AC not working

[dougomatic]

Hi all,
I have a '93 ford explorer limited with 4.0L engine.
I replaced the head gaskets a month ago and in the process I disconnected the AC pump. I made sure the fittings were plugged so not to get dirt or moisture into the system. It was apart for one day. After reconnecting everything, I immediately recharged the system. The pressure is good but the clutch will not engage. I have rechecked the connections, pressure and electrical connections. It worked when I took it apart. I have a hard time believing the clutch would suddenly die. Is there something else I can check?
Any suggestions are greatly appreciated. It is getting HOT here in Yuma, AZ.
The temp today is 95 and by saturday it will be over 100. I don't want to replace the AC clutch unless it is nesessary.
Please help.
"Burning in Yuma"
Doug

 

[shamaal]

FWIW, next time you replace the heads, you can just loosen the A/C compressor and lines and fold it back out of the way without disconnecting.

The compressor clutch is engaged when the low side pressure is >43.5 psi and disengages when the pressure drops below 24.5 psi. The pressure switch is located on the accumulator, right under the low pressure service port.

If the pressures are good, you can remove the connector and short with a paperclip to see if the clutch engages. If it does and your pressures are correct then the pressure switch may be bad. It can be replaced without evacuating the system.

You didn't ask, but I must point out that when the system is opened (refrigerant lines opened) the system must be evacuated to remove acid forming moisture.

 

[BrooklynBay]

Another thing I was thinking about was that maybe the system didn't draw enough freon into it since the pressure switch wasn't jumped while refilling it.

 

[dougomatic]

Thank you for the reply.
I shorted the pessure switch connector and the compressor came on. I then increased the pressure to 40psi and the compressor would come on for a few seconds, shut off, about 5 seconds later it would re-engage. The cycle repeated. I will buy another can of refridgerant and try to evacuate as I am filling. There may have been too much air left in the system. We have very dry air here (10-15% humidity) and moisture was not a concern. It holds pressure so I know the connections are good. Any other suggestions are welcome.
Thank you.

 

[BrooklynBay]

The best way to evacuate a system is with a vacuum pump prior to filling it with freon.