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A/C trouble question/help

Old 11-07-2006, 01:09 PM
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Default A/C trouble question/help

I ahve a 2000 LT, 4.3, 2x4, and the compressor clutch was always cycling every 2 secs or so. this was EVEN when all controls were in the off position. I know that a low charge would cause that, but EVEN when everything is turned off??? I finally put a 18 or 9 oz. canister in. It was just one of those cheap recharge kits fom Autozone, but it has the so-called reuseable vavle and gauge. When charged the gauge will read properly while it cycles but is STILL every couple of seconds. Now reading up on this it seems that the orifice could be the culprit. I believe that it is actually an "in line device" that slips into the evaporator after the evaporator tube is removed. Supposedly, the lower radiator hose is to be removed before the tube can be so that access to the orifice tube possible.
What I would like to ask everyone that can comment is that all that I relayed above sound accurate and is there ANYTHING ELSE that may be what is causing the problems described above? Is it possible to maybe remove the Orifice Tube without the ned to remove the lower radiator hose to take off the Evaporator Tube? I think I included all info needed but if I left out something I didn't think of for best troubleshooting available.
Thanks in advance for any and all help...
Old 11-08-2006, 01:05 AM
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Default RE: A/C trouble question/help

Nobody can give me any input on this? Swartlkk can you give it a shot?
Old 11-08-2006, 02:04 AM
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Default RE: A/C trouble question/help

Here's a rather lengthy reply for you.
It sound like you still are low on refrigerant, but it is possible that you have a plugged orifice tube. If you plan on replacing the orifice tube, you really need an a/c charging station....$$$$$$$. The system needs to be evacuated, then the oricice tube can be replaced, (after it's been lubed with pag oil) The system should be checked for leaks, vacuumed down and recharged with a measured amount of refrigerant and pag oil.
It's a job I wouldn't tackle without all the proper equiptment. A negative result could be very expensive.

***I recommend taking it in to a shop.****

The Cycling Clutch Orifice Tube (CCOT) refrigerant system is used on vehicles that are equipped with 4.3L engines. The CCOT refrigeration system cycles a compressor on and off. the cycles maintain desired cooling and prevents evaporator freeze-up. Passenger compartment comfort is maintained by selecting the following on the control assembly:

• The mode.

• The fan speed.

• The air temperature.

The refrigeration cycle is controlled by a switch that senses low-side pressure as an indicator of evaporator pressure. The switch is the freeze protection device in the system that senses refrigerant pressure on the suction side of the system. The switch is located on the low-side service fitting, which is standard for this system. The equalized pressures within the charged air conditioning system close the contacts of the pressure switch when the air temperature is between 16°-26°C (60°-80°F).

Voltage is supplied to the compressor coil switch when an air conditioning mode is selected. The compressor reduces the evaporator pressure to approximately 175 kPa (25 psi). The pressure switch then opens, which de-energizes the compressor clutch. As the pressure system equalizes and the pressure reaches approximately 315 kPa (46 psi), the pressure switch contacts close. This re-energizes the clutch coil.

Under certain conditions, cycling may cause increases and decreases of engine speed. This is a normal condition. The system is designed to maintain desired cooling, which prevents evaporator freeze-up.

The operating characteristics of the low-side pressure cycling switch provides additional compressor protection. Low-side pressures could be insufficient to close the contacts of the pressure switch under the following conditions:

• A massive leak occurs in the low side of the system.

• The orifice tube becomes plugged.

If a low charge occurs, insufficient cooling accompanied by rapid compressor clutch cycling will be noticed at high air temperatures.

When the engine is turned OFF while the air conditioning system is operating, the refrigerant in the system will continue to flow. The refrigerant will flow from the high-pressure side of expansion tube (orifice) to the low pressure side until the pressure is equalized. The equalization can be detected as a hissing sound for 30-60 seconds. This is a normal condition.

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