Porsche 928 Workshop Manual page 302

928
Engine - Cooling
19
The output stage receives a square
signal from the control unit. The
output stage contains two mutually
independent output-stage modules
with separate protective circuits:
each module controls a separate
cooler fan.
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If a fault occurs, the cooling-air
flaps are opened to the 100% setting
and the intact fan operates at full
speed, while the faulty fan is
switched off. A check is made
approx.every 20 seconds to ascertain
whether the fault persists.
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Printed in Germany-XVII,1987 Overview
19 - 13