How To Test The Blower Motor Switch (1994-1997 Chevy S10, GMC Sonoma)

TEST 2: Bypassing The Blower Motor Switch

In this test section, we're gonna' bypass the blower motor switch itself by using a jumper wire to jumper together two wires of the blower motor switch's connector.

This jumper wire will take the place of the blower switch and depending on what two terminals we jumper together, you'll get the blower motor to produce M1, M2 or HI speed.

For this test to work, you have to make sure that the blower motor resistor is OK (not defective) and that the blower motor itself is also not defective.

OK, these are the test steps:

1. 1

   Disconnect the blower motor switch from its connector.
   
   NOTE: Leave the AC-Heater Control Panel connected to its other electrical connectors.

2. 2

   Place the Vent Mode Select Switch in any position but OFF and turn the key ON (but don't start the engine). This will power up the BRN wire of the blower switch connector.
   
   The blower motor will activate and blow in LO speed (even though the blower switch is not connected to its connector) and this is normal.
   
   If the blower motor does not run at all, see CASE 3 below.

3. 3

   Jumper wires D and A of the blower motor switch connector.
   
   Your Chevy S10 or GMC Sonoma's blower motor should run in M1 speed.

4. 4

   Jumper wires D and C of the blower motor switch connector.
   
   Your Chevy S10 or GMC Sonoma's blower motor should run in M2 speed.

5. 5

   Jumper wires D and B of the blower motor switch connector.
   
   Your Chevy S10 or GMC Sonoma's blower motor should run in HI speed.

Let's take a look at your test results:

CASE 1: The blower motor ran in the indicated speed when the indicated wires were jumpered together. This is the correct test result.

You can conclude that the blower motor switch is defective only if:

• You got an OL (no-continuity) reading in TEST 1.
• The blower motor does not run in M1, M2, or HI with the blower switch connected to its connector (and the speed is selected and the key in the ON position).

CASE 2: The blower motor DID NOT run in the indicated speed when the indicated wires were jumpered together. This test result means one of several things:

• If M1 or M2 speeds did not activate, then the most likely cause is a bad blower resistor block.
• If HI speed did not activate, then the most likely cause is a bad blower motor relay. This is a very common problem.
• If M1, M2, and HI speeds did not activate, then the most likely cause is a blown fuse or a bad blower motor relay.

CASE 3: The blower motor did not run in LO speed when the Vent Mode Select Switch was turned on. This usually means that the 25 Amp HTR AC fuse (in the fuse box) is blown and not powering up the BRN wire of the blower switch connector or the blower motor.

This fuse can get blown for several reasons but the most common one is that the blower motor is defective and drawing too much amperage (25 Amps or more). You can find the blower motor amperage draw test here:

• Blower Motor Test (1994-2003 2.2L Chevy S10, GMC Sonoma).

More 2.2L GM Tutorials

You can find a complete list of 2.2L Chevy S10 (GMC Sonoma) tutorials in this index:

• GM 2.2L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The Throttle Position Sensor (1998-2003 2.2L S10 and Sonoma).
• How To Test The Throttle Position Sensor (1995-1997 2.2L S10 and Sonoma).
• Oxygen Sensor Heater Test -P0141 (2.2L Chevy S10 - GMC Sonoma).
• How To Test the MAP Sensor (GM 2.2L) (at troubleshootmyvehicle.com).