In this tutorial, I'll show you how to bench-test the radiator fan relay step-by-step.
This is a pretty simple test that's done with a multimeter and jumper wires. With your test results, you'll easily and quickly find out if the relay is good or bad.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 1.6L Honda Civic CX: 1996, 1997, 1998, 1999, 2000.
- 1.6L Honda Civic DX: 1996, 1997, 1998, 1999, 2000.
- 1.6L Honda Civic EX: 1996, 1997, 1998, 1999, 2000.
- 1.6L Honda Civic LX: 1996, 1997, 1998, 1999, 2000.
What Tools Do I Need To Test The Relay?
The cool thing about testing the relay is that you don't need any expensive tools. Here's what you'll need:
- Multimeter:
- The multimeter can be digital or analog multimeter.
- If you need to buy one or are looking to upgrade, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
- Jumper Wires:
- You'll need two of them with alligator clips on both ends (you can make these yourself).
Radiator Fan Relay Basics
The radiator fan relay on the 1996–2000 1.6L Honda Civic has 4 male spade terminals, and it's made up of two circuits:
- The coil circuit (also called the control circuit). Terminals 3 and 4 connect to this circuit.
- The load circuit (or power circuit). Terminals 1 and 2 connect to the load circuit.
The coil circuit is the low-current side of the relay. When it gets power, it energizes the relay, closing the load circuit.
The load circuit is the high-current side, which when 'closed' by the coil circuit, sends current to the radiator fan motor.
In the illustration above, I've labeled the relay male spade terminals 1 through 4 to make things easier to follow:
- Terminal 1 gets power from Fuse 57 (1996–2000 Civic) in the under-hood fuse/relay box.
- Terminal 2 connects to the radiator fan motor.
- Terminal 3 gets power from Fuse 17 (1996–2000 Civic) in the under-dash fuse/relay box.
- Terminal 4 connects to the coolant temperature switch (also called the radiator fan switch).
This setup ensures the relay only sends power to the radiator fan motor when the coolant temperature switch signals it's needed.
Radiator Fan Relay Bench Test
Alright, this is what you signed up for! We'll be using the battery in your Honda Civic to bench-test the relay.
The illustration above will help you connect the jumper wires and the multimeter to the correct male spade terminals of the relay.
Let's get testing:
- 1
Set your multimeter to Ohms mode.
- 2
Connect terminal 3 to the battery positive (+) terminal with a jumper wire.
- 3
Connect terminal 4 to the battery negative (-) terminal with a jumper wire.
You should hear a click when connecting the relay to battery negative (-) terminal. - 4
Connect the red multimeter test lead to terminal 1.
- 5
Connect the black multimeter test lead to terminal 2.
- 6
Your multimeter should read continuity (less than 1 Ohm).
- 7
Remove the jumper wire from terminal 4.
This will deactivate the relay. - 8
Your multimeter should read NO continuity (OL - over limit).
Let's interpret your test result:
CASE 1: Terminals 1 and 2 have continuity when powering terminals 3 and 4. This is the correct and expected test result.
This result tells you that the relay is good and functioning correctly.
CASE 2: Terminals 1 and 2 HAVE NO continuity when powering terminals 3 and 4. This tells you that the relay is bad and needs to be replaced.
More 1.6L Civic Tutorials
You can find a complete list of 1.6L Honda Civic tutorials in this index:
Here's a small sample of the 1.6L Honda Civic tutorials you'll find in the index:
- Testing Shift Control Solenoid Valves A and B (1996-2000 1.6L Honda Civic).
- How To Test The Alternator (1996-2000 1.6L Honda Civic).
- How To Test: Lock-up Control Solenoid Valves (1996-2000 1.6L Honda Civic).
- How To Test Trouble Code P0135 (1995-2000 Honda 1.6L).
- How To Test The Igniter, Ignition Coil Accord, Civic, CRV, and Odyssey (at:easyautodiagnostics.com).
If this info saved the day, buy me a beer!
