Cycling Air Conditioning

My 1996 Ford Windstar air conditioner cycles on and off and doesn't get cold. I bought some pressure gauges and with the air condtioner off the high and low sides read about 70 psi. When the air conditioner clutch engages the high side goes to about 95 and the low side drops to about 18 and then the clutch disengages. Any ideas what the problem is?

Thanks for any advise you have.

You are low on refrigerant most likely. IIRC, the low pressure is typically 25 - 40 psi, when the ac is working ... but it also depends on what the ambient temperature is. There are charts available with this info.

Some refrigerant cans come with the temp/psi charts printed on the can side.

AUTO ZONE sells a DIY kit with sealant and 2 cans of compatable refrigerant with an installation kit that is cheaper than a garage and takes about 5 minutes to install. This will only work if your system is in good shape ( no holes or major leaks). The car I did had a minor leak at the "O" rings. This stuff sealed it up and The refrigerant made everything cool again.