Let's talk about air conditioning!

[Mudderoy]

Well I started a thread about radiators and I resolved my running hot on the highway issue in pretty rapid fashion. So it goes to reason that I should try it again!

I recently purchased a 1999 Jeep Cherokee. The A/C just didn't work. I was hoping that it was just low on gas (R134a) and I would get lucky charging it up and perhaps some stop leak to get it going.

I wasn't lucky. It wouldn't even hold a minimal charge.

msmoorenburg offered his a/c services so I took it out to his shop. We knew it had a bad clutch on the compressor so the plan was to pull the compressor off a 2000 XJ he was parting out.

We tried that, really simple fix, unfortunately even after a new set of "O" rings all around it still wouldn't hold a charge. It was the evaporator. Yeah that thing that you have to pull the dash out to get to.

Since the 2000 had a vacuum when we pulled the compressor we figured the evap was probably ok. The "O" rings are what usually cause the leaks. So we pulled out the evap on the 2000. Pulled the evap out of the 1999. Matt did ask if I wanted to get a new evap before we put everything back together, and I sure would have liked to do that because of all the work involved. We did call a local autoparts place and it was $129. I just didn't have the cash. I figured worse case is I'd watch what Matt was doing and get a replacement later and change it out myself.

We put a vacuum on it and it held beautifully. We charged the system but the temp measured at the center vent would only come down to about 60 degrees. My 1998 runs 40 to 44 and can go as low as 38 degrees.

Matt took it out for a drive to get some air flowing through the condenser and the temp did drop a little. I think it made it to 50 degrees. It was plenty cool for the ride home but it wasn't 40, more like 52 to 55 degrees.

So after a couple of weeks my wife told me it was running about 70 degrees from that center vent. I checked myself and the compressor was short cycling. A good sign that it was low on coolant.

I charged it up and put some stop leak in it. I couldn't get it lower than 60 degrees.

I asked Matt about why it wouldn't be getting lower than 60 and he suggested that the dryer (sp?) may have been open to the humid atmosphere and it needs to be replaced.

I'll be changing that out pretty soon, but I suspect that my leak is the evaporator from the 2000. :(

I'm going to do the dryer first then I'll tackle the dash removal and evaporator replacement. I'll change the heater core while I'm in there too!

[cantab27]

this is a very detailed write up tony...heaps of pics but...its the bolts on the fire wall behind engine that got me...

http://www.jeepforum.com/forum/f11/my-actual-evaporator-heater-core-removal-installation-thread-592844/

[4.3LXJ]

Tony, it does sound like your system is leaking off. First thing I would do is try to find a can of 134A with dye in it. Run it and then get ahold of a cheap UV flash light and shine it on everything in the dark. The leak has to be addressed first. Second, I would check to see if there was a part number change between 99 & 00 on that evap core. If so, that might explain the high temps. It would be nice to see some temps of some gauges too. Did you get a nice deep vacuum on the system before charging?

[Mudderoy]

Tony, it does sound like your system is leaking off. First thing I would do is try to find a can of 134A with dye in it. Run it and then get ahold of a cheap UV flash light and shine it on everything in the dark. The leak has to be addressed first. Second, I would check to see if there was a part number change between 99 & 00 on that evap core. If so, that might explain the high temps. It would be nice to see some temps of some gauges too. Did you get a nice deep vacuum on the system before charging?

I'll have to check it with the UV light, but I haven't seen any of the dye, with the exception of a small amount on the low pressure valve (inside) just after filling it.

What temps on what gauges? I have one of those temp gauges with the long metal probe stuck into the center console vent.

I've never done it before but msmoorenburg was happy with the vacuum we pulled on it.

[4.3LXJ]

You mentioned Mat. I thought he might have some equipment. As far as I know, this is a fixed orifice system. That is unless you have a block looking thing next to the firewall. When you do a fixed orifice system, you charge it by what it shows on the gauges. They read in psi and temperature. So you know what temp the coils are operating at. Basically it is like this, if it is overcharged it will get colder but if you continue overcharging it it will warm up because not all the refrigerant evaporates. It is the evaporation that makes it cold. If you pulled a vacuum, did Mat use some gauges when doing so?

[msmoorenburg]

You mentioned Mat. I thought he might have some equipment. As far as I know, this is a fixed orifice system. That is unless you have a block looking thing next to the firewall. When you do a fixed orifice system, you charge it by what it shows on the gauges. They read in psi and temperature. So you know what temp the coils are operating at. Basically it is like this, if it is overcharged it will get colder but if you continue overcharging it it will warm up because not all the refrigerant evaporates. It is the evaporation that makes it cold. If you pulled a vacuum, did Mat use some gauges when doing so?


