TEST 2: Testing The Amperage Draw Of The High Speed Radiator Fan Motor
Now that you have tested the amperage draw of the low speed circuit, we're now gonna' test the amperage draw of the high speed circuit of the radiator fan assembly.
This test follows the same testing procedure as that of TEST 1. The difference is that we'll be testing the male terminal labeled with the number 4 in the photo above.
If the amperage draw is over 40 Amps or if your digital multimeter shows an over the limit (OL) value, then you can conclude that the fan motor assembly is bad and needs to be replaced.
NOTE: This test is done on the 4-wire connector with male spade terminals
These are the test steps:
- 1
Disconnect the 4-wire radiator assembly connector.
- 2
Place your multimeter in Ohms mode.
- 3
Connect the black multimeter test lead to the battery negative (-) access point (located on the driver side strut tower).
- 4
Probe the male terminal labeled with the number 4 with the red multimeter test lead.
- 5
Write down the resistance value your multimeter registers.
- 6
Divide 12.5 by the resistance value (12.5 is the battery voltage).
The calcution should look like this 12.5 ÷ your resistance value = amperage draw - 7
The result of this calculation is the amount of amperage the fan motor is using.
To be a bit more specific: Let's say that the resistance reading was 0.4 Ohms. This is what the math would look like: 12.5 ÷ 0.4 = 31.25 and this would translate to 31.25 Amps.
Let's analyze your test result:
CASE 1: The amperage draw is under 40 Amps. This is the correct and expected test result.
The next step is to make sure that both radiator fan motor relays are getting power. For this test go to: TEST 3: Making Sure Both Fan Motor Relays Are Getting 12 Volts.
CASE 2: The amperage draw is over 40 Amps. This lets you know that the high speed radiator fan motor has failed due to excessive wear and tear. Replace the radiator fan assembly.
TEST 3: Making Sure Both Fan Motor Relays Are Getting 12 Volts
The low speed and high speed relays get power from the same 2 fuses (see image 2 of 3). These fuses are:
- Fuse 12 (40 A) of the Power Distribution Center.
- Fuse 23 (20 A) of the Power Distribution Center.
Before we continue with our radiator fan motor diagnostic we need to make sure that these 2 fuses are providing 10 to 12 Volts to the fan motor relays.
What we'll do is test for the presence of 10 to 12 Volts on female terminals number 71 and number 74 of the low speed radiator fan relay socket. This socket is on the Power Distribution Center (see image 3 of 3 above).
If 10 to 12 Volts DC are present at female terminals 71 and 74, then we can conclude that the fuses are OK and we can also conclude that female terminals 76 and 79 (of the high speed radiator fan relay) are also receiving this voltage.
NOTE: Be careful when probing the female terminals of the relay socket with your multimeter test lead.
These are the test steps:
- 1
Remove the low speed radiator fan motor relay from the Power Distribution Center.
- 2
Turn the key ON but don't start the engine.
- 3
Locate female terminals 71 and 74 of the relay socket (see illustration 3 of 3).
- 4
Gently probe female terminal number 71 with the red multimeter test lead.
- 5
Ground the black multimeter test lead on the battery negative (-) access point (on the left-side strut tower).
- 6
Your multimeter should read 10 to 12 Volts DC.
- 7
Repeat steps 3 through 5 on female terminal 74.
Female terminal 74 should also have 10 to 12 Volts present with the key ON.
Let's analyze your test result:
CASE 1: Both female terminals (71 and 74) have 10 to 12 Volts. This is the correct and expected test result.
You can conclude that fuse 12 and fuse 23, of the Power Distribution Center, are OK (not blown). You can also conclude that female terminals 76 and 79 of the high speed radiator fan relay are also receiving these 10 to 12 Volts DC.
The next step is to apply battery power to the low speed circuit of the radiator fan motors. Your next step is to go to: TEST 4: Bypassing The Low Speed Fan Motor Relay.
CASE 2: Female terminal 71 DOES NOT have 10 to 12 Volts. This is very rare but a lack of 10 to 12 Volts at female terminal 71 generally lets you know that fuse 23 of the Power Distribution Center is blown.
Your next step is to check the fuse and if it's blown, replace it with a new one (of the same rating). After replacing the fuse check that terminal 71 has 10 to 12 Volts.
CASE 3: Female terminal 74 DOES NOT have 10 to 12 Volts. This test result generally lets you know that fuse 12 of the Power Distribution Center is blown.
This is usually caused by a bad radiator fan motor or fan motors drawing more than 40 Amps as they run.
Your next step is to check the fuse and if it's blown, replace it with a new one (of the same rating). After replacing the fuse check that terminal 74 has 10 to 12 Volts.
If you haven't already tested the amperage draw of the fan motors, then that is your next step go to: TEST 1: Testing The Amperage Draw Of The Low Speed Radiator Fan Motor.
If you have tested the amperage draw of the low and high speed circuits of the fan motors, then your next step is: TEST 4: Bypassing The Low Speed Fan Motor Relay.
TEST 4: Bypassing The Low Speed Fan Motor Relay
In this test step, we're gonna' apply battery power to the low speed circuit of the radiator fan motors by bypassing the low speed radiator fan relay with a jumper wire.
To be a little more specific: We're gonna' jumper terminal number 72 and terminal number 74 of the relay socket in the Power Distribution Center (under-hood fuse box).
Illustration 1 of 2 shows the location of the low speed radiator fan motor and illustration 2 of 2 will help you identify the female terminals we need to jumper together.
The correct and expected test result is for the fan motors to run in low speed when both terminals are jumpered together.
IMPORTANT: Do not jumper any other terminals of the relay socket than the ones indicated! Jumpering any other female terminals can damage the fuel injection computer.
These are the test steps:
- 1
Remove the low speed radiator fan motor relay from the Power Distribution Center.
- 2
Locate female terminals #72 and #74 of the relay socket (see illustration 2 of 2).
- 3
Connect one end of the jumper wire to the terminal labeled with the number 72 (see illustration 2 of 2).
- 4
Connect the other end of the jumper to the terminal labeled with the number 74 (see illustration 2 of 2).
- 5
The both fan motors should run in low speed.
Let's analyze your test result:
CASE 1: Both fan motors ran. This is the correct and expected test result.
You can conclude that the low speed circuit of both fan motors is OK if you have confirmed that their amperage draw is less than 40 Amps in TEST 1.
The next step is to apply battery power to the high speed circuit of the radiator fan motors. Your next step is to go to: TEST 5: Bypassing The High Speed Fan Motor Relay.
CASE 2: Both fan motors DID NOT run. This test result generally lets you know that the fan motors are bad and that the radiator fan assembly needs to be replaced.
But to be sure they're bad, you need to make sure that the fan motors are getting power and Ground. Your next step is to go to: TEST 6: Making Sure The Radiator Fan Assembly Is Getting Power From The Low Speed Relay.
CASE 3: One fan motor ran but NOT both. The fan motor that did not run is bad. Replace the radiator fan assembly.
