Engine Size: 7.3
Refrigerant Type: 134a
I was doing some electrical testing on my ac wiring, per the oem service manual pinpoint test reference. My question: is it normal to not get a voltage reading (no 12v power) at the high pressure switch and at the ac compressor, when there is no 134a charge in the system? The wiring diagram shows 12v power first comes to the clutch cycling switch on the drier, then to the high pressure switch, then to the compressor. With my key on and instrument panel switch turned to ac "on", I only get 12v power at the first switch in the circuit. Since my ac has been empty for two years, is this normal? Meaning, the 12v power is only passed on to the next switches when the ac system is charged and operating normal? Hope this makes since. Thanks again.
99 Ford F250 Superduty with oem AC
Yes it is normal- first switch is normally open, closes at 47 psi or so-- so if no pressure in the system, the switch is open....
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
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