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Well, this evening I will be replacing the water pump on my 2004 Chevy Express van. First thing that we have had to replace since we bought it new. It has the 5.3L V8. It does not look all that hard other than the water pump being one of the largest I have ever seen...LOL.

Now to what this post is supposed to be about. My A/C does not seem to be working well right now on the same vehicle. I checked the charge with one of those do it yourself refill kits I had laying around. The pressure looks good according to the gauge, but when the compressor kicks on, it build pressure on the low side and builds a lot of it. Then the compressor kicks off, the pressure drops down, then it does the same thing, over & over & over. I have a set of service gauges, but am unsure how to use them. I have been reading on line trying to figure them out. Is anyone familiar with these? It has two gauges and they attach to both the high & low side. What should the pressures be? Keep in mind that this van has the front A/C controls and the rear blower fan controls on the dash. The passengers in the back do not have controls and can not adjust the temp.

This is the set I have.

http://www.harborfreight.com/cpi/ctaf/disp...temnumber=92649
 

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I'm no expert, but that sounds like it's a little low on 134.

The gage pressures very greatly with temperature, so there are no absolutes I've been able to figure out.

As long as you current high-side reading isn't way over 200, I'd say go for it and put in another can.

If someone else knows better, please spill the beans!
 

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I agree low on freon. I have a Chevy Blazer. When the A/C is not cold enough I put in as much freon as it will take using the freon with a gauge attached to the can. The cycling of the compressor will be reduced as the freon charge is increased. Probably not kosher from a professional mechanics viewpoint but I have done this for years with no problems and saved hundred$ in the process.
 

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The fact that your a/c system is cycling on an off quickly is a sure sign of low freon. The low side should show around 30psi when the system is operating with the proper amount of freon. This pressure equates to about 35 to 40 degrees outlet temp. As the low side pressure drops below 30psi the compressor will cut off to prevent evaporator freeze up. Keep the fan speed on high when attempting to add freon.
 

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QUOTE(wrenchman @ Aug 12 2009, 09:48 PM) <{POST_SNAPBACK}>The fact that your a/c system is cycling on an off quickly is a sure sign of low freon. The low side should show around 30psi when the system is operating with the proper amount of freon. This pressure equates to about 35 to 40 degrees outlet temp. As the low side pressure drops below 30psi the compressor will cut off to prevent evaporator freeze up. Keep the fan speed on high when attempting to add freon.
Yep, unless your cycling switch is fried from the original low freon problem. I've has that happen, refill the freon and find out the switch got cooked. Not common but watch for it if you recharge and the compressor doesn't run after the charge.
 

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Ive always steered away from the 134 with the "stop leak" as Im afraid it will clog the dryer/filter or somehow clog up the evaporator core.
 

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Glad you got this fixed.

I was concerned about the comment "The pressure looks good according to the gauge, but when the compressor kicks on, it build pressure on the low side and builds a lot of it. ". The LOW side should NOT build pressure, in fact it should LOWER pressure when you start the engine and start the A/C. It should drop from somewhere around 50 or 60 down to 30 ish (but all these pressures ARE dependent on outside and inside temperature, so only go with RELATIVE readings!). The HIGH side is the one that should build pressure, starting somewhere around 50 or 60 and go up to above 150 (again, dependent on outside and inside temperatures).

If/when you ever do get around to using your gauges, make sure you purge them of outside air (and moisture) before you try to charge a system, otherwise you will be injecting moisture into the system which will make it become very inefficient very quickly.
 
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