Pontiac Fiero 1988 Service Manual page 1053

AIR CONDITIONING: BLOWER C O N T R O L S [
C60, MANUAL
(Continued from previous page)
• If all voltages are correct, A/C Mode Selec-
tor is operating normally. Return to Symp-
tom Table.
1. Check BRN (50) wire for an open back to
HTR A/C Fuse.
2. Replace A/C Control Head.
3. If battery voltage is present at Terminal
N but is not present at Terminal B,
replace the A/C Control Head.
CIRCUIT OPERATION
The Blower Motor is a variable speed Motor,
which runs at a speed proportional to the applied
voltage. The higher the voltage applied to the
Motor, the faster the speed.
When the Ignition Switch is in the RUN posi-
tion, battery voltage is applied to the A/C
Control Head through the HTR A/C Fuse. With
the Mode Selector in the OFF position, no volt-
age is supplied to the A/C Power Relay coil and
its contacts remain open. In any other mode the
relay is energized and its contacts close provid-
ing voltage to the Blower Switch.
With the Blower Switch in the LO position,
voltage is applied through all three Blower Re-
sistors to the Blower Motor. The blower runs at
low speed.
As the Blower Switch is moved through posi-
tions Ml and M2, the switch bypasses part of the
Blower Resistors. This allows more voltage to be
applied to the Blower Motor which will increase
its speed.
When the Blower Switch is in the HI position,
voltage is applied through the ORN (52) wire to
the coil of the High Speed Blower Relay. The
High Speed Blower Relay operates, applying
battery voltage directly to the Blower Motor.
The Motor runs at maximum speed.