What should I use to test my blower motor?

As a safety precaution you should use a fused jumper wire or a power probe to apply battery power to the blower motor. In case you’re wondering, you can create your own fused jumper wire by using an inline fuse holder that you can buy at your local auto parts store.

When to test the blower control module ( GM )?

If your multimeter still does not register battery power or Ground in the indicated blower control module connector terminals, then you have found the problem that’ s keeping the blower motor from working or functioning correctly. If power is missing from the small connector Terminal B, then you need to check to see if the underhood fuse is blown.

When does the blower motor start in a car?

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. Let’s take a look at what your test results mean: CASE 1: The blower motor ran when you applied Ground and battery power.

What happens when a blower motor relay wears out?

Without it, the AC system will not be able to circulate any heated or cooled air. The blower motor relay controls the current used to power the blower motor, and is subject to the constant on and off switching. Over time, it can eventually wear out.

How can I diagnose a blower motor problem?

If you check all the fuses and they’re good, the next recommended step is to continue diagnosis by using a test light. Even better an automotive meter to verify good power and grounds at the blower motor. I often find DIY car mechanics will skip checking the ground and move right onto parts replacement mode if they find voltage to the fan motors.

How can I tell if my blower speed switch is faulty?

Test for power at all the blower speeds by moving the blower speed switch through all positions. A faulty resistor loses power at different positions on the switch. High blower speed has direct power to the motor from the switch. If there is no power indicated on high blower speed, the problem is most likely the switch or the fuse.

Where is the fuse on a blower motor?

Locate the fuse for the blower motor in the owners/service manual. Test the fuse, with the ignition key on, using the 12-volt test light.

What can cause a blower motor to fail?

If your test reveals power going into the resister with a solid ground present and nothing coming out, a failed component becomes likely. Make sure you check the connector side for damage. These resistor modules often fail from heat stress that can melt plastic connectors.