My A/C clutch does not engage in my 1982 300. I'm not sure if it is due to low freon or an electrical problem. I measure 9 volts at the connector on the clutch when the A/C is turned on. This seems low. Can I apply 12 volts directly to the two terminals on the clutch to see if it engages?

If I short the terminals on the high pressure swicth, should it engage?