Got a 1997 XLT, 4.6 V8 auto, RWD. Truck has remote start kit installed in 1998. The air conditioning is barely operating. Was almost capable of making snow. Died slowly.

1. Clutch cycles in & out every 5 seconds. Only on for about a second or two.
2. Clutch pulley rotates properly.
3. Low side pressure 45-55psi
4. Replaced LP cutout switch this morning. No change.
5. Ambient air temp has been 88-95°F
6. Temp door operates properly. Heat comes out when on heat, goes away when on cool.
7. Blower works fine.

Need to know what controls the clutch relay. Is there a module behind the dashboard controls? Can a defective control module cause the rapid cycling? Pressure indicates LP switch should be on, which it obviously is. What can be interrupting the power every 5 seconds?

As I understand it, the power chain is +12 bus to control module to HP cutout to LP cutout to clutch relay to clutch.

Also, as I remember, back when it was in the last throes of good operation, during compressor ON time, there was an odd sort of low-frequency sound that came from behind the control panel. A clue to module failure?

If anyone has had this experience, please chime in. It gets blistery hot here!

 

Start with the HVAC FAQs. Link is in signature.

What is the high side pressure?

The pulley doesn't have any choice in the matter. The important thing is what the clutch hub is doing and if it's properly turning the compressor shaft when engaged.

A 97 doesn't have a clutch relay. The compressor clutch is controlled directly by the series circuit of CJB fuse F5, the mode switch, the HPCO switch, and the LP cycling switch.