Yes the system is a fixed orifice system. The system was charged by the superheat formula. I could have done it by weight but my tank is empty in the robin-air system. I wish it was the expansion valve system since they tend to get way colder/faster.

[4.3LXJ]

Super heat is the way to go. I wonder if that evap core is the correct one? Too much fan/air flow maybe?

[msmoorenburg]

Super heat is the way to go. I wonder if that evap core is the correct one? Too much fan/air flow maybe?

they looked the same (didn't verify part numbers) his was a 99 and the parts jeep was a 00

[4.3LXJ]

The rule is in high humidity areas you can go a bigger evap core because of humidity. But if you charged with super heat I am kind of wondering if the btu of the coil is too small for the air flow. That would account for the higher temps with a proper charge. I am not sure where you would look to find out about that.

[Mudderoy]

The rule is in high humidity areas you can go a bigger evap core because of humidity. But if you charged with super heat I am kind of wondering if the btu of the coil is too small for the air flow. That would account for the higher temps with a proper charge. I am not sure where you would look to find out about that.

I believe the evap has a leak, so I'll have to change it anyway.

[saar]

While replacing the evaporator core, take a lot of pictures and mark each part, remember to disconnect the battery and be careful with the airbag.
It is a lot of work, if you have any questions, feel free to ask here/pm, I did that few years ago.
Saar.

[4.3LXJ]

Also if you haven't checked it already, Saar suggested cleaning the condenser coil. I have done that to a number of systems and it really does make a difference.

[ike]

FWIW…I was chasing a/c leaks on my 98 too.
I found all of my leaks have been at the o-rings.
I have a big generic assortment kit of a/c o-rings for 134-a.
It took me awhile to find out that they were what were causing my leak. They would hold for awhile then start leaking again at the same places.
I found the big kit does not have any o-rings of the correct size, close but not correct.
I wound up buying an o-ring kit for a Cherokee. They seem to be the correct size as I was replacing the leaking ones as they appeared and that has stopped my leaks.

X 2 on keep the condenser clean for good cooling.

I still have the original dryer on mine. But I have cleaned the orifice tube.

As far as super heat or by weight…I’ve done both and can honestly say I’ve seen no difference as far as cooling goes in any automotive use.
For me weight is quicker.

[Mudderoy]

FWIW…I was chasing a/c leaks on my 98 too.
I found all of my leaks have been at the o-rings.
I have a big generic assortment kit of a/c o-rings for 134-a.
It took me awhile to find out that they were what were causing my leak. They would hold for awhile then start leaking again at the same places.
I found the big kit does not have any o-rings of the correct size, close but not correct.
I wound up buying an o-ring kit for a Cherokee. They seem to be the correct size as I was replacing the leaking ones as they appeared and that has stopped my leaks.

X 2 on keep the condenser clean for good cooling.

I still have the original dryer on mine. But I have cleaned the orifice tube.

As far as super heat or by weight…I’ve done both and can honestly say I’ve seen no difference as far as cooling goes in any automotive use.
For me weight is quicker.

Hey thanks. We used the generic "O" ring kit on the 99. Maybe I should do what you did and see if my leak goes away.

[4.3LXJ]

The absolute best thing to do for AC O rings is to pull them, walk down the the best auto parts store you can find and set them on the counter and have them get their O ring box out and match them. That way you get what you need every time. I have done that several times and never thought about getting a kit.

[msmoorenburg]

Well Tony did buy the assorted pack of the proper green o-rings. I installed them with refrigerant oil on them for lubrication during the install. Tony I would get a can of dye and recharge the system and see if you can locate the leak. We did use a used a/c compressor and a used evap. So don't be to quick to rip the dash out again :D. Also a weak compressor can also cause it not to cool properly. When I charged the system the pressures were right via superheat.

[4.3LXJ]

X2 Find the leak first

[ike]

"The absolute best thing to do for AC O rings is to pull them, walk down the the best auto parts store you can find and set them on the counter and have them get their O ring box out and match them. That way you get what you need every time. I have done that several times and never thought about getting a kit."

I’ve got the same box of o-rings they have, and have never had a problem with them leaking on any other vehicle except for the xj.
After changing them several times I got an o-ring kit for the xj, no more problem.