Odd wiring behind dash in 98 TJ

Christoph

Christoph

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Joined
Feb 23, 2021
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68
Location
San Antonio, Texas
Recently purchased a 98' sport after years of wanting one. Bedlining the tub so took the seats out and planning on painting the panels with SEM so removed them. After taking panels off I noticed a weird aftermarket switch under the dash.

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One end of the switch runs to the back of a red/black wire on a pin connector of the climate controller.

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The other end runs through the firewall into the engine bay...

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Splices into a fuse covered in electrical tape...

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Then into what appears to be stock wiring again...

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Stock wiring runs here...

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And here at the T section you can see in the background...

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Any ideas as to what in the heck this is? All of the wires are spliced like crazy and doing funky stuff. Even the stock wires are in pretty bad shape with bare wire exposed etc.




To add additional mysteries...
There is also this one that runs from what appears to be a stock ground to the frame of the dash...

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Over to this rat's nest that came apart during inspection...

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Then into the back of another pin connector from the climate controller...

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Any guidance/advice would be incredibly appreciated. Hope I haven't bitten off more than I can chew on this, but I can't see this and just tuck it back into the panel with good enough conscience to sleep at night.
 
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Damn. That was fun following along with your story. You have quite the doozy there. Love it when I see wire nuts on a vehicle.

What I would do here is evaluate that entire mess & figure out if it replaces any of your factory wiring. Does it look like all the aftermarket stuff is ONLY tapped/spliced into existing wiring? If so I'd just remove it all & repair/insulate the factory wiring with some heatshrink or electrical tape as required.

If it looks like some of this mess replaces the factory wiring, like a factory circuit diked off with a single butt splice to lead somewhere else, then you have a whole other problem with removing it & then restoring the circuits.

Got a better pic of that switch? Is it just a single pole or a momentary or what?

Anyway congrats on the purchase. Love finding PO treasures. If you haven't already you should DEFINITELY head over to the TJ Resources Forum & download your factory manual for free. Get to know the 8W section, it has everything you need for wiring. Schematics, identifying pictures of connectors, and harness routings are all in there. If you're anything like me you'll forget to connect something when the dash goes back in & you'll have a random connector with no home.
 
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The first splice looks like it's connected to a Red/Green wire at the HVAC control plug, which is the fused 12V power for the HVAC controls. The other end looks like it's going to the dark blue/black wire? That could be the AC compressor clutch. Looks like they bypassed the A/C compressor clutch relay with that toggle switch?

The 2nd circuit, that ground is for the factory stereo, and it looks like it's going to a plug for a stereo, are you sure it's climate control plug? Is there an aftermarket stereo installed?
 
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Tangerined said:
The first splice looks like it's connected to a Red/Green wire at the HVAC control plug, which is the fused 12V power for the HVAC controls. The other end looks like it's going to the dark blue/black wire? That could be the AC compressor clutch. Looks like they bypassed the A/C compressor clutch relay with that toggle switch?

The 2nd circuit, that ground is for the factory stereo, and it looks like it's going to a plug for a stereo, are you sure it's climate control plug? Is there an aftermarket stereo installed?
Click to expand...
You beat me to it, I was looking at the wiring diagrams & saw the same. Maybe the PO had a problem with the heater control switch & rigged the AC compressor himself?

Edit: I thought that was the alternator in his pic, but you're right that looks like it goes to the compressor.
 
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Tangerined said:
The first splice looks like it's connected to a Red/Green wire at the HVAC control plug, which is the fused 12V power for the HVAC controls. The other end looks like it's going to the dark blue/black wire? That could be the AC compressor clutch. Looks like they bypassed the A/C compressor clutch relay with that toggle switch?

The 2nd circuit, that ground is for the factory stereo, and it looks like it's going to a plug for a stereo, are you sure it's climate control plug? Is there an aftermarket stereo installed?
Click to expand...
You're entirely right, brain is a bit dead after today. The 2nd circuit is going to a aftermarket stereo that was installed. Not concerned with it then so there's one less thing to figure out. Plan on installing a bluetooth sound bar and not having radio in the dash.

You're also likely right on the switch having to do with the AC. Hope I didn't dig myself in too deep here, looking at some of these diagrams isn't as paint by picture as I had hoped. And if they bypassed something in the AC circuit that would definitely be over my head with what knowledge I currently have.
 
qslim said:
Damn. That was fun following along with your story. You have quite the doozy there. Love it when I see wire nuts on a vehicle.

What I would do here is evaluate that entire mess & figure out if it replaces any of your factory wiring. Does it look like all the aftermarket stuff is ONLY tapped/spliced into existing wiring? If so I'd just remove it all & repair/insulate the factory wiring with some heatshrink or electrical tape as required.

If it looks like some of this mess replaces the factory wiring, like a factory circuit diked off with a single butt splice to lead somewhere else, then you have a whole other problem with removing it & then restoring the circuits.

