2001 Other Chevrolet Models Heater/Air-Conditioning Switch

JSTPLNLVLY

MEMBER
2001 CHEVROLET
4 CYL
2WD
AUTOMATIC
55,000 MILES

I have a 2001 Chevy Prism. The heater/air conditioning switch isn't working properly. It only works on HIGH. We changed the switch because AutoZone said it wasn't the fan and it still doesn't work. What else could it be?

Sunday, November 9th, 2008 AT 10:38 AM

1 Reply

DAVE H

MECHANIC
13,384 POSTS

RELAYS
Fan Relay No. 1
The fan No. 1 relay is located in fuse/relay block No. 2, in left front of engine compartment. This relay, in conjunction with A/C fan No. 2 relay, is responsible for cycling the condenser fan motors off and on. Both relays share the same power feed from the ECU-IG fuse and the same ground path. When Engine Coolant Temperature (ECT) reaches 199 °F (93 °C), the fan control switch opens and both relays are de-energized.
A/C Fan Relay No. 2
The A/C fan No. 2 relay is located in fuse/relay block No. 2, in left front of engine compartment. This relay, in conjunction with the A/C MG relay and A/C fan No. 3 relay, is responsible for cycling the condenser fan motor between 6-volt and 12-volt operation. At 6 volts, the condenser fan motor operates at half speed. At 12 volts, the condenser fan motor operates at full speed.
A/C Fan Relay No. 3
The A/C fan No. 3 relay is located in fuse/relay block No. 2, in left front of engine compartment. This relay completes a series circuit, from the condenser fan fusible link, through condenser and radiator fan motors. With all 3 relays energized, voltage is applied through A/C fan No. 2 relay, A/C fan No. 3 relay, and radiator fan motor ground.
Under these conditions, both condenser and radiator fan motors run at half speed. If high engine coolant temperature or high refrigerant pressure causes one or more relays to de-energize, the fan motor circuit is switched from series circuit to a parallel circuit. In parallel circuit, condenser fan motor runs at full speed.