'97 Dodge Ram P/U 3.7L V6 A/C condensor fan won't run but the A/C clutch functions and the air blows cool when the truck is in motion. Checked the fuses and relays, all ok. Metered the connector to the fan , no voltage. My theory is that it's low on refrigerant and the pressure sensor won't allow the fan to run but why then does the A/C clutch function unless there are more than one pressure switches in the system. I did notice very short cycling of the A/C clutch, on for 3 seconds off for 3 seconds. I allways thought that if the refrigerant was too low the system wouldn't work at all. Any theorys or suggestions.

No longer works. Any ideas on how to diagnose the problem?