1996/04/15 Caterpillar

768C (02X),
772B (64W),
776C (2TK) Off-Highway Tractors;
769C (01X),
771C (3BJ),
773B (63W),
775B (7XJ) Trucks

Electrical Connections

Check the electrical connectors/plugs of the water temperature sensor and the pressure regulating valve in the electrical system that controls the variable speed fan clutch. These connectors/plugs are water resistant, but they may become contaminated as a result of high pressure washing. The contamination may cause a loss of electrical continuity through the connector contacts. Before replacing sensors or valve, try cleaning the electrical connections with a "no residue electrical contact cleaner" to see if electrical continuity can be restored.

101-0329 Solenoid Valve Assembly (Pressure Regulating Valve)

If the lock nut (X) is not tightened, the valve body (Z) may rotate in the solenoid. This could result in the three oil lines that are connected to the valve being installed incorrectly.

(VALVE SHOWN MOUNTED ON LEFT SIDE OF ENGINE) 101-0329 Solenoid Valve Assembly. Electrical Connector (W). Lock Nut (X). Solenoid (Y). Valve Body (Z). Normally Closed Port (NC). Common Port (COM). Normally Open Port (NO).

The illustration identifies ports on the valve assembly. The Normally Open (NO) port is on one end of the valve body (Z). The Common (COM) and Normally Closed (NC) ports are on the sides of the valve body (Z).

NOTE: The valve body has "NC", "COM", "NO", and arrows stamped on one side of the valve body. However, these stampings may be painted over.

Be sure the three oil lines that are connected to the solenoid valve are connected as follows:

* The oil supply line from the engine is connected to the (NO) port.

* The solenoid valve controls the amount of oil supplied to the clutch from the (COM) port.

* Any oil not directed to the clutch is returned to the engine oil sump from the (NC) port.

If the (NC) and (COM) ports are not positioned as shown:

1. Remove the three oil lines from the valve ports.

2. Loosen the lock nut (X).

3. Rotate the valve body (Z) until the ports are positioned as shown.

4. Tighten the lock nut (X).

5. Connect the three oil lines.

This will put the stampings on the valve body next to the engine block.

Fan Clutch Assembly

Because of the need for a press to remove and install some components, and the need to maintain cleanliness of the components, it is recommended that the fan clutch assembly be taken to a shop for disassembly and assembly.