1997 blazer ac does not blow cold...help me diagnose plz

[rosegc30]

The AC on my blazer blows but does not blow cold.
1. pulled connector off of the accumalator and jumped it with a knife blade... the compressor kicked in.
2. i then charged it to about 41-43 psi on low side..... it does not blow cold after jumping to activate the compressor or charging with 134a.

what else can i try? what other steps could i take.
Thanks in advanced!

[old_master]

Clutch cycling systems are very sensitive to the amount of refrigerant and oil in the system. An overcharged system can cause just as many problems, or more, than an undercharged system. These systems CAN NOT be charged by pressure readings. Pressure readings are used for diagnosis only. The ONLY way to know how much refrigerant is in the system is: Drain the system, evacuate the system for a minimum of 1 hour at 29" Hg. Add the proper amount of oil and refrigerant.

When the system is at rest, refrigerant pressure equalizes between the high and low sides. The pressure is approximately the same as ambient temperature. When the compressor turns on, high side pressure increases and low side pressure decreases. When low side pressure drops to approx 22psi, the cycling switch, (the one you jumped) turns off the compressor. High side pressure then decreases and low side pressure increases. When low side pressure reaches approx 42psi, the cycling switch turns the compressor on and the cycle repeats. The cycling switch maintains low side pressure at an average of 32psi. If the average is below 32psi, humidity that condenses on the evaporator will freeze. When the evaporator freezes, air can not pass through, and you get no air flow from the registers.

If you decide to correctly diagnose and repair the system yourself, you'll need an evacuator, somewhere in the $300 to $500 range. You'll also need a manifold gauge set, they run any where from $100 for a cheapie to around $250 for a decent set. We are glad to help you diagnose and repair it, but you'll need the proper tools.