A/C Control switch for fan on dash?

Tiny
JAMES CASON
  • MEMBER
  • 2001 CHEVROLET CHEVETTE
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
The vehicle listed above is an Express 2500. I have already put in a new resistor for the blower fan. Fan only runs on settings 3 and 4. Can you check residence on control switch at dash for each speed setting?
Sunday, September 11th, 2022 AT 6:14 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,896 POSTS
Hi,

Is this a 2001? Also, I need to know if it is a cargo van or a passenger van.

As far as the switch is concerned, here is how it works: When a blower speed is selected, the HVAC control assembly applies voltage to the blower motor resistor assembly through the blower speed blower motor control circuit. Voltage is divided between a series resistor, a thermal fuse and the blower motor to achieve the desired blower speed. The blower motor is included in the series circuit by the blower motor supply voltage (a separate fuse) and ground circuits. The blower motor resistor then provides a pathway to ground for the blower motor.

Since it works on the two highest settings, I know a ground path is being provided for the orange wire and the light blue one. So, we need to identify the tan wire and the yellow wires at the switch. Disconnect the connector and check for continuity to ground when you test those two pins.

Let me know what you find or if you have other questions. Also, the wiring schematics appear to be different between the cargo and passenger vans.

Take care,

Joe

See pic below.
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Sunday, September 11th, 2022 AT 7:26 PM

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