A/C Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

75sierraclassic · 06-14-2007, 02:28 PM

Hey guys, my truck has a slow leak and about every summer I put a new can of freon in it. When I filled it this summer I ended up putting 2.5 cans in. I don't have any guauges so I'm not sure if its overfilled. The problem is when the compressor is running it blows really cold air, but that is for only 20-30 seconds. Then it cycles for another 20 seconds and it blows much warmer air. Is this a sign that it is overfilled or underfilled? What should the low side pressure be witht he compressor on if I get a set of gauges?

Slonaker · 06-14-2007, 03:03 PM

I shoot for about 25 on the low side. I'll be the first to tell you I don't know what I'm doing, though, so I hope someone who does will come in here with a better answer.

BTW, I think my system holds about 3 cans, so it sounds like you are pretty low. It may be leaking out about as fast as you put it in. Regardless, it sounds like you have a significant leak.

Slonaker

75sierraclassic · 07-10-2007, 02:39 PM

With r-134 anyone know what the high and low side pressures should be?

**Captkaos** · 07-10-2007, 03:39 PM

45 is the MAX for the low side on 134a.

75sierraclassic · 07-10-2007, 03:50 PM

I assume you mean 45 is the max for the low side. Do you know what the high side pressures should be?
Also, is this at idle or at 1500 RPM or what?

**Captkaos** · 07-10-2007, 04:59 PM

Quote:

Originally Posted by 75sierraclassic

I assume you mean 45 is the max for the low side. Do you know what the high side pressures should be?
Also, is this at idle or at 1500 RPM or what?

Yeah, sorry typo there...

Here is a pressure chart for 134a: http://www.glacierbay.com/ptchart134a.asp

75sierraclassic · 07-10-2007, 05:45 PM

Thanks for the chart, but I'm unsure how it gives a max pressure for the high side. Is it a temperature issue more than pressure?

cjracing15 · 07-10-2007, 07:29 PM

The low side reading at idle shoud be around 40-45 if is lower you will be fine if your pressure does not fall past 25 at 2000 rpm. The low pressure switch will cut out about 20 psig. The high side shoud not be any higher than 200. normal would be around 140-170. hope this helps you.If it is higer than this WASH YOUR CONDENSER.

06-14-2007, 02:28 PM	#1
75sierraclassic Registered User Join Date: Jun 2002 Location: Kansas City, MO Posts: 186	A/C Question Hey guys, my truck has a slow leak and about every summer I put a new can of freon in it. When I filled it this summer I ended up putting 2.5 cans in. I don't have any guauges so I'm not sure if its overfilled. The problem is when the compressor is running it blows really cold air, but that is for only 20-30 seconds. Then it cycles for another 20 seconds and it blows much warmer air. Is this a sign that it is overfilled or underfilled? What should the low side pressure be witht he compressor on if I get a set of gauges?

06-14-2007, 03:03 PM	#2
Slonaker Insert Witty Text Here Join Date: Oct 2002 Location: San Antonio, TX Posts: 3,415	Re: A/C Question I shoot for about 25 on the low side. I'll be the first to tell you I don't know what I'm doing, though, so I hope someone who does will come in here with a better answer. BTW, I think my system holds about 3 cans, so it sounds like you are pretty low. It may be leaking out about as fast as you put it in. Regardless, it sounds like you have a significant leak. Slonaker __________________ '86 Chevy C10 (Sold 04/19/13 ) Stock '01 Silverado

07-10-2007, 02:39 PM	#3
75sierraclassic Registered User Join Date: Jun 2002 Location: Kansas City, MO Posts: 186	Re: A/C Question With r-134 anyone know what the high and low side pressures should be?

07-10-2007, 03:39 PM	#4
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: A/C Question 45 is the MAX for the low side on 134a. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com Last edited by Captkaos; 07-10-2007 at 04:59 PM.

07-10-2007, 03:50 PM	#5
75sierraclassic Registered User Join Date: Jun 2002 Location: Kansas City, MO Posts: 186	Re: A/C Question I assume you mean 45 is the max for the low side. Do you know what the high side pressures should be? Also, is this at idle or at 1500 RPM or what?

07-10-2007, 05:45 PM	#7
75sierraclassic Registered User Join Date: Jun 2002 Location: Kansas City, MO Posts: 186	Re: A/C Question Thanks for the chart, but I'm unsure how it gives a max pressure for the high side. Is it a temperature issue more than pressure?

07-10-2007, 07:29 PM	#8
cjracing15 Registered User Join Date: Jan 2007 Location: Lexington, TN Posts: 1,427	Re: A/C Question The low side reading at idle shoud be around 40-45 if is lower you will be fine if your pressure does not fall past 25 at 2000 rpm. The low pressure switch will cut out about 20 psig. The high side shoud not be any higher than 200. normal would be around 140-170. hope this helps you.If it is higer than this WASH YOUR CONDENSER.



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