Model: 1/2 ton pick-up
Engine Size: 5.7
Refrigerant Type: R134
Country of Origin: United States
I need to add freon to my truck after replacing O-rings. I have a 30LB cylinder and I read that you use the manifold gauges and I have heard that you use a thermometer to determine when the system has the correct amount of freon. Can I do this without a scale to weigh it, and I have heard that you can not go by weight either. I would like to get the AC system finished as soon as possible. I have used the small cans before but thought the 30LB cylinder would save me money because I need to add freon to my other vehicles. Thanks
Are you planning to use a vacuum pump to perform an evacuation? You must charge into a proper vacuum. You also must charge with the proper amount of refrigerant. If using 3o lb canister, you have to either use a dial a charge or an accurate scale.
Yes I do have a vacuum pump and a set of manifold gauges.
Like Dougflas said, you will either need a dial a charge or a scale to measure how much R134a has been discharged from the cylinder. Also remember that you need to flip the 30 pound cylinder upside down when you recharge. There is no stand pipe in the tank.
I do have a digital scale that goes up to 75 LBS that is made to weigh packages for the postal system so I believe it is fairly accurate.
Am I understanding that you are telling me to leave the cylinder in the upright position? Why is it safer?
Safer because you'll be charging vapor instead of liquid. If you ever saw a compressor get swamped with liquid, you'll never forget the results.
I am putting in the freon now and the ac vent temp is down to about 52 degrees with the windows open and the other vents closed with the ac on high. The out door temp is at 80 degrees and the manifold gauges are about 40 low side and 200 high side. I have added freon by the weight the best I can tell it has the correct amount but I am not sure if there is anything else I can do to make it operate any better.
The truck has been running about 20 minutes and the low side reads 35 and the high side is at 195.
Edited: Sun July 04, 2010 at 9:33 AM by BG1
The outdoor temp is between 80-85 and the low side pressure is at 46 and the high is at 245. The inside vent temp with it on high and windows open is about 55 and with the windows closed its at 60 degrees. This a black truck so that makes matters worse. Is there something else to I should do to help it cool better?
You seem to be charging by pressures. How much refrigerant is currently in the system?
From what I can tell 37oz. I understand its a 44 oz system, do you know any different? I weighed the cylinder when I started and weighed as it went in. Thanks
I list 40 ounces of R12 refrigerant.
So how much r134a? That what I used.
No way to tell it's a conversion.
Go ahead and go up to 40 oz. It should not take more than that. Did you just convert it? Those trucks have a reputation to not work very well on R-134a. The oil situation is also important.
Before adding anymore refrigerant. What are your pressures at 1500 RPM? What's the ambient temp when pressures are taken also? mk378 is correct that having as close to the OEM spec is the best for a system to survive. Unless component upgrades are done there is a good chance you will have pressure issues with a full change. If that is the case under charging can lead to a lack of oil lubrication and premature compressor failure.
I looked for a sticker under the hood and found one and it listed the capacity as 2.5lbs which would be 40oz like you said, but on this site it list Chevy full size pickup C or K series 1990-1991 as 44oz but I should have looked under the hood for this sticker first. As far as the ambient temp it was between 81-85 I have different thermometers and it ranged from 81 to about 85 the truck is black and it was sitting in the hot sun and that was about 90 in the direct sun and in the engine compartment it was hotter. The engine speed was at idle but I need to put a tach on it to see what the speed really was. I was reading on a couple of other sites and it said that you should not fill a r12 system with the amount specified for the r12 system if r134a was going to be used that only use about 85 percent of the specified amount.
I have not checked the rpm at idle yet. I did try covering the dash ac vents with tape and left the one open and put the thermometer in it with the windows open. I then checked the gauge pressures while running water across the condenser and at first the low pressure went down to 24 and the high went down to 135 with the vent temp 40 and the outdoor temp 76 the lines off the accumulator were cold the real small one from the evaporator was also cold. The lines off the compressor, low side was hot and the high side had frost on it. I tried to do this again but the outdoor temp had went up to 80 and the truck is now in the sun so the results were different, low pressure went down to 38 the high pressure went down to 165 with vent temp 59 the lines were still cold but the high side did not have the frost on it like before. I checked the fan clutch and it will not spin freely it is very stiff so I am wondering if it is bad and adding to the ac cooling problem.
I moved the truck to the shade and tried the water across the condenser again with the outdoor temp at 81. I did not let it run as long but the low pressure went down to 35 the high went down to 155 and the vent temp only down to 55 but there was no frost on the line . The water temp was 77.
Edited: Mon July 05, 2010 at 11:42 AM by BG1
The reason people say not to charge to the OEM spec is the OEM condenser can't remove the heat load. High pressures equal poor cooling. But if you fail to have enough refrigerant in the system to carry the oil you will shorten the life of the compressor. You don't need a tach you get the RPM's up to have a fast idle pressure check.
Just rev the engine somewhat above idle to simulate driving conditions, the exact rpm isn't that important. Performance always falls off at idle. When water on the condenser makes a huge difference in high side pressure, the fan clutch may be weak. If it's the original one that came with the truck it's going to be worn out anyway.
Does the last information I posted help to understand what my problem may be?
I increased the rpm and the low pressure went to 33-34 and the high went to 210-215.
Edited: Mon July 05, 2010 at 11:57 AM by BG1
Those tests were at idle, or 1500 rpm?
Edited: Mon July 05, 2010 at 11:58 AM by mk378
I never got frost on the accumulator only on the high pressure line at the back of the compressor.
I just checked the pressures at 1500 rpm and the low side went down to about 35 and the high went down to 235. I do think the fan clutch is not working like it should and this was without water being sprayed on the condenser and the outside temp 86-87 degrees.
Edited: Mon July 05, 2010 at 12:27 PM by BG1
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