filling your a/c system

Hey guys,
Backstory:
Last year I did some work on my a/c system in my 99 xj. I changed out the accumulator, compressor, and I think the low pressure side tube (where the orifice filter is embedded). I had all of the refrigerant sucked out which sucked (pardon the pun) since the system had a grand total of 2 oz in it ($60). After I installed the parts, I took it back and had them vacuum it and fill it (another flippin $120). The system work fine for a couple of weeks until my wife tells me it stopped. I pop the hood and low and behold, the tube I installed popped off the firewall side, thus emptying the system. I was quite mad at this turn of events and probably should have taken it back to the guys who filled it but didn't.
A year later, I'm in the same position. It had dropped off my priority list due to colder temperatures, final college semesters, and my wedding.
Today:
Bottom line is, I've got a 99 xj with no a/c entering the hottest months of the year. I bought some cans of refrigerant, oil, and a filling hose from AutoZone hoping to fill the system myself but the clutch on the compressor will not engage. Can someone help me or direct me to fix this?

Thanks so much,
Jeremy

The compressor will not engage if there is not enough freon. It's the low pressure switch-you can jump its two spade terminals together to turn the comp on-but do not run it without oil or refrigerent for very long or it will sieze.

If you've repaired the leak, you should pull a vacuum on it. If not, just add it. Use the low pressure port (not high, but yours wont fit onto the highside anyway)

Do you have a gauge for the pressure or..

89CherokeePioneer said:

The compressor will not engage if there is not enough freon. It's the low pressure switch-you can jump its two spade terminals together to turn the comp on-but do not run it without oil or refrigerent for very long or it will sieze.

If you've repaired the leak, you should pull a vacuum on it. If not, just add it. Use the low pressure port (not high, but yours wont fit onto the highside anyway)

Do you have a gauge for the pressure or..

Click to expand...

Thanks for the reply. The leak was when the hose popped off. I secured the hose with the hose fitting tool when I found it off last year. Do I need to vacuum out the system? I have no clue as to how to do that myself. Also, the crappy fill kit I got from autozone has a guage on it and yes it only fits on the low side (max 60 psi).

-Jeremy

Harbor frieght has the vacuum pump-or you can take it a shop. It _should_ be vacuumed to remove any moisture from the system. It's pretty basic, it attaches to the pressure port and will hold it at -30 or something for a half hour-if it can't or wont hold vacuum for that long then you have to find the leak.

You could simply skip that and just attach it to the ports. Basically, you want to have the A/C switch on and add until AZs gauge is in the green-maybe a little more based on vent temperature. The Compressor should engage after 1oz or 2 is added.

Edit:The problem with not vacuuming it is that if there is enough moisture it could reduce the effectiveness of the oil and damage/destroy the compressor-similar to having anti-freeze in an internal combustion engines oil.

Ive done this myself. The compressor wont engage until it has enough freon to keep it from locking up, so you will have to hot wire it over the switch. I myself just took some wire and spliced into the hot side, took the 2nd end of the wire and clamped it into my 3 bladed pocket knife...then took 1 of the blades and notched it into the low side of the switch wire. Make sure to have the freon hooked up at this point so it will start to draw it out of the can...best was to tell when you're getting full is to just have someone feel when the air is nice and cold...you can always tell when it is overfilled because while driving (i believe anyways) your XJ will begin to run hot and possibly overheat.

89CherokeePioneer said:

Harbor frieght has the vacuum pump-or you can take it a shop. It _should_ be vacuumed to remove any moisture from the system. It's pretty basic, it attaches to the pressure port and will hold it at -30 or something for a half hour-if it can't or wont hold vacuum for that long then you have to find the leak.

You could simply skip that and just attach it to the ports. Basically, you want to have the A/C switch on and add until AZs gauge is in the green-maybe a little more based on vent temperature. The Compressor should engage after 1oz or 2 is added.

Edit:The problem with not vacuuming it is that if there is enough moisture it could reduce the effectiveness of the oil and damage/destroy the compressor-similar to having anti-freeze in an internal combustion engines oil.

Click to expand...

Okay, is this the vacuum you'd recommend? http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96677 How do I know what pressure and for how long to vacuum it out for?

