DESCRIPTION
This unit consists of a torque controlled clutch driven fan. The system consists of a silicone filled coupling which connects fan to pulley. Fan drive is operated by a control valve which is governed by temperature sensitive bi-metallic coil or strip. The control valve maintains flow of silicone through drive.
When cooling air temperature is low, fan drive limits fan speed. High air temperature causes bi-metallic to allow greater flow of silicone to enter drive. This increases drag between driven member and driving member, resulting in higher fan speed and increased cooling.
TESTING
- When engine overheats or insufficient cooling caused by air conditioning (if equipped) or other components occurs, fan drive and thermostatic control must be tested. Start with cool engine to ensure complete fan drive disengagement. Cover radiator grille to induce high engine temperature.
- Start engine. Operate at 2000 RPM and turn on air conditioning (if equipped). Fan noise will increase when fan drive engages. It will take 5-10 minutes for fan to engage. While operating engine under these conditions, observe temperature gauge or light to prevent overheating. If vehicle overheats, remove cover from radiator grille.
- As soon as drive engages, remove cover from radiator grille and turn off air conditioning (if equipped). After several minutes, fan drive should disengage. This can be determined by reduction in fan speed and noise. If fan drive fails to function as described, it should be replaced.
- Fan drive should also be replaced if shaft seal is leaking fluid. If noise or roughness can be felt while turning fan by hand, replace drive. Frozen unit must be replaced.
This unit is the same as the thermostatically controlled fan drive except it is not controlled by a bimetallic temperature sensitive coil. Fan drive allows fan to be driven in normal manner at low speeds while higher engine speed limits rotational speed of fan to predetermined rate. Silicone in drive housing provides more positive drive at lower speeds and allows greater slippage between driving member at higher engine speeds.
If engine overheats during low speed or idle operation, increase engine speed to about 1000 RPM in Neutral. If condition is not corrected by increasing engine speed, replace fan drive unit. All units are non-adjustable.