Operation CHARM
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Chevy Truck
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1990
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Suburban 1/2 Ton 2WD V8-454 7.4L
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Repair and Diagnosis
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Powertrain Management
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Fan Request
Fan Request
Displays status of A/C fan control switch. Should read "yes" when A/C fan switch is in on position or when A/C system pressure exceeds calibrated value; "no" at all other times.