LobsterThief

I'll check it out -- will I need to remove any coverings down there to get to it? I'm trying to get as much information as I can first -- I'm 6'5" and contorting to work under the dash in this truck is never easy :P

When I first got my MJ it wouldn't start by turning the key -- so the PO installed a push-button start on the dash. You'd have to turn the key and then push the button to start it. 6 months into my ownership the problem fixed itself and continued working for another 6 months. The other day, while camping, I (stupidly) charged my phone with the key turned to ACC and after 20ish minutes the battery died. Got it jumped and since then I have to use the push-button to start it again. What baffles me is that this started happening after the battery died yet now it starts right up using the original method (turn key, push button) every time. Any suggestions on things to check? Thanks!

Definitely seems to be working properly now :) I'll keep an eye on it and use your troubleshooting tips if it becomes a problem again. You never know with these 20+ year old trucks. There is still a very tiny bit of water dripping onto the passenger floor from directly under the dash -- and I know the drain has been cleaned out so that's about all that's left to check.

Had a bit of a eureka moment! Dropped the bottom dash panel and saw that what I assume is the thermistor had broken from its glue and the temperature probe was measuring the cabin air rather than being seated in its hole. Glued it back to the box, gonna wait a few hours for it to cure before giving the AC a shot. Will keep you guys posted. Glue came off You can see the hole where the probe is supposed to go

My FSM disappeared during my move a few months back so I'm going to order a new one -- until it gets here I'm going to move forward with troubleshooting. I'm assuming the thermistor is device with the small wire loop mounted under the passenger side of the dash? It seems to just be stuck up under there (no longer mounted to anything), though it is plugged in. Any idea how to test the thing? I think if the compressor isn't cycling it might be responsible for freezing my lines up. I'm going to order a new LPS and try swapping it in as well. Can I change the LPS without losing coolant? I checked the door that the cold/heat slider pushes using the cable -- the controls are pushing the cable all the way (in other words, opening/closing the blend door properly). This is located on near the passenger side footwell -- is there anything that might still be keeping it from closing fully? Or another door I should check? I've noticed that though the AC gets a bit warmer after driving a few minutes, it is still a colder than the outside -- but no matter what the top left vent blows warm. Under no circumstances does the top left vent blow cold. Maybe a sign? Thanks guys!

Checked the blend air door and it's functioning properly

Here's what I've checked so far: - Checked all HVAC vacuum lines (including to the vac canister in the bumper) and they all seem to be sealed. - Checked the connections behind the HVAC controls since I removed my radio the other day and may have bumped them. They're good. - Compressor clutch engages when I turn the AC on but it won't cycle off (pretty sure it's supposed to cycle, right?) The most important thing I just noticed is that it'll blow cold when I turn the engine on and after a minute or two it starts blowing warm. If I turn it off for a bit and start it it'll blow cold and then get warm again. There is a lot of frost on the lines coming out of the block on the firewall (the lines going through the firewall into the cab). Maybe the compressor not cycling is causing it to freeze the lines up? I'm gonna check the blend air door as soon as it stops raining Edit: Just realized the vacuum line going into the heater actuator in the engine bay was broken off; I snipped the end off and reseated the vacuum connector but it didn't make any difference. This one (not a photo of mine obviously):

Hey guys, I had my AC recharged about 6 weeks ago in my 91 MJ 4.0 -- I have an AC buddy who vacuumed it and refilled it with R12 (the old stuff). He also tested the system for leaks. A few weeks ago I decided to replace the bumper vacuum reservoir (football type) that was completely missing and capped off. Around the same time, the AC started blowing warmer and warmer -- sometimes it blows slightly cool (just barely cooler than the outside temperature) and other times it blows warm. Do you think it's possible to have messed the HVAC system up (like the vac system) by replacing that canister? Or is this a coincidence? I live in Florida and it's still super hot out :ack: Any advice is much appreciated!! Thanks, Zach

Took a quick peek (once the rain had stopped) and discovered the exhaust pipe had actually ripped out of my original muffler. Replaced it with a shiny new one and now it's good to go ;) Thanks guys

This makes a lot of sense! Any recommendations on checking it (short of pulling the thing)?

Hey guys, The hurricane's passing by us (in Tampa) and last night I hit a rogue puddle at about 30. Now the MJ sounds really loud (almost like an exhaust leak) and has a definite loss of power. I haven't replaced my wheel well splash guards yet (stupid, I know) since they broke, if that's any help. What should I start pulling apart and checking? Thanks!

Will do. Will be hitting a few P&Ps with a buddy of mine in a week or so. I'll post up here if I find anything that's a match. ;) :cheers: Hey Red Did you ever run into one? Thanks! Zach

If you find one that fits, please let me know what make/model you got it from :) Been going crazy trying to find one myself!

I wish! But in Florida with an SWB. Yeah, I've seen tons on Craigslist (even free) but no luck. I can find some where the bed dimensions line up but due to the height and position of our wheel wells it's tough.

Still looking for one if anybody has one!