AC problem on 98 Blazer

[megapossum]

After replacing the lower intake manifold gasket, along with the plenum and valve cover gaskets, I've discovered my AC isn't cooling at all. During the above repair I unbolted the compressor and set it on the passenger side out of the way. Checked the low side pressure and had no pressure. Thought I might have loosened something and caused a leak. Hooked my gauges and vacuum pump up and vacuumed for about an hour pulling 29in. Hg. Turned off and after three hours the needle had barely moved. Decided I'd add some R134A until I got enough in to activate the clutch on compressor, read guages and try to see where I was with it. Initially I had readings of 100 on low side and only 50 on high side. I'd added about 2/3 of can of refrigerant and my clutch had activated the compressor. Turned off and checked the electrical connection to compressor which appeared okay. Honestly I didn't know what to do next. Fired up the engine again and still had the crazy reading when the compressor clutch kicked in. Actually it was doing what I think is called, "Short Cycling," on and off every five seconds or so. When the compressor was running the gauges would show fifty psi on low side and a hundred on high side. Also the sight glass on my gauges was filled with oil. Don't know what to make of what I've described and hope someone can coach me on what to do. I'd planned to put some dye in the system to show any leaks I might have, but with the way things were going I didn't get to it. This experience has shown me I've got a lot to learn about auto ac systems! Any and all suggestions will be appreciated.

[brcidd]

Your system holds 30 ounces (almost 2 lbs) you haven't put enough refrigerant in to get proper cooling- If compressor has never been changed, you can bet you have a "belly leaker" where the bottom of compressor is oily/greasy at the 3 o-rings seams. I re-seal these almost weekly, clean the sealing surfaces and install new o-rings- and all is fine. I have yet to find one over 10 years old that doesn't have a belly leaker....

[megapossum]

brcidd-thanks for the response. The compressor has been replaced once, seven or so years ago. I didn't think I had nearly enough R134A in it, but it didn't seem to be taking anymore when the compressor was "short cycling." When I unbolted the compressor and moved it there was no oily residue on the bottom as you described. Prior to doing the repair I described it was cooling well. Were the weird pressure reading I was getting due to the lack of refrigerant? At no time did it cool any. Both the accumalator and low side line got hot and stayed that way. Should I go ahead and replace the O rings as you described even though the bottom of the compressor isn't oily/greasy? BTW when I was working with it, I was outside and the ambient temperature was about 90deg.F. I had a big fan blowing on the condenser while I was trying add the refrigerant.

[brcidd]

To "make" the compressor suck in all the refrigerant- run it full time by putting a paper clip across the connector terminals at the accumulator after you unplug it- this is the evaporator freeze protection switch, sometimes called the low pressure switch.

[megapossum]

OK, jumped the switch on the accumulator and had the compressor running constantly and was able to get the balance of my first can in. Prior to starting up, pressure on both gauges was 50psi. Took nearly 30min. to get the balance of first can in. Started another then. During this time, Low Side=102-104, High Side=100. Interestingly these pressure were constant, unchanging as refrigerant was taken in. This seems peculiar as I've noticed in past to my few AC efforts there seems to be much more response to addition of more refrigerant. It seems as if I've reached an equilibrium point, as if the can of refrigerant can't overcome the low side pressure of the system and isn't flowing in. I know I'm revealing my lack of knowledge on the AC subject, but am trying to learn and I realize from your responses to my problem that you are a master on the subject. Hopefully if you don't give on me, you can guide me to the solution. Again I am thankful for the help. Please keep it coming!

[brcidd]

With engine off- does front clutch driver of compressor turn easily?, as in with one finger on it? Do you feel tiny little "catches" as you turn it by hand? If so, your compressor is "imploded"- has all the stainless steel intake valves destroyed- Check your orifice tube (connection at evaporator inlet- at bottom of evap)- does it have stainless steel fragments?

[megapossum]

Hi brcidd, following your instructions I find the front clutch plate can be turned fairly easily with a couple of fingers considering my arthritis in my hands. Turning it several times, it turned with uniform resistance and no hard stretches or succession of them. To remove the orifice tube, will I first need to remove the accumulator or just work around and under it? Never removed one. If I find evidence of an imploded compressor, what would I need to replace? Compressor, accumulator, orifice tube, and anything else? Would evaporator and/or condenser need to be flushed? Being a retiree I'm concerned about costs of what needs to be done. However as I bought this Blazer new, I know how it has been serviced etc. and guess I'll keep it. Let me know what I need to do next. Thanks.

[brcidd]

Are you using a gage set to charge with? How do you get your high pressure reading? If on a gage set- be sure the high side valve is closed, so that you are not circulating refrigerant through the gage set- this would be why you can't get refrigerant to flow in, and why the high and low side readings are identical.

[megapossum]

Hi Brcidd, your last post did the job. Hate to admit it, but after using my gauges to vacuum the system. Afterward when I started to recharge, I forgot to close the High Side valve! This caused all my problems. Glad you kept going with me. As soon as I closed the valve I was able to start charging the system again. After I got the remnants of the second can to start going in and I felt the accumulator top which was no longer real warm, I was pretty sure it was going to downhill from then on. When I finished I had a low side pressure of 45psi and measured 51deg.F inside at the center vent. It was dusk but the outside temp was just under 85deg. I had about a 30deg differential with the ambient temperature. Would have liked to have had it a little cooler, but with some more of the 95-100deg. days coming before the end of the month I'm content with that. Sorry my carelessness took up so much of your time. Was just about on the verge of removing the orifice device to check for debris from my imploded compressor! Had already watched a couple of youtube videos to see what would be involved. Thanks again for all of your advice. I usually remember these experiences better than reading about them in a book.

[brcidd]

It is hard to predict what mistakes can happen, when I don't even use a gage set- I use a recovery machine and am used to throwing valves back and forth as a second nature... So it was just a thought, when you mentioned equal pressures. Glad you got it going- but remember, you lost the refrigerant somehow- so you have a leak- your problem is only temporarily solved.

When you have a flat tire, does putting air in it fix it?

[megapossum]

brcidd, You are right about the leak. Had a can of dye that I planned to put part of in the system. When I had all the problems you helped me with, I forgot the dye. Was going to use some I'd gotten from NAPA. Has low side quick connect/disconnect and is in a pressurized can. Checked awhile ago and temp at center vent was 38deg.F with 70deg. ambient. If I can't locate my leak with the dye, I've got a electronic sniffer that I can try. Don't know how to use it very well yet. Again many thanks for all the help you gave. A good learning experience for me.