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Old 12-30-2019, 02:49 PM
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04 TJ LOW/HIGH Beam Failure *EPIC*

Hi guys! This is my first post on the forum so hopefully I don't break any rules. This is a long post, as I have done quite a lot to try and fix it..

A few years ago my best friend died and I inherited his '04 Columbia Edition TJ. When it was parked it was not in the best condition, and it sat for an additional two years before I was given the ownership of it. I could go on and on about my journey of repairing it but i'll cut to the chase!

**This is a Canadian jeep with DRLs. Both grounds above headlights are spotless, as well as the two main grounds that bolt into the cowl area. **

So the low beams would cut in and out. I replaced the multi-function switch and then the lows+highs would not come on at all, but now the fogs worked again! I noticed the C1 Connector is not in the best shape, burnt, so replace it as well. Still no lows or highs.

I then verify if headlight bulbs still function (not burnt out) by delivering 12v from battery and a ground and they come on.

I then measure voltage at headlight sockets. 12.1v at either the high or low pin depending on your selection at the MFS; however, plugging in the the passenger or driver side socket brings the other socket to 0v. This leads me to believe my new switch is not faulty, but to confirm my hunch I disconnect it and straight up jumper the pins 16, 18, and 19. Nothing happens. Pins 18 and 19 both have 12v.

I jump the grounds coming from headlight sockets directly to .neg terminal and attempt to use switch to turn on lights, nothing happens.

I jump 12v from battery to headlights and attempt to use factory grounds above headlight terminals, nothing happens.

I buy a relay kit for $50 and plug it all in, low beam and high beams worked for 20 seconds properly before failing. Frick. With relay kit installed the high beams now only work if you flash them with the MFS selector in the off position, as if you were driving during the day. Low beams do nothing, and you cannot flash/use highs when the MFS selector is at low beam.

I supply 12v from battery to low beam of relay kit and ground it to .neg terminal of battery and verify the kit works, and that both headlights work together when I manipulate the passenger side socket. All good. Jump 12v from battery to high beam pin of relay kit and ground to .neg of battery, all good.

Fooling around, I measure continuity between the low beam wire at headlight socket and ground at headlight socket, and find it shows 250ohms of resistance or something like that, which confuses me?? Does this mean these two wires are shorted to eachother somewhere? The ground at headlight socket shows 0.2v when I select low beams. If it was shorted to eachother would it not show 0ohms of resistance and 12v of power??? AHHHHH

So hear I am stumped, I am not really sure how to proceed. Right now I can either start tearing apart the entire wiring harness which is extremely daunting to me, or I can just bypass the entire system with a rocker switch, which is also daunting to me, although slightly less. I would have to find a wire that is hot when the MFS is in the low beam selection to power a 3 position rocker switch that goes to the relay kit. Not sure how to go about doing this though...

Either way, sorry for the novel. These headlights have made me crazy.

TLDR: Headlights don't work, replaced MFS and C1 connector, no dice. Grounds good. 12v at headlight socket until you plug either driver or passenger into the bulb, then 0v at both. 250ohms of resistance between low beam pin and ground at headlight socket connector.

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Old 12-30-2019, 04:58 PM   #2
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What happens if you unplug the DRL module?

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Old 12-30-2019, 05:19 PM   #3
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Epic, good luck
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Old 12-30-2019, 06:35 PM   #4
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Welcome to the Forum AlpineBurnmouf,

Do TJs have a headlight fuse?

I can't authoritatively comment on TJs, but YJ's have a bi-metal strip in the headlight switch that acts as a circuit breaker. It seems to weaken over time.
If The TJ headlight switch isn't too expensive, that might be another thing to consider.

Do you have aftermarket headlight bulbs? Even though the headlight bulbs light when battery ground and battery power are used, perhaps there's a short within the bulbs or in the headlight socket itself.

Let us know what you find.

Good Luck, L.M.
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Old 12-30-2019, 07:23 PM
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Originally Posted by RUBI 4 MY MRS View Post
What happens if you unplug the DRL module?
I will give that a shot. I certainly not a mechanic or electrician, or even an experienced jeep owner so I'm feeling pretty stumped on this one.
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Old 12-30-2019, 07:28 PM
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Originally Posted by Luckymac View Post
Welcome to the Forum AlpineBurnmouf,

Do TJs have a headlight fuse?

I can't authoritatively comment on TJs, but YJ's have a bi-metal strip in the headlight switch that acts as a circuit breaker. It seems to weaken over time.
If The TJ headlight switch isn't too expensive, that might be another thing to consider.

Do you have aftermarket headlight bulbs? Even though the headlight bulbs light when battery ground and battery power are used, perhaps there's a short within the bulbs or in the headlight socket itself.

Let us know what you find.

Good Luck, L.M.
Thanks for the comment!