Got a better pic of that switch? Is it just a single pole or a momentary or what?

Anyway congrats on the purchase. Love finding PO treasures. If you haven't already you should DEFINITELY head over to the TJ Resources Forum & download your factory manual for free. Get to know the 8W section, it has everything you need for wiring. Schematics, identifying pictures of connectors, and harness routings are all in there. If you're anything like me you'll forget to connect something when the dash goes back in & you'll have a random connector with no home.
Click to expand...
It's a single pole on/off. Looks like everything is just spliced but I should probably let my brain rest and re-evaluate tomorrow with fresh eyes. Definitely excited to have it, and looking forward to the project portion of getting her where I want her, but auto wiring testing me. Guess I'll look at it as an opportunity to learn another skillset rather than a cluster #)@!*$ I don't want to deal with lol.
 
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Christoph said:
You're entirely right, brain is a bit dead after today. The 2nd circuit is going to a aftermarket stereo that was installed. Not concerned with it then so there's one less thing to figure out. Plan on installing a bluetooth sound bar and not having radio in the dash.

You're also likely right on the switch having to do with the AC. Hope I didn't dig myself in too deep here, looking at some of these diagrams isn't as paint by picture as I had hoped. And if they bypassed something in the AC circuit that would definitely be over my head with what knowledge I currently have.
Click to expand...
It looks like they were using that switch to turn the AC on and off instead of having the PCM control the AC compressor relay. Perhaps there's an issue with the A/C pressure switches that prevent the PCM from turning on the AC and they rigged that up to bypass it.
 
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qslim said:
You beat me to it, I was looking at the wiring diagrams & saw the same. Maybe the PO had a problem with the heater control switch & rigged the AC compressor himself?

Edit: I thought that was the alternator in his pic, but you're right that looks like it goes to the compressor.
Click to expand...
Possible that the switch was to kill the compressor cycling which it does with the AC off. Lots of folks have bragged about doing that.
 
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Suspicions have been confirmed. Switch is going from 12V to AC compressor clutch. Here is quick snapshot of the beautiful connection hiding behind that electrical tape under the hood.

IMG_0935.jpeg


So something is causing the compressor clutch relay to not work, and based on the repair manual qslim was kind enough to guide me towards it has to be one of these...

The compressor clutch engagement is controlled by several components: the heater-A/C mode control switch, the low pressure cycling clutch switch, the high pressure cut-off switch, the compressor clutch relay, and the Powertrain Control Module (PCM).
Click to expand...

The relay is still inside the power distribution center, so nobody removed it. Guessing it's one of the pressure switches? Will have to dig into how to troubleshoot that tomorrow.

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mrblaine said:
Possible that the switch was to kill the compressor cycling which it does with the AC off. Lots of folks have bragged about doing that.
Click to expand...
What is the claimed advantage of doing that? I don’t get it.
 
mrblaine said:
Something like that, you know, because you want as much evaporated moisture possible in the cab.
Click to expand...
Always makes me wonder about folks who do stuff like this. I was a Honda/Toyota/BMW tech for a spell & saw lots of dumb stuff. Like the spinny things in the throttle body to “speed up air” or whatever. There are folks with literal PhDs who design automotive systems with very specific requirements, it’s weird that some folks think doing stuff like this is breaking some new ground that career design engineers never considered.
 
Christoph said:
Welled up a little tear of pride when I saw it.

Probably going to well up a few more trying to figure out how to fix it... lol.
Click to expand...
Are you going to change the heater core/evaporator while you have it all apart?
 
qslim said:
Are you going to change the heater core/evaporator while you have it all apart?
Click to expand...
Not sure. It blows cold when that switch bypass is on.


Bypassed the low pressure switch... doesn't work.
Bypassed the high pressure switch... doesn't work.
Jumped the compressor clutch relay... works.
However, when I switch the horn relay (that works) with the AC relay... doesn't work?

I figured if jumping the relay made it work and jumping the pressure switches didn't make it work that means a bad relay. But the good relay from the horn didn't do the trick?

Any thoughts?
 
Christoph said:
Not sure. It blows cold when that switch bypass is on.


Bypassed the low pressure switch... doesn't work.
Bypassed the high pressure switch... doesn't work.
Jumped the compressor clutch relay... works.
However, when I switch the horn relay (that works) with the AC relay... doesn't work?

I figured if jumping the relay made it work and jumping the pressure switches didn't make it work that means a bad relay. But the good relay from the horn didn't do the trick?

Any thoughts?
Click to expand...
I was just suggesting the heater core & evaporator since you already have the dash off. They're like $60 bucks a piece from performance radiator, guys have been having good luck with those units. It'd suck to have to do it all again later when they finally fail.

As for the relay, it sounds like you aren't getting voltage to the control side of the relay. I'd start with checking for 12v (or 5v, I'm not sure what it's supposed to be because I'm not currently looking at the diagram) there with a meter/test light, if you aren't getting control voltage then that's your problem.
 
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