At what pressures does the A/C clutch cycling pressure switch operate?

It is normally open at or below 169 kPa (24.5 psi) and closed at or above 293 kPa (43.5 psi); it controls A/C evaporator core temperature.

What does the A/C pressure cutoff switch do?

It is normally open at or above 445 psi and closed at or below 260 psi, and is used to interrupt A/C compressor operation in case of high system pressure.

What is the purpose of the A/C clutch diode?

It absorbs the voltage spike from the collapsing magnetic field when the A/C clutch is disengaged.

Which PCM pin monitors the A/C clutch signal?

Pin 41 at connector C174 of the Powertrain Control Module, which monitors A/C clutch on/off to adjust idle speed and transmission.

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Ford A/C Clutch & Blend Door Actuator Wiring Diagram - Cycling Switch, PCM

Wiring diagram of an air-conditioning blend-door and A/C clutch control circuit

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Wiring diagram showing A/C blend-door actuator, function selector switch, pressure switches, A/C clutch solenoid and PCM with color-coded wires.

AI caption August 2008 · Photo 406 of 4867

This is a Ford factory-style wiring diagram for the manual HVAC air conditioning clutch and blend door circuit. Power comes from a 15A fuse (position 5) in the Junction Box Fuse/Relay Panel on a Hot-in-Run circuit, feeding wire 295 (LB/PK) through connector C242 and splice S222. One branch feeds the Function/Mode Selector Switch (positions MAX A/C, A/C, PANEL, OFF, PANEL/FLOOR, FLOOR, FLR/DEF, DEFROST), which passes power on circuit 348 (P) through C159F/C159M to the A/C Pressure Cutoff Switch (opens at/above 445 psi, closes at/below 260 psi), then via 441 (R/Y) to the A/C Clutch Cycling Pressure Switch (opens below 169 kPa/24.5 psi, closes above 293 kPa/43.5 psi). Circuit 347 (BK/Y) then feeds the A/C Compressor Clutch Solenoid (through the A/C Clutch Diode, which absorbs voltage spikes) and PCM pin 41 at C174, where the PCM monitors clutch on/off to adjust idle speed and transmission. Clutch ground runs 57 (BK) through S102 to G102. A second branch feeds the Blend Door Actuator (solid-state, with blend door potentiometer wires 436 R/LG, 437 V/LG, 436 R/W via C220), grounded via 57 (BK) through S202 to G200. Page references to power distribution (13-9) and grounds (10-2, 10-3) are included.

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Frequently asked questions

What fuse powers the A/C clutch circuit in this diagram?: Fuse 5, a 15A fuse in the Junction Box Fuse/Relay Panel, on a Hot-in-Run circuit feeding wire 295 (LB/PK).
At what pressures does the A/C clutch cycling pressure switch operate?: It is normally open at or below 169 kPa (24.5 psi) and closed at or above 293 kPa (43.5 psi); it controls A/C evaporator core temperature.
What does the A/C pressure cutoff switch do?: It is normally open at or above 445 psi and closed at or below 260 psi, and is used to interrupt A/C compressor operation in case of high system pressure.
What is the purpose of the A/C clutch diode?: It absorbs the voltage spike from the collapsing magnetic field when the A/C clutch is disengaged.
Which PCM pin monitors the A/C clutch signal?: Pin 41 at connector C174 of the Powertrain Control Module, which monitors A/C clutch on/off to adjust idle speed and transmission.