How To Test The Blower Motor (2001-2005 1.7L Honda Civic)

In this tutorial, I'll show you how to test the blower motor and blower motor relay on 2001-2005 1.7L Honda Civics in a step by step manner.

8 times out of 10, when the blower motor stops working, it's the motor itself that has fried but not always.

Other components that can fail, and cause the blower motor to stop working are:

• Blower motor fuse (located in the under-hood fuse box).
• Blower motor relay fuse (located in the under-dash fuse box).
• Blower motor relay.
• Blower motor.
• Blower motor resistor (known as the power transistor).

With this tutorial's, you'll be able to test them all and get to the bottom of the problem.

NOTE: If you have already tested your Honda Civic's blower motor (and it's good) and need to just test the blower motor resistor (known as the blower motor power transistor), then the following tutorial will help you test it:

• Blower Motor Resistor Test (2001-2005 1.7L Honda Civic).

You can find this tutorial in Spanish here: Como Probar El Motor Soplador Del Aire Acondicionado (1.7L Honda Civic) (at: autotecnico-online.com).

How The Blower Motor Works

To understand the how and why of the tests in this tutorial, it'll help if we know how your Honda Civic's blower motor works.

In a nutshell, when you turn your Civic's ignition switch to the ON position:

1. Fuse #14 of the under-dash fuse box powers up and then feeds the number #2 terminal slot of the blower motor relay (on the under-hood fuse/relay box).
   • Fuse #14 is a 10 amp fuse.
   • Fuse #14 (of the under-dash fuse box) is the one that feeds battery power to the blower motor's coil.
   • Fuse #14 connects to relay terminal slot #2 of the under-hood fuse box.
2. Fuse #12 of the under-hood fuse/relay box is always hot.
   • Fuse #12 is a 40 amp fuse.
   • Fuse #12 (of the under-hood fuse box) is the one that feeds battery power to the blower motor (once the blower motor relay activates).
   • Fuse #12 connects to relay terminal slot #3 of the under-hood fuse box.
3. As soon as the blower motor relay's coil is fed power from the #14 fuse (of your Civic's under-dash fuse box):
   1. The blower motor relay activates (since relay terminal slot #1 is always connected to chassis Ground).
   2. The relay closes the power feed circuit to the blower motor and the BLU/WHT (blue w/ white stripe) wire of the blower motor harness connector now has battery power (from the #12 fuse of the under-hood fuse box).
      1. NOTE: In some vehicles this BLU/WHT wire is a GRN/WHT (green w/ white stripe) wire.
4. Even though the relay has now given the blower motor juice to run, it doesn't because the blower motor resistor (power transistor) has not connected the blower motor to the Ground it needs to run.
5. When you turn on the heater and select a fan speed:
   • The blower motor resistor (power transistor) now activates and lets a varying amount of Ground thru' to the blower motor.
   • This varying amount of Ground is what controls the blower motor fan speed.

Testing the blower motor and the blower motor relay isn't hard. Let's start with the first test.

TEST 1: Checking The Basics

To get your Honda Civic blower motor diagnostic on the road, in this first test we'll check 3 specifics things.

One, that the blower motor relay fuse in the under-dash fuse box is not blown.

And two, that the blower motor fuse in the under-hood is not blown.

We'll also verify that the blower motor is really getting the juice (the blower motor relay is sending) when the key is in the ON position.

These are the test steps:

1. 1

   Check that fuse #12 of the under-hood fuse box is not blown.
   
   This is a 40 amp fuse (see image 1 of 2 in the image viewer).

2. 2

   Check that fuse #14 of the under-dash fuse box is not blown.
   
   This is a 10 amp fuse (see image 2 of 2 for the location of this fuse).

3. 3

   Unplug the blower motor from its harness connector and using your multimeter, check that terminal labeled with the number 1 (image 3 of 3 in the image viewer) has battery power when the key is in the ON position (position II).
   
   NOTE: Depending on your specific Honda Civic, the wire that connects to the #1 terminal of the blower motor connector will be a BLU/WHT wire or a GRN/WHT wire.

Let's take a look at your test results:

CASE 1: Both fuses were not blown and power is present on the BLU/WHT wire. This is the correct and expected test result.

More importantly, it tells you that your Honda Civic's blower motor relay is OK and not the cause of the issue you're having with the inoperative blower motor.

Your next step is to bypass the blower motor resistor (known as the blower motor power transistor) and check the blower motor directly. For this test go to: TEST 2.

CASE 2: One (or both) fuses were blown. Replace the fuses and retest.

Now since fuses don't get blown for no particular reason, you'll need to find out why they blew in the first place since there's a good chance you've got a short in the circuits those fuses are protecting.

CASE 3: Both fuses are OK but power was NOT present. This usually indicates that the blower motor relay is bad. The blower motor relay can be tested. For this test, go to: TEST 3: Testing The Blower Motor Relay (Part 1).

TEST 2: Bypassing The Blower Motor Resistor

If you've reached this point, you have confirmed that your Honda Civic's blower motor is getting power on the BLU/WHT (or GRN/WHT) wire of its harness connector.

In this test step, we're gonna' bypass your Civic's blower motor resistor and see if the blower motor will turn on when you open the ignition switch.

The basic idea here is to add power and Ground to the blower motor without removing it from its location under the dash.

Adding power power is the easy part since it involves just opening the ignition switch. To add Ground to the blower motor, we need to bypass the blower motor resistor (known as the blower motor power transistor).

IMPORTANT: For this test to work, you must be certain that the blower motor is getting power when you turn the key to the ON position (position II) on the BLU/WHT wire (or GRN/WHT wire depending on your specific Honda Civic) of the blower motor's 2 terminal connector.

1. 1

   Unplug the blower motor resistor (known as the blower motor power transistor).

2. 2

   Using a jumper wire, jumper terminals 4 and 2 of the blower motor resistor's harness connector (see photo in the image viewer).
   
   Terminal #2 is has the BLK wire attached to it and this wire connects directly to chassis Ground. Terminal #1 has the BLU/WHT (or GRN/WHT) wire connected to it.

3. 3

   Turn the key to the ON position (position II) to power up the circuit.

4. 4

   You should see one of two results: the blower motor will come on or it won't.

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

CASE 1: The blower motor came on when you turned the key to the ON position. This test result tells you that the blower motor is OK and that the reason it's not coming on is due to a possible problem with the blower motor resistor (known as the power transistor).

Thankfully, you can test your Honda Civic's blower motor resistor and thus be absolutely sure that it's fried and behind the cause of the ‘no blower’ condition. The following step-by-step tutorial will show you how to test the blower motor resistor (power transistor):

1. Blower Motor Resistor Test (2001-2005 1.7L Honda Civic).

CASE 2: The blower motor DID NOT come on when you turned the key to the ON position. This test result tells you that the blower motor is fried and needs to be replaced.

Here's why: So, far, you have:

1. You have checked the 2 fuses that feed the blower motor relay and the blower motor (TEST 1).
2. You have verified that terminal number 1 of the blower motor connector is hot when the ignition switch is in the ON position (TEST 1).
3. You have bypassed the blower motor resistor in this test.

So, taking all of the above into account, the blower motor should have turned on when you opened up the ignition switch. Since it did not, you can correctly conclude that the blower motor is bad and needs to be replaced.