How To Test The PWM Fan Relay (1997-1999 2.0L Dodge/Plymouth Neon)

TEST 5: Manually Activating The PWM Fan Relay (Fan Motors Disconnected)

In this test section, we're gonna test the PWM fan relay performance with the radiator fan motor or motors disconnected from their electrical connectors.

Why should you test the PWM fan relay with the radiator fan motors disconnected from their electrical connectors? Here are the key reasons:

• Uncertainty About Amperage Draw: If you're not sure whether the total amperage draw of the fan motor(s) is under 30 Amps, it's safer to test the relay without the fan motors connected. This way you avoid the risk of damaging the PWM fan relay.
• High Amperage Draw: If you've already confirmed that the amperage draw of the fan motor(s) is 30 Amps or more, testing the PWM fan relay with the fan motors unplugged is essential. This way, you can determine if the relay is functioning properly or if it needs to be replaced along with the bad fan motor(s).
• Results from TEST 4: If you've completed TEST 4 and the fan motor(s) did not run, the next step is to check whether the voltage output from the relay is actually reaching the fan motor(s). This test will help help further pinpoint the cause of the issue.

OK, let's get into the specifics. In this test we're about to perform, we'll manually activate the PWM fan relay. This will supply 10 to 12 Volts to the fan motor(s) through the relay connector's light green (LT GRN) wire.

To confirm that the voltage has indeed reached the fan motor(s), we'll use a multimeter set to Volts DC mode and check for the presence of the 10 to 12 Volts at the LT GRN wire of the radiator’s 2-wire connector.

Testing the PWM fan relay in this manner enables us to verify whether the relay is working correctly. It also eliminates the risk of frying the relay during the test, which could happen if the fan motors were connected to the electrical circuit and they're faulty.

These are the test steps:

1. 1

   Disconnect the following components from their electrical connectors:
   
   A.) The negative (-) battery terminal from the battery.
   
   B.) The PCM from its connector(s).
   
   C.) The radiator fan motor or fan motors from their electrical connectors.

2. 2

   Attach a wire piercing probe to the dark green wire (DK GRN) of the PWM fan relay connector.
   
   NOTE: The PWM fan relay must remain connected to its 4-wire connector during the test.

3. 3

   Reconnect the negative (-) battery cable to the battery.
   
   NOTE: The PCM connector(s) must remain disconnected from the PCM.

4. 4

   Place your multimeter in Volts DC mode.

5. 5

   Connect the black multimeter test lead to the battery negative (-) terminal.
   
   Leave the black multimeter test lead connected to the battery negative (-) terminal.

6. 6

   Connect one end of a jumper wire to the wire piercing probe that is connected to the DK GRN wire.

7. 7

   Connect the other end of the jumper wire to the battery negative (-) terminal.
   
   This will trigger the activation of the PWM fan relay.
   
   NOTE: Since the fan motor or motors are disconnected, it's safe to leave this end of the jumper wire connected to the battery negative (-) terminal.

8. 8

   With the red multimeter test lead, probe the female terminal of the radiator fan motor connector that connects to the light green (LT GRN) wire.
   
   This is the engine wiring harness connector and it should have a LT GRN wire and a BLK wire.

9. 9

   Your multimeter should report 10 to 12 Volts if the PWM fan relay is OK.

Let's interpret your test result:

CASE 1: The indicated voltage is present in the LT GRN wire when the relay was activated. This is the correct and expected test result and it tells you that the PWM fan relay and the LT GRN wire is OK and functioning correctly.

CASE 2: The indicated voltage WAS NOT present in the LT GRN wire when the relay was activated. You can conclude that the PWM fan relay is bad and needs to be replaced if you have:

• Confirmed that terminal 4 has 10 to 12 Volts DC (TEST 2).
• Confirmed that terminal 1 has Ground (TEST 3).
• In this test section, confirmed that manually activating the relay, the LT GRN wire does not have 10 to 12 Volts present at the engine wiring harness connector that connects to the fan motor(s).

If you still haven't checked the amperage draw of the fan motor(s). Do so before installing a new PWM fan relay. Remember, the number 1 killer of PWM fan relays is a fan motor or motors consuming 30 Amps or more when running.

You can find the test here:

• How To Test The Radiator Fan Motor (1997-1999 2.0L Dodge/Plymouth Neon)