Radiator Fan Motor Switch Diagnostic Tests (1995-2000 1.6L Honda Civic)

By: Abraham Torres-Arredondo
Created: 24 November 2024
Updated: 28 November 2024
Articl Id: 1382

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TEST 3: Jumpering The Coolant Temp Switch Connector

Jumpering The Coolant Temp Switch Connector. How To Test The Coolant Temperature Switch (1995, 1996, 1997, 1998, 1999, 2000 1.6L Honda Civic)

In this test section, we're going to disconnect the radiator fan switch and use a jumper wire to connect its two terminals.

If there are no issues in the radiator fan motor circuit, the radiator fan motor will turn on. If the fan motor activates, we can confirm several key things:

The radiator fan relay is working properly.
The radiator fan motor is in good condition.
The two fuses supplying power to the radiator fan relay are intact.
There are no electrical problems in the radiator fan motor system's wiring.

If the fan motor doesn't activate, we'll move on to TEST 3 to check if the radiator fan relay is receiving power.

CAUTION: Only perform this test when the engine is cold. Trying to disconnect the coolant temperature switch from its connector on a hot engine can lead to burns.

Let's get started:

1
Disconnect the coolant temp switch.
2
Jumper the two female terminals with a jumper wire.

You can use a paper-clip as the jumper wire.

IMPORTANT: Make sure the ends of the jumper wire you're inserting into the connector terminals are thin enough to avoid damaging the female terminals. Using a thicker wire can damage to the connector and if this happens, you'll need to replace it.
3
Turn the key to the ON position but don't crank or start the engine.
4
You'll get one of two results.

1.) The radiator fan motor will run.

2.) The radiator fan motor will not run.

Let's take a look at your test results:

CASE 1: The radiator fan motor ran. This is the correct test result. You can conclude that all of the components that make up the radiator fan motor system circuit are OK.

With this test result, you can conclude that the coolant temperature switch is bad and needs to be replaced if you have:

Confirmed that the amperage draw of the radiator fan motor is under 15 Amps (1995 1.6L Honda Civic) or 20 Amps (1996-2000 1.5L Honda Civic).
Confirmed the radiator fan relay fuse and the radiator fan motor fuse are not blown (TEST 1).
Confirmed that the fan motor does not run when the coolant temperature reaches between 195°F-225°F (TEST 2).
Confirmed, in this test step, that the radiator fan motor runs when jumpering the terminals of the coolant temperature switch.

CASE 2: The radiator fan motor DID NOT run. This could be the result of a bad radiator fan relay.

The next step is to swap the radiator fan relay with a neighboring relay (and in this way, indirectly check to see if its bad). For this test, go to: TEST 4: Swapping The Radiator Fan Relay.

TEST 4: Swapping The Radiator Fan Relay

Swapping The Radiator Fan Relay. How To Test The Coolant Temperature Switch (1995, 1996, 1997, 1998, 1999, 2000 1.6L Honda Civic)

So far, you've confirmed:

The amperage draw of the radiator fan motor is under 15 Amps (1995 1.6L Civic) or under 20 Amps (1996-2000 1.6L Civic).
The radiator fan relay fuse and the radiator fan motor fuse are not blown (TEST 1).
The fan motor does not run when the coolant temperature reaches between 195°F-225°F (TEST 2).
The radiator fan motor does not run when the terminals of the coolant temp switch connector are jumpered (TEST 3).

In this test section, we're going to swap the radiator fan relay with a neighboring relay in the under-hood fuse/relay box.

Once you've placed the other relay into the radiator fan relay slot, we'll jumper the terminals of the coolant temp switch connector again.

If the original relay is bad, the new relay should activate and cause the radiator fan motor to run.

Rad Fan Relay Location: You can find the location of the radiator fan relay here:

Radiator Fan Relay Bench-Test: The following tutorial will help bench-test the radiator fan relay:

How To Bench-Test The Radiator Fan Relay (1996-2000 1.6L Honda Civic).

These are the test steps:

1
Remove the radiator fan relay.
2
Replace the radiator fan relay with a neighboring relay from the same fuse/relay box.

NOTE: Make sure the replacement relay is seated securely in the radiator fan relay slot.
3
Jumper the coolant temp switch connector.
4
Turn the key ON but don't crank or start the engine.
5
The radiator fan motor should run.

Let's interpret your test result:

CASE 1: The radiator fan motor turned ON. This is the correct and expected test result.

This test result tells you that the original relay is bad and needs to be replaced, if you have:

Confirmed that the radiator fan motor system fuses are not blown (TEST 1).
Confirmed that the radiator fan motor does not run at the specified coolant temp range (TEST 2).
Confirmed that the radiator fan does not turn on when jumpering the coolant temp switch connector with the original relay installed (TEST 3).
Confirmed that the radiator fan does run after swapping the relay (this test section).

CASE 2: The radiator fan motor DID NOT turn ON. This result usually indicates there's an electrical "open-circuit" problem somewhere in the radiator fan motor circuit wiring.

While troubleshooting this is beyond the scope of this tutorial, your next steps should include:

Checking the continuity of the wiring between the coolant temp switch connector and the relay slot.
Checking the continuity of the wiring between the relay slot and the radiator fan motor connector.
Verifying that the radiator fan motor has a proper path to Chassis Ground.

The following diagrams will come in handy:

More 1.6L Civic Tutorials

You can find a complete list of 1.6L Honda Civic tutorials in this index:

1.6L Honda Civic Index Of Articles.

Here's a small sample of the 1.6L Honda Civic tutorials you'll find in the index:

If this info saved the day, buy me a beer!