I am new to this sight. I am on my 3rd s-10 blazer. I now have a 96 ls. I am having issues getting the a/c to work correctly. When I first bought this the a/c wasn't cooling the best so I took it to work and hooked it up to our Robinair machine. I recovered the system and pulled out 2.2 lbs. The decal says it only holds 1.14 so I figured it must have been overcharged. I recovered, drained oil and pulled a vac. I recharged to spec 1.14, but clutch only would run for a couple of seconds. I then added a little more at a time till compressor stayed running and was blowing cold. I did this at night inside a shop but when in the sun and temp is over 80 it does not cool like it is overcharged? I took it back to work recovered and put 1.14 like it calls for and then jumped the pressure switch so clutch would stay engaged but still not cooling until I added more freon. Again cools great until temp gets over 80. The machine i use at work is calibrated so I know it is accurate. Anyone have any suggestions/ideas?

 

1996 refrigerant capacity is 28 ounces, (1 lb 12 oz). The system needs the correct amount of refrigerant to operate correctly. Simply adding or removing refrigerant is NOT the answer. On a CCOT (Clutch Cycling Orifice Tube) system, there are too many variables involved that all play a part in determining clutch cycle time: Compressor condition, partially clogged orifice tube, saturated accumulator desicant, bent or damaged cooling fins on the condenser and/or radiator, humidity, ambient temperature, fan clutch, water pump, engine cooling system condition, thermostat etc etc. Excessive oil charge will also reduce A/C cooling. A/C is the removal of heat, not the addition of cold air, check those items first. Overcharging will flood the evaporator, under charging will starve the evaporator, either way, both reduce A/C cooling ability. You can upgrade the A/C system by removing the fixed orifice tube and installing a VOV, (Variable Orifice Valve). It makes a noticeable difference. Most auto parts stores stock them and cost is around $25.

 

Please explain WHAT this is , what does it do that makes a difference and WHERE this is in the system.

Thanks.

 

Originally the vehicle came equipped with a FOT, (fixed orifice tube) located in the liquid line just before the evaporator, physically located just below the accumulator at the fitting for the evaporator. The FOT allows a calculated amount of refrigerant into the evaporator through a fixed size orifice. When idling in traffic, head pressure rises, (high ambient temperature, high under hood temperature, poor air circulation) the higher pressure causes more refrigerant to flow through the orifice and floods the evaporator. When this happens, register temperature increases. The VOV is operated by pressure, higher head pressure closes the valve and restricts the refrigerant flow to the evaporator, end result, cooler register output.

 

How difficult is this to swap out? Expensive ? (Besides needing to recharge the ac system again)

 

Refrigerant needs to be recovered, take the fitting apart, remove the FOT, install the VOV and a new O ring, put the fitting back together, evacuate & recharge. Total time including refrigerant recovery and 1 hour evacuation is around 90 minutes. VOV is about $25

 

Thanks, Capt.

 

Thanks for your input. I tried to remove the orifice tube but had no luck even with a proper tool. I ended up replacing the evaporator and accumulator. After removing the old evaporator, I could see why I had no luck removing it. someone obviously had been in there before and had tore the end off of it. Anyway, it works great now! Now for my next project, removing cat and gutting it. It's coming apart inside and rattles like crazy and starting to restrict flow.