Here's a new one: Dash backlights come on-and-off as though I am putting the headlights on

[MikekiM]

There's always something...

The cluster and center stack backlights come on and the odometer dims, as though I put the headlights on, which would lead one to think it's the headlight switch, right? I happen to have a new headlight switch that I have yet to install. No amount of jiggling of the headlight switch changes the dash lights.

Here's the twist. Flip the left turn signal on and all the above happens opposite the left turn signal. No change when the directional is switched for right turn signal.

Any thoughts?

 

[hear]

Flip the left turn signal on and all the above happens opposite the left turn signal.

Can you explain this in more detail?

 

[MikekiM]

Can you explain this in more detail?

With everything as one would expect it to be normally.. all lights off, no backlights on the cluster or HVAC controls.. move the turn signal stalk down as you would when making a left turn and the cluster and HVAC backlights cycle on and off, alternating with the turn signal.

As it's getting darker I see the running lights are coming on and off too.. I'll be able to tell more in a few hours...

 

[Wildman]

It sounds like a ground issue somewhere to me. But I could be wrong. Now where to look first I have no clue other than to start at the grounds in the wiring harness near the headlights. And then work your way backwards to the dash. There is a listing of the grounds in the FSM.

 

[MikeE024]

From what I

There's always something...

The cluster and center stack backlights come on and the odometer dims, as though I put the headlights on, which would lead one to think it's the headlight switch, right? I happen to have a new headlight switch that I have yet to install. No amount of jiggling of the headlight switch changes the dash lights.

Here's the twist. Flip the left turn signal on and all the above happens opposite the left turn signal. No change when the directional is switched for right turn signal.

Any thoughts?

Yea I’d try a new switch and ensure the harness plug is good while you are in there. I had to replace my switch and plug a couple years ago.

I’ve had good results with the Napa Echilin MFS.

 

[MikekiM]

Almost comical.. Out of nowhere..

 

[MikeE024]

Well…at your headlights didn’t completely go out while merging into SF highway traffic filled with semi trucks (happened in a dually right after buying it).

I’m not going to blame this on your cluster when the MFS is known to do this nonsense when it goes bad. And I wouldn’t bury myself in the harness until I know the switch and plug are good. Just my $.02

 

[MikekiM]

Well…at your headlights didn’t completely go out while merging into SF highway traffic filled with semi trucks (happened in a dually right after buying it).

I’m not going to blame this on your cluster when the MFS is known to do this nonsense when it goes bad. And I wouldn’t bury myself in the harness until I know the switch and plug are good. Just my $.02

I'm going to replace the switch in the morning.

 

[MikeE024]

I'm going to replace the switch in the morning.

Feel free to yell at me when it doesn’t fix it.

 

[MikekiM]

Feel free to yell at me when it doesn’t fix it.

It's a fifteen minute job at most. And I have the replacement switch.
Should have just threw it in a few weeks ago but it was too cold to be working on the Jeep.

I really need a big shop, with a lift and heat..
And a fridge for beer.
and a big screen TV

 

[MikekiM]

Ok…. That did nothing. At least I can say I have replaced the 25 year old switch.

It appears all works as it should when the headlight switch is in either on position.. running lights or full on. So, until I figure out what to check next, I’m rocking DRLs.

Any ideas?

I’m kinda reaching the limit of my patience. I seem to get about two weeks of problem free diving before some new issue pops up.

 

[NashvilleTJ]

Almost comical.. Out of nowhere..

Ahhhh, that’s not a wiring problem. That thing is possessed. You need an Exorcist…

 

[hear]

The more bizarre the behavior, the more likely it is to be a grounding issue.

 

[MikekiM]

The more bizarre the behavior, the more likely it is to be a grounding issue.

I suck at navigating the FSM. Could take me a week to find the schematic of all ground points.

 

[MikekiM]

Ahhhh, that’s not a wiring problem. That thing is possessed. You need an Exorcist…

Borders on a comedy show. .

 

[Apparition]

Ahhhh, that’s not a wiring problem. That thing is possessed. You need an Exorcist…

 

[JMT]

I suck at navigating the FSM. Could take me a week to find the schematic of all ground points.

Just start looking near the headlights for a bare wire. There’s one ground there just above the engine bay side recess for the headlight.

 

[Irun]

Definitely sounds like a grounding issue. In addition to checking what others have mentioned, I just went through something similar with my sons TJ. In our case, the problem was corroded connectors for the lights on the fender flares. We cleaned them up, applied, dielectric grease, and all the weird behavior disappeared. While this may not be your problem, it's easy enough to check.

 

[MikekiM]

Just start looking near the headlights for a bare wire. There’s one ground there just above the engine bay side recess for the headlight.

This one I know.

Definitely sounds like a grounding issue. In addition to checking what others have mentioned, I just went through something similar with my sons TJ. In our case, the problem was corroded connectors for the lights on the fender flares. We cleaned them up, applied, dielectric grease, and all the weird behavior disappeared. While this may not be your problem, it's easy enough to check.

Had a ground issue with the led marker on the flare a few months back. The marker would flicker but that’s where it stopped.

I would expect problems with the headlights if the ground there was shot, no?

 

[tm dean]

Had a similar problem, a couple of weeks ago. The battery would crank the vehicle, but when it became dark the lights would go dim. then the alternater would have to charge harder to keep the headlights on but tail lights would go off. Did a load test on the battery and it was below specs. Replaced the battery and all was roses.
i do agree on the suggestion to check your grounds. Many years ago i had a 55 chevy and the grounds had gotten bad on the tail lights. When the brake pedal was applied the headlights would go out.