A/C question

GBGTEXAS

MEMBER
CHEVROLET TRUCK

2001 Chevy 1500HD, 108,000 miles, 6.0 liter

Compressor, drier, orfice tube are new. System has been flushed and evacuated for 2 hours. 28 oz. Of freon and PAG oil. Problem - a/c temperature at idle is fine (40 degrees) but rises toward 50 degrees when RPM's are raised during normal driving. Do you have any ideas? A/c is just not performing at peak performance. Thanks!

7 Replies

2CARPRO JACK

MECHANIC
11,533 POSTS

What are the pressures at idle. Then at rpm? What parts did you use? OEM? Does the compressor ever cycle?( Turn off an on)

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Sunday, July 1st, 2007 AT 8:31 AM

GBGTEXAS

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Readings at idle are:
high side - 290 on a 92 degree day. Low side - 52
With rpm's - high - 260
low - 45
I even tried to lower the freon level but I think my low side is still too high. Shouldn't it cycle between 25-40. Used a new GM compressor and it does cycle, just not in the right range. I am thinking I may have a restriction in my condensor. What do you think? Thanks.

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Monday, July 2nd, 2007 AT 8:30 PM

2CARPRO JACK

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Pressures sound a bit high. Could very well have a restriction somewhere. When does the comp cycle? Have seen the low side cycling switches go bad and make the comp cycle

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Tuesday, July 3rd, 2007 AT 7:48 AM

GBGTEXAS

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Replaced the condensor, and evacuated and put 28 oz. Of freon. This time the result was constant 50 degree duct temperature. Added more freon to approximately 33-34 oz and temperature dropped to 40 degrees constant. Head pressures were high-250, low 38-40 while driving. Problem solved. Have you ever seen this before? I was using freon from a 12 oz. Can. Could it be that those cans don't have a full 12 oz? Look forward to hearing your take. Thanks.

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Friday, July 6th, 2007 AT 10:03 PM

2CARPRO JACK

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Ambient temps can change a/c pressures as well as amount of 134a. Also sometimes a fresh system needs a little time for th eoil to circulate around the system and settle into the appropriate places. I doubt if you could ever get all the 134a out of a can, seem to me there would be a little left in it, due to the fact it has to have some amount of pressure due to the pressure in the system. Make sense to you? Anyway, glad to hear your basking in cold air again