Pinpoint Test B : P0645

WARNING: This page is about a different car, the 2017 Lincoln Navigator and 2017 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may cause damage to the connector.

B1 CHECK THE VOLTAGE TO THE A/C CLUTCH RELAY

Ignition OFF.

Disconnect: A/C Clutch Relay.

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
Courtesy of FORD MOTOR COMPANY A/C clutch relay socket 1	Courtesy of FORD MOTOR COMPANY	Ground
Courtesy of FORD MOTOR COMPANY A/C clutch relay socket 3	Courtesy of FORD MOTOR COMPANY	Ground

Is the voltage greater than 11 volts?

Yes	GO to B2.
No	VERIFY BJB fuses 30 (10A) and 79 (15A) are OK. If OK, REPAIR the circuit in question. TEST the system for normal operation. If not OK, REFER to the OEM Electrical Wiring Diagram Introduction to identify the possible causes of the circuit short.

B2 CHECK THE A/C CLUTCH RELAY
- CARRY OUT the relay component test on the A/C clutch relay. Refer to OEM Wiring Diagrams Component Testing , for schematic and connector information.
Did the relay pass the component test?

Yes GO to B3.

No INSTALL a new A/C clutch relay.

B3 CHECK THE A/C CLUTCH RELAY COIL SWITCHED GROUND CIRCUIT FOR A SHORT TO VOLTAGE

Ignition OFF.

Disconnect: PCM C175B.

Ignition ON.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C175B-2	Courtesy of FORD MOTOR COMPANY	Ground

Is any voltage present?

Yes	REPAIR the circuit.
No	GO to B4.

B4 CHECK THE A/C CLUTCH RELAY COIL SWITCHED GROUND CIRCUIT FOR A SHORT TO GROUND

Ignition OFF.

Measure:

Positive Lead	Measurement / Action	Negative Lead
C175B-2	Courtesy of FORD MOTOR COMPANY	Ground

Is the resistance greater than 10, 000 ohms?

Yes	GO to B5.
No	REPAIR the circuit.

B5 CHECK THE A/C CLUTCH RELAY COIL SWITCHED GROUND CIRCUIT FOR AN OPEN

Measure:

Positive Lead	Measurement / Action	Negative Lead
Courtesy of FORD MOTOR COMPANY A/C clutch relay socket 2	Courtesy of FORD MOTOR COMPANY	C175B-2

Is the resistance less than 3 ohms?

Yes	GO to B6.
No	REPAIR the circuit.

B6 CHECK FOR CORRECT PCM OPERATION

Disconnect and inspect all PCM connectors.

Repair:
- corrosion (install new connector or terminals - clean module pins)
- damaged or bent pins - install new terminals/pins
- pushed-out pins - install new pins as necessary

Reconnect all PCM connectors. Make sure they seat and latch correctly.

Operate the system and determine if the concern is still present.

Is the concern still present?

Yes	CHECK OASIS for any applicable TSBs. If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions. If no TSB addresses this concern, INSTALL a new PCM. REFER to Electronic Engine Controls .
No	The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. ADDRESS the root cause of any connector or pin issues.