8206noco.fm Page 201 Thursday, July 2, 1998 1:19 PM
SYMPTOM RELATED DIAGNOSTICS ON/OFF FAN CONTROL VERBAL COMPLAINT
Figure 321 — Diagnostic Procedure Flowchart
Perform this diagnostic procedure when the ON/OFF fan drive does not turn ON, does not turn OFF, allows the engine to overheat, or the override switch does not work. This procedure should not be used for viscous fan drives or ON/ OFF fan drives which are not under V-MAC II control.
The ON/OFF fan drive is clutched using air pressure. The air pressure is controlled through an electrical circuit attached to V-MAC II. Electrically, when V-MAC II allows current to flow through the circuit the fan is DISENGAGED. When the electrical flow of current is interrupted the fan is ENGAGED. In this manner the fan is engaged if there is a loss of electrical power.
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