The blower motor relay on the 2001-2005 1.7L Honda Civic is an electro-mechanical relay that can be easily be bench tested to find out if it's bad (or good).
In this tutorial I'll show you how to do it since all that's required to bench test it is to apply power and Ground to the blower motor relay's coil and then test for continuity on the controlled circuit's metal terminals (don't worry, it's not as hard as it sounds).
This tutorial complements the following tutorials:
- How To Test The Blower Motor (2001-2005 1.7L Honda Civic).
- How To Test The Blower Motor Power Transistor (2001-2007 Honda Civic).
You can find this tutorial in Spanish here: Verificando El Relé Del Motor Del Soplador (1.7L Honda Civic) (at: autotecnico-online.com).
Blower Motor Relay Bench Test
As you're probably already I aware, the relay is made up of two separate circuits. The first circuit is the control circuit.
The control circuit, when activated by battery power and Ground, controls the controlled circuit by causing it to ‘close’ (from its normally ‘open’ state). The controlled circuit is the one that connects the blower motor do battery power (relay terminals labeled with the #s 1 and 2 -see image 3 of 3).
To bench test the blower motor relay, you and I can manually add battery power and Ground to the control circuit of the relay (relay terminals labeled with the #s 1 and 2 -see image 3 of 3).
As stated before, this causes the controlled circuit to close (if the blower motor relay is good). We can confirm that this actually happened by using a multimeter (in Ohms Ω mode) to measure continuity between terminal #3 and #4 (of the now closed controlled circuit).
These are the test steps:
- 1
Remove the blower motor relay and connect male spade terminal #2 to battery Ground, using a jumper wire.
Your connections should look like the connections in photo 1 of 3 in the image viewer.
NOTE: Image 2 of 3 will show you the location of the blower motor relay in the under-hood fuse/relay box. - 2
Connect male spade terminal #1 to the battery's positive (+) terminal. This will energize and activate the relay's coil (this is the control circuit). This can be confirmed by the audible click the blower motor relay will make.
- 3
Measure the resistance across the relay's terminals #3 and #4 with your multimeter in Ohms Ω mode (as seen in the photo).
- 4
Your multimeter should show continuity. If it doesn't show continuity, recheck all your connections and retest.
- 5
Remove and reconnect the jumper wire to terminal #1 several times, as you eye-ball the multimeter.
When the jumper wire IS NOT connected to power, the multimeter should show NO CONTINUITY as indicated by the letters OL (open loop).
When the jumper wire is connected to power, the multimeter should show continuity.
Let's take a look at what your test results mean:
CASE 1: Your multimeter showed continuity. This test result tells you that the blower motor fan relay is good and is not the cause of the ‘no blower motor’ condition your Honda Civic is currently experiencing.
To continue diagnosing your Honda Civic's ‘no blower motor’ condition I recommend the following tutorials:
- How To Test The Blower Motor (2001-2005 1.7L Honda Civic).
- How To Test The Blower Motor Power Transistor (2001-2007 Honda Civic).
CASE 2: Your multimeter DID NOT show continuity. Recheck all of your test connections and retest. If your multimeter still doesn't show continuity, then the blower motor fan relay is fried and needs to be replaced.
Where To Buy The Blower Motor Relay And Save
The links below are to help you comparison shop for the blower motor relay (and related blower motor parts) online. I used to buy everything at my local auto parts store... till I found out just how they over-price everything. Below are the links to the blower motor relay, blower motor, and the blower motor resistor (also known as the blower motor power transistor).
NOTE: Not sure if the above components fit your particular Honda Civic? Don't worry, they'll make sure the part fits once you get to the web site.
More 1.7L Honda Civic Tutorials
You can find a complete list of tutorials for you Honda 1.7L equipped car here: 1.7L Honda Civic Index Of Articles.
Here's a small sample of the tutorials you'll find in the index:
- How To Test The Crank Sensor (2001-2005 1.7L Honda Civic).
- Maintenance Required Light Reset (2001-05 1.7L Honda Civic).
- How To Do A Cylinder Balance Test (2001-2005 1.7L Honda).
- How To Test Trouble Code P0141 (2001-2005 Honda 1.7L).
- How To Test The TP Sensor (2001-2005 1.7L Honda Civic).
- How To Test Trouble Code P0135 (2001-2003 Honda 1.7L).
If this info saved the day, buy me a beer!
