Difficulty Charging A/C System


  #1  
Old 07-13-05, 10:16 AM
xpgm18
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Difficulty Charging A/C System

Vehicle: '96 Dodge B3500 1-ton van, 360, auto, dual a/c. (Receiver/dryer system). Other facts: elevation about 150 feet above sea-level, high humidity, ambient air about 84-84F.
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What the problem was: Evaporator and hi-side hose were leaking, and the service port on the low-side hose was corroded.
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What I've done so far: I replaced the evaporator, high and low-side lines, receiver/dryer, and for good measure, I also replaced the expansion valve while I was at it. I used new o-rings and gaskets.

I evacuated the system for 2 whole hours at near-perfect vacuum; I'm quite confident there are no leaks, no air and no moisture in the system, and no restrictions.
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Problems I have: I wasn't able to insert the freeze control probe (some call it the thermostatic switch) into the evaporator more than an inch or 2, before encountering considerable resistance (The probe was inserted several inches on the old evaporator). Now I'm worried the probe won't measure the temp correctly, especially after I read that the probe should be fully inserted.

Do I need to simply force the probe in? Or keep on trying until the probe inserts fully (while ruining the fins, of course....). Any ideas?

2nd problem: The system stopped sucking in refrigerant after about 15 or 16 ounces. (It's a 3.75 pound system). Low-side pressure kept on rising, passing 40 psig, and high-side pressure stayed under 150 psig. Hi-side hose to the condenser hot to the touch, hoses after the condenser luke-warm. Ambient air temp was 84F, vent air temp 87F. Expansion valve cool to the touch, but not freezing.

Any ideas? Could the improperly inserted probe be causing the charging problem? (I didn't look at the evaporator to see what it was doing when all this was happening last night, but I don't see how it could be freezing up. The vent temp never went below 86F).
 
  #2  
Old 07-13-05, 06:28 PM
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Try Sticking your can of refrigerant in a bucket of water upside down. That jumped my high side pressure from a relativley low 175 psi to 275 psi. With just one extra can!
 
  #3  
Old 07-14-05, 07:38 AM
xpgm18
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I can't turn the can upside down on my particular system. That would dump liquid refrigerant into the low-side line and go straight to the compressor, probably causing compressor failure.

I'm open to other ideas, though!
 
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Old 07-14-05, 09:31 AM
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The Main Trick is the water It doesn't matter much, how you need to charge. The water just keeps the can from cooling down too much. Once it has the refrigeraant will no longer come out of the can. So some warm water in a bucket should help no matter how you need to charge.
 
  #5  
Old 07-14-05, 07:05 PM
xpgm18
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Yes, I did try the warm water, that helped at first, but the when the system is stabilized, the pressure goes to 40+ psig (which is too high).

I even used a leaf-blower to send more air thru the condenser, but the pressure didn't come down one bit.

I'm rather afraid the compressor might be faulty, although it's not making any odd noises. I don't know what else would cause the lo-side to be too high.
 
  #6  
Old 07-15-05, 03:09 AM
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It is not uncommon for the low side pressure to run between 50 and 60 psi on vehicles with rear a/c you need to put more freon in before you decide if there is other problems adding just 1 pound to a system that holds 3 lbs 12 oz. is not enough, have you tried increasing rpm up to around 2000 rpm.
and you can charge any vehicle with liquid but you must only crack the low side open until you see a pressure increase of 5- 10 psi.
 
 

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