NV3550 Reverse Switch Short?

[Windrac]

Hi all,

First I just want to introduce myself. First post. Today is my one-week anniversary of Jeep ownership and I've been crazy busy changing fluids, plugs, doing tire service, greasing, etc, etc. I'm an electrical engineer, and I grew up on a farm, so I'm used to working on stuff. Just new to Jeeps so looking to get some more jeep-specific knowledge.

TJ specs:
2003 Sport
4.0L
NV3550
NP231
Dana 44 rear axle with LSD
~160k miles
Hard top w/ roof rack
Mostly stock

Anyhow, I'm having this awful problem where every time I shift into R it blows fuse 7 behind my glove box. This also kills my rear window defogger.

I tested the reverse light receptacles for ground shorts and didn't find any. I'm looking at the wiring diagram now, so I know roughly what to check next, just wondering if this is a somewhat common problem and the giant TJ brain accessible on this forum knows of a common short spot.

Also, where on the NV3550 is the reverse switch mounted?

Thanks all. Looking forward to being a forum member.

 

[AndyG]

Hi all,

First I just want to introduce myself. First post. Today is my one-week anniversary of Jeep ownership and I've been crazy busy changing fluids, plugs, doing tire service, greasing, etc, etc. I'm an electrical engineer, and I grew up on a farm, so I'm used to working on stuff. Just new to Jeeps so looking to get some more jeep-specific knowledge.

TJ specs:
2003 Sport
4.0L
NV3550
NP231
Dana 44 rear axle with LSD
~160k miles
Hard top w/ roof rack
Mostly stock

Anyhow, I'm having this awful problem where every time I shift into R it blows fuse 7 behind my glove box. This also kills my rear window defogger.

I tested the reverse light receptacles for ground shorts and didn't find any. I'm looking at the wiring diagram now, so I know roughly what to check next, just wondering if this is a somewhat common problem and the giant TJ brain accessible on this forum knows of a common short spot.

Also, where on the NV3550 is the reverse switch mounted?

Thanks all. Looking forward to being a forum member.

It's on the driver's side of the transmission and an offset 3/8 O2 sensor adapter is the ticket to remove it ..I went through 4 to get one that worked.

The defroster fuse blowing weirds me out , and makes me wonder if something weird is going on in back...@Jamison C is great on the TJs factory circuits.... if he chimes in he's great.

 

[mmmkam]

When I bought mine from the previous owner that switch was bad on mine too. Easy fix for about $15. No issues since.

 

[Windrac]

Hey all, finally had time to crawl under there and look at it. I was on a business trip last week.

The rear defroster fuse blowing is due to that circuit and the reverse lights being fed from the same fuse behind the glove box.

As far as the short goes... I figured it out. It's the switch like @mmmkam said. I unplugged the wiring harness and shorted it with a paper clip. Fuse didn't blow. Tested resistance against switch and ground in R... and found the problem. So I need a new switch.

And it looks like this isn't a new problem. Previous owner cut the load side of the wiring harness running to the switch and bypassed it to the other end of the wire up by the hood hinge. Seeing as there is nothing wrong with the wire itself, this obviously didn't fix the problem.

This makes me worried about what other shenanigans I'm going to find if the last guy didn't know how to use a multi-meter

Anyhow, off to find a new switch!