Ive done this myself. The compressor wont engage until it has enough freon to keep it from locking up, so you will have to hot wire it over the switch. I myself just took some wire and spliced into the hot side, took the 2nd end of the wire and clamped it into my 3 bladed pocket knife...then took 1 of the blades and notched it into the low side of the switch wire. Make sure to have the freon hooked up at this point so it will start to draw it out of the can...best was to tell when you're getting full is to just have someone feel when the air is nice and cold...you can always tell when it is overfilled because while driving (i believe anyways) your XJ will begin to run hot and possibly overheat.

Click to expand...

This sounds great. Thank you both for the replies!
-JeremyVnc

Never heard of the whole engine running hot/overheating from too much freon.....not saying it's not possible, just that i've never heard of it, and dont see how that would make it run warm...

If you do put too much in there, it will blow hot, just like it would if you don't have enough in.....the tricky part of recharging the a/c.

Jeremyvnc said:

Okay, is this the vacuum you'd recommend? http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96677

Click to expand...

No. That's a piece of crap. Even if your has a compressor that could sustain 90-psi at [FONT=arial, sans-serif]4.2 cfm, [/FONT]it isn't going to pull enough vacuum to get the moisture out of the system. http://www.aircondition.com/tech/questions/38/

Now this would do the job. http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=98074. Anywhere around you rent vacuum pumps?

Jeremyvnc said:

Okay, is this the vacuum you'd recommend? http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96677 How do I know what pressure and for how long to vacuum it out for?
-JeremyVnc

Click to expand...

Actually, that's the one I have. I was able to pull to 29" of vacuum. However, my compressor is rated at 9.1 cfm @90psi. I ran to 125 psi.

I also dissected the pump and cleaned and resealed the connections inside.

I let mine sit for just over an hour to test for leaks as well as ensure any residual moisture boil off. It's been over a month and all is well.

You will need compressed air, or about 1.5 HP air compressor to operate that style vacuum pump.

Since the hose came off, it emptyied the R-134a out, and it now has air and water vapor in it.

How long was that hose disconnected?

If it was off for many days, or longer you should replace the dessicant filter dryer again, as the one that was open to the atmosphere for any longer than a day or two on humid days, would be used up, saturated with water vapor.

Why did the hose pop off? What is to keep it from poping off again? Was it the high pressure or low pressure hose?

Two 12 oz cans should be a perfect fill, but I would use a can with at least 2 oz of PAG oil first, as you may have lost some oil when the hose blew off.

How did you handle the oil when you replaced the compressor? Did the new compressor already have oil?

I see lawsoncl posted while I was writing.

Lawsoncl,

I have seen AC profesional shops in Houston using that $10 venturi vacuum pump day in a day out on dozens of AC systems every day. That said, I agree it is not the way to go. Nice price on that little guy at Har. Frt., I had not seen it before. I have a $2000 lab vacuum (if I want to really get serious, LOL) and a 1 hp industrial AC vacuum. Anyway, like Lawsoncl says buy a real vacuum pump, at $70 you can't beet it, pays for itself in one AC job, then also buy a real gauge set. Harb. Frt. has them frequently on sale for $39.95. Then buy your own R-134a, 12 oz. can, for about $7 a can, $14 to fill an empty system!!!!!

By the way, lawsoncl, I was told recently that both the R-134a oils are hygroscopic!!! They literally suck water out of the air into the oil if the oil is left open and exposed to the air.

Ecomike said:

By the way, lawsoncl, I was told recently that both the R-134a oils are hygroscopic!!! They literally suck water out of the air into the oil if the oil is left open and exposed to the air.

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PAG stands for Polyalkylene Glycol, so it's not really an oil in the petroleum product sense. Really it's closer to brake fluid and slowly breaks down into acids under long term exposure to water. Hence the need for a deep vacuum to make sure you get all the moisture out.

Wow, this conversation just got deep. Anyway, thank you all for your replies and helping me out with this. I'm going to give it a go this weekend.
-Jeremy

okay so I got the system vacuumed out but am having trouble putting r134a in. The compressor will not engage. I tried to jump the pressure switch with a quick jumper (from one pin to the other and no go). Can someone help me here?

-Jeremy

[edit] stupid double post.

Did you charge it while it still had vacuum on it? It should have drawn in enough to exceed the low pressure cut off.

Follow the wire coming from the clutch until you find the disconnect. Pull it apart and jump the clutch side directly to the battery.

Does yours have a service valve on the compressor acess ports that is closed?

The older ones have service valves on the compressors where the hoses attach, that are normally closed, that must be opened like a water valve to add or remove refrigerant.