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Non cooling mystery

ginnmd on Sat February 09, 2008 3:41 PM User is offlineView users profile

Year: 1996
Make: Chev
Model: C1500 P/U
Engine Size: 5.7 L
Refrigerant Type: R 134a
Ambient Temp: 72
Pressure Low: 18-55
Pressure High: 100-120
Country of Origin: United States

No cooling air out of vents. Heater works and floor and dash vents respond to switching. My system got low on 134a I suspect from slow leak. I have forgotten the initial low static reading, but I had to jump low pressure switch on accumulator to get clutch to run. I then added some 134a to the point where I now am and I'm afraid to add more without advice.

Currently:

Ambient 72 deg outside, under hood 85 or so
Static Low 100 High100
Clutch cycles on for 3 sec, then off for 5 sec, then on 3 sec, etc
Low pressure cycles from 18 to 55
High cycles from 100 to 120 max
All this at 900 rpm
Line to evaporator gets cold enough to hurt hand if held, but line out, and accumulator stay warm, and line from accumulator to compressor warm to hot.
Temp inside at center vent 75 and does not change with increase Rpm.

I realize there are many mysteries for those of us not so bright; but remember, The early bird gets the worm, but the second rat gets the cheese. Thanks for any help and advice.



Chick on Sat February 09, 2008 3:48 PM User is offlineView users profile

Going by your pressures, you are still undercharged. Only way to properly charge it is by recovering the refrigerant, pull a deep vacuum and charge the system amount back in. Add a little UV dye to aid in finding your leak, common on those are belly leaks on the compressor.. Don’t add anything other than UV dye, PAG 150 oil and virgin R134a refrigerant.. No sealers or other “magic” bullets.. Hope this helps..

Look for wet or oily residue around the seams of the compressor as shown below..


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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

iceman2555 on Sat February 09, 2008 9:12 PM User is offlineView users profile

Chick is right on the money with the undercharged advice. The evap inlet is much colder simply because of the excessive low pressure due to undercharging the system. The warm accumulator and return line to the compressor are the result of the same condition. The serious down side of this....continued operation of this system under these conditions is going to result in the complete loss of the compressor. The system must be totally recharged to the correct amount of refrigerant to facilitate the migration of lubricant thur the system and back to the compressor. The first fault will be in the thrush washer/bearings area.....the compressor will become quite noisy. Farther failures will occur with the swash/shoe area and then the unit is...basically...history.
Get the system serviced properly as soon as possible...follow Chicks advice....insure that it is properly charged....lubed.....no stop leaks...no make it cool better additives...just refrigerant....and correct lube.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

Chick on Sat February 09, 2008 9:15 PM User is offlineView users profile

BTW, if you have a belly leaker, I highly recommend the Valeo/Seltec HT6 replacement compressor. Put one on my own truck last year, and no probelms at all, cools great. Here's a pic of it running.. And the best part is "NEW" is cheaper than most remans...



Just go to Ackits.com anbd look up your truck..Can't beat that compressor in my book.....Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

ginnmd on Sat February 09, 2008 10:39 PM User is offlineView users profile

Thank you to Chick and Iceman. I know you answer many questions and I appreciate your helping me. Knowledge and experience are valuable assets to share. While we're at it, I noticed that while adding refrigerant, it seemed harder to get it in--- as I noted the low side pressure cycled from approx 28 to 55. Is that because I just tried adding for a low condition without evacuating and pulling a vacuum first? I thought it would be possible to keep adding because of the compressor suction, even to the point of excessive high side pressure if not careful. My situation seemed different in that no more refrigerant seemed "to go in". Maybe I just didn't wait long enough, but "chickened out" when the low side pressures seemed to be getting excessive. Also I've been a bit confused by some topics regarding adding oil to the system. I understand (I think) that compressors compress vapor, and liquid refrigerant going in could damage it, hence one of the protections of the accumulator. Why then can oil be put directly into the suction port, four or more ounces, or compressors shipped full of oil, and when installed and run, no damage will occur? I've probably missed something here in my understanding of all this. Thanks again. Maybe some of this will be helpful to someone else as well.

Chick on Sun February 10, 2008 6:31 AM User is offlineView users profile

It’s a simple question, but the answer could go on for pages, so for the sake of your question, the accumulator holds excess “liquid refrigerant coming out of the evaporator (O tube systems allow much more liquid thru than expansion valve systems..) and allow it to evaporate fully before going back to the compressor. It also holds oil, which “mixes” and is carried with the refrigerant. Another reason the “proper” oil must be used with each refrigerant. Sometimes liquid migrates from the accumulator and “slugs” the compressor when sitting for long periods which can ruin the compressor over time. I “believe” GM took care of that problem on the trucks with accumulators mounted in such a manner as to allow this, buy adding a bleed hole in the “J” tube within the accumulator?? Not sure, but GM Tech can elaborate on that.. Hope this helps..

Perhaps this Thread can help you understand better..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

Chick on Sun February 10, 2008 6:36 AM User is offlineView users profile

Lost sight of the charging question... Sorry... You can top off the system as long as it wasn't totally empty, but charging from a vacuum is best. If you're topping off, and you're sure the system had some refrigerant in it, charge slowly until both the inlet (after O tube) and the outlet of the evaporator are the same temp, with the outlet slightly colder and you'll have the full charge..Watch the high side pressures, and they should be around 2.2 to 2.5 times the ambient temp (factory refrigerant system) when you achieve the cold suction line.. But airflow, air in the system, etc will affect the high and low side pressures. Make sure your clutch fan is in good operating condition.. Air flow is very important..Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

ginnmd on Sun February 10, 2008 6:37 PM User is offlineView users profile

Thanks again. Better news today. I added another 12 oz of 134a (all I had on hand) and the system "came alive". Compressor now running without noise and Low side 22 and High side 155. Cooling to 40 deg inside center vent with 75 deg ambient. This can of 134a had dye, so I'll be looking for leaks. I'm still a little low by the numbers, I guess, but I expect to find leak in compressor with my usual luck. I'll certainly take your advice with the Seltec Compressor from AC Kits. My HT6 also has a high pressure switch in the back, does the Seltec have the same, or will I have to modify something? Maybe if current system lasts for a while I'll just add a little more refrig, but don't think I'll be that lucky.

Chick on Sun February 10, 2008 6:50 PM User is offlineView users profile

I cannot remember if it came with the switch, or if I had to switch it over to the new one, which is no big deal, snap ring plyers, and it comes right out.. Maybe one of the other guys can remember...Worked on a lot of compressors since last year, and can't remember my own....
But just a point, any reman compressor comes with the switch port plugged, and you have to use your old one..Since they can only warrant the compressor, and not electrical switches...

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

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