TOM WALKER wrote to ROY WITT:   
      
   Mine says the same thing. It even has 4 stages of procedures to check the   
   AC system. However, it doesn't have a procedure to check out why the   
   radiator fans don't engage as the engine temps get higher than normal   
   operating temps when the PCM detects that the system is low on freon.   
      
    TW> From the service manual of a 1998 5.7L F-car (Camaro/Firebird) here   
    TW> is the descriptio of the cooling fan controls   
      
    TW> Engine Cooling Fan Description - Electric   
    TW> The electric cooling fans are used to cool engine coolant flowing   
    TW> through the radiator. The fans are also used to cool the refrigerant   
    TW> flowing through the A/C condenser.   
      
    TW> The electric cooling fans are controlled by the PCM. The PCM controls   
    TW> the ground path for the three cooling fan relays. The relays are used   
    TW> to control the high current flow to power the cooling fan motors.   
    TW> Both fans operate together. When minimum cooling is required, the PCM   
    TW> energizes cooling fan relay #1 and both fans operate at low speed,   
    TW> since the fans are connected in series through cooling fan relay #3.   
    TW> Cooling fan relay #2 is open (not energized) and is not used for low   
    TW> speed operation of the fans. When maximum cooling is required, the   
    TW> PCM energizes all three cooling fan relays. The left fan is still   
    TW> powered through cooling fan relay #1, but is now grounded through   
    TW> cooling fan relay #3. The right fan is now powered directly through   
    TW> cooling fan relay #2 and both fans operated at high speed.   
      
    TW> The PCM will also enable the cooling fans after the ignition is   
    TW> turned off. When the engine coolant temperature exceeds 113øC (235øF)   
    TW> and the ignition is turned off, the cooling fans will be enabled on   
    TW> low speed for 150 seconds.   
      
    TW> Cooling Fans   
    TW> The cooling fans are controlled by the PCM based on the   
    TW> following inputs:   
      
    TW> The A/C system.   
    TW> The Engine Coolant Temperature (ECT) sensor.   
    TW> The Vehicle Speed Sensor (VSS).   
      
    TW> Looks like SEPERATE Functions to me controled by a combination of   
    TW> Sensors and Relays.   
    TW> ---   
    TW>  þ SLMR 2.1a þ Typo Tom strikes agaoin   
    TW>  * Origin: Fidonet Since 1991 Join Us: www.DocsPlace.org (1:123/140)   
      
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