How To Test The Blower Motor (GM 4.3L, 5.0L, 5.7L)

How To Test The Blower Motor (GM 4.3L, 5.0L, 5.7L)

Sooner or later, the blower motor on your GM pickup (van or SUV) is gonna' give up and stop working.

So, if you're having a 'no blower' problem, the first thing you should do is to check the blower motor.

This can be done by directly applying battery power to the blower motor with a jumper wire or a power probe.

NOTE: This tutorial covers the vehicles in the 'Applies To:' box on the right column (on mobile device, it's at the bottom of the tutorial). But, the test procedure (described here) applies to any type of blower motor that has one terminal in its connector.

The following blower motor diagnostic tutorials may be of help:

TEST 1: Applying Power To The Blower Motor

Applying Power To The Blower Motor. How To Test The Blower Motor (GM 4.3L, 5.0L, 5.7L)

The actual blower motor test is pretty easy, the hard part is getting to it since it's located in a pretty hard to access spot behind the glove box.

Once you're able to get access to the blower motor, you'll notice that it has two separate connectors. One connector has a purple (PPL) wire and the other has a black (BLK) wire.

The PPL wire is the one that feeds power to the blower motor and the other wire (BLK) grounds the blower motor case. This Ground is important since without it, the blower motor won't run.

As a safety precaution you should use a fused jumper wire or a power probe to apply battery power to the blower motor. You can make your own fused jumper wire by using an inline fuse holder that you can buy at your local auto parts store and insert a 30 amp fuse into it.

NOTE: If you remove the blower motor from its location to bench test it, you'll have to Ground the blower motor's metal case or the test won't work. Grounding the case is important due to the fact that the blower motor gets Ground through it case.

Alright, these are the test steps:

  1. 1

    Disconnect the blower control motor from its PPL wire electrical connector.

    NOTE: Leave the BLK wire connector connected to the blower motor's case so that the blower motor can continue to get Ground.

  2. 2

    Connect a fused jumper wire to the blower motor male spade terminal that connects to the PPL wire of the connector.

  3. 3

    The blower motor should run as you soon as you connect the other end of this fused jumper to your vehicle's car battery positive terminal.

    NOTE: If you're testing the blower motor while it's still bolted in place, you don't have to Ground it with a separate Ground jumper wire.

Let's take a look at what your test results mean:

CASE 1: The blower motor ran when you applied battery power with the jumper wire. This is the correct and expected test result and tells you that the blower motor is good.

If the blower motor is not running at all or not working in some speeds, you'll need to test the blower motor resistor.

The following blower motor resistor diagnostic tutorial may be of help (applies to 1995 to 2002 GM pickups, see the 'Applies To' box of the tutorial for specific vehicle application):

CASE 2: The blower motor DID NOT run when you applied battery power with the jumper wire. This test result tells you that the blower motor is bad and needs to be replaced.

The next subheading will show you where you can buy the blower motor and save a few bucks.

Where To Buy The Blower Motor And Save

You can find the blower motor in any auto parts store. If you're wanting the buy the original AC Delco blower motor, you can buy it online for a whole lot cheaper than somewhere local.

The following links will help you comparison shop for the AC Delco and after market blower motors:

Will the above blower motor fit your particular GM pickup? Don't worry, once you get to the site they'll make sure it fits (by asking you the specifics of your particular vehicle). If it doesn't fit, they'll find you the right one.

More GM 4.3L, 5.0L, 5.7L Diagnostic Tutorials

If you enjoyed and/or found this 'How To' article helpful, I have written several more 4.3L, 5.0L, 5.7L specific test articles. You can find them all in this index: 4.3L, 5.0L, 5.7L Index of GM Articles

Here's a small sample of the articles you'll find there:

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