Motojunky

I've been working on stuff forever, but never really had a need to learn much about AC work. I've dumped the odd can of refrigerant in now and then and replaced a compressor once, but that's about it. In the case of the compressor change, I had a friend who could evacuate/recharge for me.

I now need to replace the heater core in my '99 xj and of course, will do the evap core while I'm in there. The AC system is still charged. Fortunately, I have a buddy who manages a shop who can do the evacuation for me, as I really don't want to just dump it to the atmosphere.

Once the heater core job is complete, I plan to either buy or "borrow" from AutoZone gauges and a vacuum pump to do the recharge. I'd like to learn to do it right. I've got two other vehicles that have non-functioning AC, so it may be worth my while to invest in tools & knowledge.

Is there any way a DIYer can do the evacuation? I've seen a couple of things about using an old empty propane tank, but what would you do with the refrigerant once it's in the propane tank?

dzywicki

I as in the same situation. I had done just about anything you could think of mechanically, but had never delved into the AC system. This is the setup I used.

Vacuum pump from Harborfreight:http://www.harborfreight.com/air-vac...ors-96677.html

borrowed gauge set

I already had a decent compressor.


I had to replace the condenser, but while I had it apart, I replaced all the orings. The hardest part was getting the lower line off of the condenser and one of the line sup by the firewall. I tried 3 different sets of AC tools to release those connections. Just need a lot of patience and trying the same thing many, many times.

The vacuum pump from HF is barely adequate to pull the right vacuum. If you look at the physics, it will actually get you to the full vacuum needed to boil off the moisture int he system, but it gets pretty darn close. I would get my compressor to full, then open the valve to pull vacuum. Once the compressor started running, I would shut the valve and repeat. I did this throughout the course of a day and then left the vacuum overnight to verify I didn't have a leak. All was good at that point.

The borrowed vacuum gauge set I had, still had a R12 valve for the fill so I just filled straight from the cans.

Once I had the correct amount in, I checked the high side and low side pressures via the gauges and it was spot on. One thing you will want to make sure of is that you have the electric fan running when you check pressures. My electric fan got busted in a front end collision (which is why the condenser needed replaced). The pressures will be way off without the electric fan blowing over the condenser. I was really surprised at the difference with and without the electric fan. Can't escape physics and PV=nRT. As the temperature drops across the condenser, so does the pressure.

If I were going to be doing multiple cars or didn't have a beefy compressor, I would invest in a self contained pump like this:
http://www.harborfreight.com/25-cfm-...ump-61245.html

I happen to have a HF near me so I typically go look there first.

With on of these, you can set it up and leave it overnight to pull a vacuum.

Motojunky

Thanks!

I didn't realize that the compressor based vacuum pumps were available. My compressor is probably borderline but I should be able to cycle it as you did to pull vacuum. I do have a HF nearby but I hate to go... it's hard to leave without buying stuff I don't need.

I don't want to overuse my buddy connection to get the system evacuated (by doing all three vehicles) which is why I was looking for a DIY method. Doesn't look like there's any good way - I don't want to be stuck with a container full of junk refrigerant.

dzywicki

I didn't have to deal with the evacuation since the front end collision took care of the evacuation: https://www.cherokeeforum.com/f2/reb...light=dzywicki

I did do some reading on the evacuation and saw two methods:

1. If you have empty small cans you can hook up the connector to the low side port and let the refrigerant go back into each can. Once a can is full, you close the valve on the top and go to the next one. this method requires empty cans and one valve per can.

2. I saw some people modify a propane tank.

If you have someone that can recycle it for you, I would pursue that route.

I have certainly accidentally vented refrigerant to the atmosphere a few times. Went to two different pick a parts to get different AC parts and neither of them had the refrigerant pulled out to recycle. I know, I'm going to hell for that

Know what you mean about going to Harbor Freight. I always find something that I "need/want".

diskman

Should replace the dryer/accumulator while the system is emptied. Last I checked, it's fairly cheap.

Motojunky

Wow!

Motojunky

Good point. Will do.

JeepCherokeeSport00

sorry double post

JeepCherokeeSport00

Had to replace my compressor a few months back due to bad bearing. Also changed out accumulator and orifice tube. I did a bunch of research and found some great videos. Mainly from one guy on YT named CrisFix.

Here are some video links:


I used a vacuum pump and manifold gauge set from Harbor Freight. Had a local shop evacuate the whole thing for about $20. I bought everything on Amazon.


Good luck, YMMV

dzywicki

Good point on the receiver drier. I got one from Rock auto, was pretty cheap. One problem I did encounter was one of the pressure valves started sticking/leaking part way through. I could not get the damn valve out any way I tried. That's why I ended up at the pickapart again. The one I pulled off at the pickapart had an easily removable valve, but I had to change over the pressure sensor. I never did figure out if the valve was stuck or just not removable.