8206noco.fm Page 202 Thursday, July 2, 1998 1:19 PM
SYMPTOM RELATED DIAGNOSTICS ON/OFF FAN CONTROL VERBAL COMPLAINT (continued) The operation on the pneumatic portion of the control depends on the type of fan clutch being used. r
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For the KYSOR fan clutch, the fan is DISENGAGED and allowed to turn freely when air pressure is applied to the fan clutch. A loss of air pressure ENGAGES the fan. For the HORTON fan clutch, the fan is ENGAGED and is locked when air pressure is applied to the fan clutch. A loss of air pressure DISENGAGES the fan.
The fan clutch type can be visually identified. Kysor clutches are larger than a viscous clutch and attaches from the front of the fan. Horton clutches are about the same size as a viscous clutch with the fan attaching from the rear.
When performing electrical tests, it is important to wiggle wires and connectors to identify intermittent connection problems.
The fan can engage without warning. Hands, arms and personal items can easily be entangled in belts. Keep arms, hair, clothing and jewelry clear of the fan and belts when the engine is running.
Page 202
Test 1 Checking for voltage at the fan clutch solenoid 1. Turn the ignition key to the OFF position. 2. Disconnect the engine harness from the fan clutch solenoid connector. 3. Turn the ignition key to the ON position. 4. Measure the voltage from pin A of the fan clutch solenoid engine connector to a good ground.
If 12 volts are present, proceed to Test 2. If 12 volts are not present, there is an open or short between pin A of the fan clutch solenoid engine connector and the circuit breaker, or the circuit breaker has failed. Repair the open and check the fan operation. Retest to be sure the problem has been corrected.