As far as I know, my TJ only has a multi function switch which also functions as the headlight switch. It does not have one of those pull/push rods to turn the lights on. Also, the low and high beam wires at the headlight socket show 12.1v with the MFS in the low or high position respectively. No aftermarket bulbs. I have taken apart the headlight sockets and separated the wires so I know there isn't a short in the socket connector.
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Old 01-01-2020, 12:53 PM   #7
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Unplug the DRL module.
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Old 01-03-2020, 03:00 PM
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Unplug the DRL module.
Unplugging the DRL yielded no results, lows and highs still don't work

I will return today with a multi meter and do some more prodding around.
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Old 01-03-2020, 03:23 PM   #9
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I do know that a functioning DRL module sends reduced voltage through the high beams when moving so thought that might be causing this condition.



When you go, take a 12v test light too.

Using a volt meter can cause conflicting & misleading readings. To best test both 12v & ground connections you will get better results using a simple 12v test light. If you happen to be getting very low power (amperage) a meter will read 12v but something like head lights may not even come on dimly. That can cause confusion. “I have 12v & ground at the light but will not illuminate.” If you probe the same circuit with a test light it may not light up or possibly just very dimly.

The same applies to the ground. If you are seeing a low voltage reading from the ground side of a circuit the meter is confusing you. You have resistance or an open ground path but when the meter is hooked into it the meter becomes the ground path & moves the needle or registers a reading as a small current goes through the meter’s circuit. A test light clipped to a good B+ point like at the battery (+) post will only light when the probe is on a good ground. If there is high resistance or it is open, no light, or maybe a dim (compared to the battery ground post) light at best.

Probe both high & low beams wires at each headlight connector with the light clipped to the battery (-) post. Then probe the ground wire in the connectors with the light clipped to the battery (+) post. See what you find.

If bad when probing the high &/or low wires go to the multi function switch & test the same way at the switch outputs to them & if bad, check the 12v feed wire(s) too.

See what you find & report back.
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Old 01-04-2020, 02:55 PM   #10
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Note - '03 thu '06 do not have a separate headlight switch on the lower left dash as the '97 - '02s do. The headlight switch is part of the mulit-function switch which as not only the turn signals, but the headlights and fog lights (in some vehicles).

There is a 40A Cartridge Fuse in the PDC (position 3) for "Exterior Lighting" (at least in that pos on my '03 which is very similar to the '04). If the other exterior lights work, than that fuse is probably good.

The probe that Rubi_4_My_Mrs mentioned is one like this:
https://www.napaonline.com/en/p/BK_7...t+probe+tester

Amazon has them, but they are about the same price as the one from your local NAPA store, and you can pick one up from NAPA before Amazon can deliver one.

I know you said you have clean grounds. Have you disconnected the ground from the body and cleaned both contact areas?

Another long shot, have you tried cleaning the connections on the headlights? The H4 connection design is not the best, but can easily be cleaned. An emory board can be used to clean the flat contacts on the bulb and then one cut narrow to fit the socket can be used to clean those contacts.

If you have another H4 headlight that you know works consistently, try swapping it into one side of the Jeep and see if it still works consistently. If your TJ still has the Wagner sealed beam headlights they are now 15 years old. I replaced mine when they were 12 years old, not because of a bad connection, just poor lighting. (My TJ now has Quadratec GenII LEDs).
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Old 01-04-2020, 09:01 PM
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Originally Posted by rgreen65 View Post
Note - '03 thu '06 do not have a separate headlight switch on the lower left dash as the '97 - '02s do. The headlight switch is part of the mulit-function switch which as not only the turn signals, but the headlights and fog lights (in some vehicles).

There is a 40A Cartridge Fuse in the PDC (position 3) for "Exterior Lighting" (at least in that pos on my '03 which is very similar to the '04). If the other exterior lights work, than that fuse is probably good.

The probe that Rubi_4_My_Mrs mentioned is one like this:
https://www.napaonline.com/en/p/BK_7...t+probe+tester

Amazon has them, but they are about the same price as the one from your local NAPA store, and you can pick one up from NAPA before Amazon can deliver one.

I know you said you have clean grounds. Have you disconnected the ground from the body and cleaned both contact areas?

Another long shot, have you tried cleaning the connections on the headlights? The H4 connection design is not the best, but can easily be cleaned. An emory board can be used to clean the flat contacts on the bulb and then one cut narrow to fit the socket can be used to clean those contacts.

If you have another H4 headlight that you know works consistently, try swapping it into one side of the Jeep and see if it still works consistently. If your TJ still has the Wagner sealed beam headlights they are now 15 years old. I replaced mine when they were 12 years old, not because of a bad connection, just poor lighting. (My TJ now has Quadratec GenII LEDs).
Yes I have removed the cowl and taken off the two main grounds under the hood and serviced. Grounds on headlights have been cleaned.

I made some progress today with a friend helping me out. We decided to abandon trying to fix it to make it work oem and instead run new wires.

We depinned pins 16 and 17 in the C1 connector for the MFS and placed new wires in the empty slots which will be connected to a 2 wire bundle that will run from the cockpit to the relay for the headlight harness kit.

This solution will retain the factory MFS switch controlling highs and lows instead of wiring in a on-off-on rocker, and will also use already fused power.

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