without blowing the fuse (no aftermarket harness)?

 

I was having this same issue before wiring in the relay harness. And yes, this harness does have 2 grounds, a fused power wire to the battery, and 2 relays to the body. Was just saying by trying to use the drivers side headlight socket, I would t be hacking up anything like you stated in your first comment.

and from your last comment I see that by trying to just use the other headlight socket I will most likely still have this problem.
From what I’ve gathered from all of these replies, I will try to disassemble the headlight switch first.
I just thought that maybe something was up with that passenger side socket or wiring since it’s the passenger side fuse that keeps blowing.

I’m not great with electrical. If you have any thing else to reccomend I try.. it would be appreciated. Thanks

 

Also, I am just running both headlights off of the one socket. That’s how the harness is set up. The drivers side stock socket is unused.

 

That's because the aftermarket harness is using your stock headlight circuit to energize the relays (low current draw) and the relays are powering the headlights when energized (higher current draw) directly from the battery.
somewhere in your circuit you have a short or extra loads that are allowing more current to flow through the fuse than it is rated for, so it blows. since it does the same thing with the aftermarket harness (which should be drawing less current than your stock setup) it sounds like you have a dead short when the lights are turned on.
I can see your picture now, simple setup.
check to see if the fuse still blows with no lights connected, put a meter on the output of the switch set on ohms and check to see if it shows a dead short (still with the lights unplugged).
If you have a wiring diagram it would help.

 

Thank you, I will give a shout back after work tonight after trying this. I appreciate you helpin.

 

So I took the switch inside on the steering column apart, cleaned up the contact points.. and then put it back together, disconnected the plug from the new relay harness from the stock passenger side h4 plug and then turned the headlight on. The fuse instantly blew.
what does this tell me? I’m still lost on electrical stuff.

 

This means that there is a dead short somewhere between the switch and the headlight.
you need a wiring diagram and a meter, put the meter on ohms and connect one lead to a good ground and the other to the output from the switch.
you will likely see a very low number on your meter, but with the headlights unplugged this should read OL for open loop, as in no connection to ground.
from there you will be disconnecting connectors (found on your wiring diagram) to see when the connection to ground goes away. This is the only way to troubleshoot this without sacrificing fuse after fuse after fuse.
You need to see if a wire is pinched somewhere and touching ground.
If I have time I'll try to find a wiring diagram to use as an example, but it may not match your truck.
Or you could put a bigger fuse in and follow the burnt wires to the exact spot of the short, (I'm joking, please don't do this!)

 

so just put a bigger fuse and look for smoke or fire? 😂
thanks! I’ll try to wrap my head around how to use the multi meter and do this. Just can’t wrap my head around it yet. Sure it’s simple, just don’t understand the concepts of electrical yet.
I’ll post back with what I find.

 

Hold the phone...



This may not match your truck, but it reminds me that Toyota does some things backwards from what would be conventional. Having the whole diagram would be helpful, but this is all I could find.
normally you would expect one pin on the headlight connector to go to ground and the other two would be powered by the switch, one for low beam and one for hi.
in this case the power goes to the center pin and the headlight switch grounds one of the other two to turn on the light.
if your fuse blows even when the connector is unplugged from the light you have a short at the headlight plug between the red/black incoming power and the red/yellow low beam wire. EDIT: (might be the red/green wire, looks like the high beam indicator is controlled by the low beam circuit.)
To confirm this you can turn off the headlight switch, unplug both headlights, set your meter on OHMs (the horseshoe shaped symbol) and check for a connection between red/black and red/yellow. EDIT: (Check red/green also)
when working correctly there should be no "continuity" or connection and your meter should read open loop (OL).

 

Man I just can’t seem to wrap my head around this wiring and using the meter correctly for some reason.
Heres some more info I may not have included.
Before I installed this headlight harness upgrade, the issue I was having was one of my low beams would flicker on and off.. then it went to both of my low beams flickered on and off.
So while doing an engine rebuild, I wired this harness upgrade in for the headlights. Now I have no headlights working, neither low or high and no high beam indicator on dash coming on. And the passenger side headlight fuse blows instantly when I turn the combo switch on.
Ive untapped the harness from the passenger side stock headlight plug all the way to the fuse box and see no abrasions or any burnt wires.

So youre saying it might be a short at the stock plug? I will try to do as you say by testing it. But I don’t think my multi meter reads “OL”.
i set it to ohms and got some readings but wasn’t real confident on what I was doing or able to make sense of any of it.

Guess ill have to take a quick lesson on how to find shorts for dummies.

If you could spell this out for a 3rd grader to figure out, I may have a chance 😂

I can rebuild a whole engine but am stumped on this.

 

Just a couple of pictures I found on the net. This only works when the meter is set to read OHMs resistance or continuity, not volts or amps.


Dead short (also may be referred to as continuity meaning you have a continuous connection, like testing from one end of a wire to the other) this means there is very little resistance, in this case only the natural resistance of the test leads.



Open loop, across a switch means the switch is open, from one end of a wire to another means the wire is broken, no connection

 

ahhh. Thanks so much for that. Thought I had it set to ohms but apprantly didn’t.
I will now try to figure out how to test each wire and trace the problem area down.
Still feel clueless while doing this but trying to understand the concept more.
Will report back with what I find soon.

 

There are 4 wires coming from the stock plug.
The left prong is red/yellow, the right prong has a red/black and also an orange/purple (grounded to body), and the top prong is red/green.

theres no connection between any of them except for between the red/green and the right prong with the 2 wires(red/black & orange/purple).

Does this tell me anything? Or help me decide where to trace wires.. what is the next step?

 

If the wire colors of Akwheeler's wiring diagram (quoted below) are correct, then you have the positive voltage feed for the passenger side headlight and a body ground connected to the same terminal, which is a direct short and would definitely blow the passenger side headlight fuse, even with no headlight bulbs connected.

Did you add any of these wires?

 

I know the issue I’m having is separate from this headlight harness upgrade I bought as it was disconnected and I’m still blowing the fuse.

But here is the link for the harness ness and I want to be sure I’m not going to have another issue with it. I see most who buy this harness also upgrade to led headlights which if I’m not wrong, have a different polarity than the stock headlights?
Just want to make sure this harness is compatible with my stockers.

Habe any idea?

https://www.amazon.com/gp/aw/d/B07B9QQMMH?psc=1&ref=ppx_pop_mob_b_asin_image

You don’t know how much I appreciate the help.. I’d be stuck in the water without it.
Here’s my number if you feel like shooting me a call. 813-760-2sixsix2

 

Reading wiring diagrams is tough. Not sure how to read this correctly.

Heres some pics of the stock passenger h/l plug and where the orange/purple is grounded too. I didn’t add any of these wires. But I do feel like the orange/purple wire was not connected at one point and I reccomected it. It’s been a while and my memory is shot. I may have just re-did the connection the inner fender.