Differential Pressure Cut-Out Switch

Differential Pressure Cut-out Switch:

The Differential Pressure Cut-Out (DPCO) Switch monitors the liquid refrigerant pressure on the liquid side of the system. The DPCO is located on the expansion valve. The expansion valve is black in color when a variable displacement compressor is used. The DPCO turns off voltage to the compressor clutch coil when liquid refrigerant pressure drops to levels that could damage the compressor. The DPCO is a sealed factory calibrated unit. It must be replaced if defective.

DPCO SWITCH TEST
The work area temperature must not be below 10°C (50°F) to test the compressor clutch circuit.

1. With gear selector in park or neutral, and park brake set, start engine and allow to idle.
2. Raise hood and disconnect DPCO switch connector boot.
3. Using a suitable jumper wire, jump across the terminals inside wire connector boot.
4. If clutch does not engage, the wiring, fuse, relay, ambient switch, or high pressure cut-off switch can be defective.
5. If clutch engages, connect a suitable manifold gauge set. Read low pressure gauge. At pressure 283 kPa (41 psi) and above, DPCO switch will complete the clutch circuit. If the low pressure gauge reads below 317 kPa (46 psi), the system is low on refrigerant charge or empty due to a leak.
6. Install connector boot on switch and repeat step number 3. If the clutch does not engage, replace the DPCO switch.