What are these things under my Wrangler TJ's battery?


Staff member
I was working on my 2005 TJ, and pulled the battery out. Under the battery there were two things that caught my eye:

1. the battery plate has what appears to be a pressure switch. Is that what it is? I'm guessing it cuts power if the battery "escapes" it's tray. Is that correct?

2. under the tray, there is a box with what appears to be a vacuum line coming in, but nothing else. It's bolted to the fender. I have no idea what this is.

Can anyone ID this stuff?


That?s Joe and Frank.

That ?pressure switch? is a battery temp sensor. Lets the PCM know battery temp so it doesn?t overcharge when hot.

The vacuum line box is a vacuum reservoir. If removed or cracked your HVAC control will stop working. Some models had vacuum lockers that would branch off of the box.

Never look down on anyone unless you are helping them up - Jesse Jackson
I would have never guessed either of those!

The battery temp sensor has a spring on it, I assume so that it can stay pressed up against the battery. Pretty cool design.

That vacuum box on mine came loose and was the source of a rattle that took me a very long time for me to find. Like months of looking, removing things, tightening things and so on. It was very frustrating.

i hppe my 94 wrangler is a basic beast without all the cool $hit yall got.