Weird electrical issue

[Rut Row]

Vehicle: 2003 TJR w/ manual transmission

Issue: 4WD lamp inop and lockers inop.

Background: I was out wheeling at the Wolf Den Run State Park here in Maryland. I turned the lockers on the check if they were working (I usually do that at least once each outing). Everything was fine. We ran through a long stretch of deep mud (The Wallow) and then at a short steep section, I decided to turn on the rear locker for assistance. Nada. No locker. I don't recall if the 4WD light in the dash was on or not.

The service manual says:

DIAGNOSIS AND TESTING - AXLE LOCK SWITCH
(1) Check the fused B(+) fuse in the Power Distribution Center (PDC). If OK, go to step 2. If not, repair the shorted circuit or component required and replace the fuse.

The fuse is fine.

(2) Check for battery voltage at the fused B(+) fuse in the PDC. If OK, go to step 3. If not, repair the open B(+) circuit to the fuse.

With the fused pulled, voltage on the right side of the fuse holder is 12.8 VDC. On the left, it should be 0.0 VDC. It isn't, it varies from 5 VDC to 10 VDC depending on when I test it. Not good. No idea how to troubleshoot that! Moving on ...

(3) Turn the ignition to the off position. Disconnect and isolate the negative battery cable. Remove the Axle Lock switch. Disconnect the switch harness connector. Check for continuity between the fuse cavity in the PDC and the Fused B(+) circuit in the switch harness connector. If OK got to step 4. If not OK, repair the open Fused B(+) circuit.

At first, the circuit was open. I tried jumping from the battery directly to the pink/white terminal on the locker switch and everything worked (4WD light and locker lights.) So I started looking at cables trying to find the broken wire. Frustrated, I went in for a beer and dinner.

If you look at the diagram above, it shows the courtesy lights on the same wire as the locker switch. They work and there is power to the pink/white wire compass connector. The dome lights work. Everything except the lockers work. So I started digging around more, unwrapped splice 204 looking for breaks or fried wire, etc. Nada. The more I looked the more confused I got. ... went in for more beer and sleep.

Today, I decided to start and retest everything again. Today there is still power on both sides of fuse 26. However, there is now power at the locker switch. ARGHHHH!!! I hate electrical issues. I tried jumping from the battery to the locker switch again and this time it didn't work.

I have a splitting headache ...

Two issues:
1. power on both sides of the fuse holder for fuse 26
2. Lockers don't work, no lights when activated. 4WD light not working.


Any thoughts on how to troubleshoot this?

 

[billyp]

I'm confused why you think one side of the fuse should be at 0V? There should be minimal drop across the fuse (both sides should be around 12.xV.

Unclear to me from the description if you tested the switch itself. Sounds like if you apply 12V to the switch output wire, the locker works. Is there voltage coming into that switch?

 

[macleanflood]

Loose or disconnected dash ground? Look under the speaker covers... especially passenger side.

I agree with @billyp and check the continuity of the switches.

-Mac

 

[JEEPCJTJ]

You "ran through a long stretch of deep mud (The Wallow) " and after that the locker stopped working.

Maybe that had nothing to do with the problem but the first place I'd be looking is UNDERNEATH the Jeep, primarily at the compressors and the wiring going to them (if it is even still there).

 

[Rut Row]

I'm confused why you think one side of the fuse should be at 0V? There should be minimal drop across the fuse (both sides should be around 12.xV.

Unclear to me from the description if you tested the switch itself. Sounds like if you apply 12V to the switch output wire, the locker works. Is there voltage coming into that switch?

I should have said with the fuse pulled.

I ran a jumper from the battery to the the switch bypassing the pink/white wire.

 

[Rut Row]

You "ran through a long stretch of deep mud (The Wallow) " and after that the locker stopped working.

Maybe that had nothing to do with the problem but the first place I'd be looking is UNDERNEATH the Jeep, primarily at the compressors and the wiring going to them (if it is even still there).

if that was true, then the lights on the switch and dash would work. They don't.

 

[Rut Row]

Loose or disconnected dash ground? Look under the speaker covers... especially passenger side.

I agree with @billyp and check the continuity of the switches.

-Mac

that is a good suggestion. I'll check the wiring diagram and figure out which ground is used and check that.

 

[LONGJP2]

That power is only for the lights in the switch.
The locker switches send 0v or a ground signal to activate the lockers.

 

[Rut Row]

That power is only for the lights in the switch.
The locker switches send 0v or a ground signal to activate the lockers.

hmmm ... the diagram I posted isn't clear in that regard. It shows going to the switch. However the drawing below though implies all power comes through the pink/white wire.

 

[LONGJP2]

If you're using the factory switches; you need to have the 4wd (low) light on.
Then you need to check if the locker light flashes when activated.
Then listen for air pump.

 

[LONGJP2]

hmmm ... the diagram I posted isn't clear in that regard. It shows going to the switch. However the drawing below though implies all power comes through the pink/white wire.

View attachment 448725

8W-31-15 in the FSM

 

[Rut Row]

If you're using the factory switches; you need to have the 4wd (low) light on.
Then you need to check if the locker light flashes when activated.
Then listen for air pump.

yup. I agree.

 

[LONGJP2]

yup. I agree.

What part of that isn't happening?

 

[LONGJP2]

if that was true, then the lights on the switch and dash would work. They don't.

You may have other problems.
I don't think the locker switches even need power to work.
My override mod switches don't.

 

[LONGJP2]

Two issues:
1. power on both sides of the fuse holder for fuse 26
2. Lockers don't work, no lights when activated. 4WD light not working.


Any thoughts on how to troubleshoot this?

Start with the 4WD light.
If it doesn't come on when you put it in 4WD, then jumper across the plug at the switch.

 

[Rut Row]

What part of that isn't happening?

No lights, no locker action. The issue is no power to the switch.

Start with the 4WD light.
If it doesn't come on when you put it in 4WD, then jumper across the plug at the switch.

you didn't read the whole post did you. I did that and it worked that way then the next time it didn't.

 

[Rut Row]

You may have other problems.
I don't think the locker switches even need power to work.
My override mod switches don't.

the wiring diagram clearly shows power to the switch. It all starts there. I agree, there is likely other issues at play as well.

 

[Rut Row]

I have no idea why the problem started, or what I did to fix it, but the problem has gone away and the lockers function as designed. I'm guessing it was a slightly loose connection or ground.

I still have voltage on both sides of the fuse holder with the fuse removed. I guess I'll just have to wait for something to quit working so I can find the problem.

 

[dbbd1]

I'm confused why you think one side of the fuse should be at 0V? There should be minimal drop across the fuse (both sides should be around 12.xV.

Just to add some clarity, the fuse is good if-

If measuring across the fuse, it should be 0v.

Or

If measuring from each side of the fuse to ground, it should be 12v (provided that the circuit is "on").

 

[Rut Row]

Just to add some clarity, the fuse is good if-

If measuring across the fuse, it should be 0v.

Or

If measuring from each side of the fuse to ground, it should be 12v (provided that the circuit is "on").

agree. But in this case, with the fuse removed and measuring voltage on each side of the fuse slot, one side should be 0 and the other battery voltage. That isn't the case on this particular fuse. I think that means there is a short somewhere .