I'll be in Eastern Washington for a week starting next Thursday so I got this crazy idea to try and get the air conditioning working in my '98 Jimmy. Some days, like today, I wonder why I ever try to do such things. I should just accept that Blazers leak oil and air conditioning wasn't meant to work after the first 200,000 miles. I'm nothing if not stubborn, though, and I have an amazing ability to ignore the obvious, so away I went.

Last weekend I checked out the state of the a/c system. My friend has a nice set of Snap-on a/c gauges and a vacuum pump and a flushing gun so I borrowed them and did some investigation. There was no pressure in the system. When I jumped the low pressure switch the compressor came on and the gauge pulled a vacuum on the low side. Based on that I decided the compressor was probably in operable condition. I removed the accumulator and orifice tube and flushed out the evaporator core. I replaced the orifice tube with a variable tube (a tip I discovered by reading other threads on the subject) and got a new accumulator. I replaced the o-rings on the refrigerant lines and put everything together. I put the vacuum pump on the system. The best vacuum I could pull was 26" Hg. After about forty minutes of vacuuming the system I shut off the pump and closed the valves on the manifold gauge. In ten minutes there was no more vacuum in the system.

I started looking around the system for more information. I took the hoses off the compressor and noticed there was UV dye inside the compressor. I grabbed my UV light and yellow glasses and started checking for signs of leakage. There was a trail of UV dye down the back of the compressor from the high pressure switch. I removed the compressor and drained all the oil out of it and replaced the high pressure switch and o-ring with a new one. I lubricated the o-ring before I installed it. I didn't find any signs of a belly leak. It's not the original compressor; it's an aftermarket compressor so it's been changed at some point in the past.

On further examination I looked at the condenser and it also had traces of UV dye where one of the lines comes out of it so I changed the condenser for one from a 2000 Blazer that was leak-tested by an ASE-certified technician.

I put the system back together and put the vacuum pump on it to draw it down. Again, the best vacuum I could pull was 26" Hg. Vacuum held for about ten minutes before it was back to 0.

I vacuumed the system down to 26" Hg again and put in a 12 oz. can of refrigerant with UV dye to circulate it through the system and help me find the leak. I left the refrigerant in for about an hour expecting it to leak out and leave me an indication of where the leak is. When I came back to it the refrigerant was still in the system. Static pressure on the low side was 70psi at about 70°F ambient temperature. I started up the Jimmy and let it run with the a/c on max. The low side pressure cycled between 25psi and 45psi. The high side cycled between 65psi and 85psi.

Now I'm confused. If the truck wouldn't hold vacuum why didn't the refrigerant leak out? Is there something I'm missing? Should I keep adding refrigerant until I get to 28oz.?

 

Toby going to paste what Cpt Hook sent me.

The clutch should cycle: should turn ON at 42psi and turn OFF at 22psi. High side should be around 175 to 200psi just as the compressor shuts off. As for switches.... on the back of the compressor is a switch that inhibits clutch engagement if high side [ reaches ~350psi. The only other switch is the clutch cycling switch on the accumulator. Low side pressure must be at least 42psi before the clutch will come on.

NOTE: Clutch cycle time, clutch ON and OFF times and pressures will vary greatly depending on ambient temperature, humidity, and engine cooling system condition, and especially the fan clutch.


You and I are just about at the same point, my compressor was pulling some vac but putting out almost nothing. I have a new one on the way, should arrive on Monday, will keep you posted....Jeff.

Also I found that the high switch that I have has a low end open limit and high end, so when the system is very low both switches need to be jumped.

 

Thanks for the info. If it weren't for the good Cap'n we'd all be stuck in the mud. Well, except the guys down in the desert. They'd be stuck in the sand.

I can tell the compressor isn't putting out enough high pressure. I only had about 12oz. of refrigerant so I wouldn't be surprised by that. I'm still wondering about the vacuum leak. I'm going to head out to the shop and check it and see if there's any leakage. I'm also going to get a set of new o-rings and replace the washers on the hoses going into the compressor. I'm suspicious of those.

Otherwise I await your results.

 

OK, I replaced the refrigerant hose washers at the compressor. The vacuum leak has significantly slowed. In ten minutes it only lost 4" Hg. Prior to replacement it would lose all vacuum in that time.

I bought a complete a/c o-ring kit from O'Reilly's. When I swapped condensors earlier there was one fitting for which I did not have an o-ring. I'm going to go through all the connections and make sure they all have new o-rings and then re-test.

 

I replaced the o-ring on the line from the compressor to the condenser. It held vacuum for ten minutes and then I charged it up with r-134a. It blows cold now. I'm going to keep an eye on it for the next couple days to see how it goes and if it holds the charge.

I think it's fixed but I'm not sure that *ANYTHING* on this truck is ever permanently fixed.

 

Good Man, jealous would be the word that fits!~

 

Don't worry Jeff. Something will go wrong soon. Then you can commiserate again. Besides, after lunch today I'm going to see what I can do about the massive oil leak from the block adapter. That should keep me busy for a while today.

 

well,hopefully it works. my brother recharged his saturn. he had a can left. I put it in mine for the first time (never tried my ac) and my compressor said growl growl growl growl growl. Be lucky yours is okay. mine sounded like it wanted to die.

 

Toby, when I first read your title, I was going to suggest you try a AC Pro Cool charge. You went way beyond that idea and actually are tracking down the problem leak. I tried a can of AC Pro in my 2003 and so far it has worked. But we have a lot more summer to go, so I am hoping it will last.Good luck.

 

I could have gone the AC Pro route but I actually wanted to learn something about how to fix an a/c system properly. I feel like I've learned quite a bit on this job. Now I'm ready to tackle my wife's 2000 Blazer. It needs a new compressor due to the infamous HT6 "belly leak." She'll be happy in July when I fix up her a/c.