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Has two radiator cooling fans but none is working while the engine is running

Tiny
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  • MEMBER
  • 2003 TOYOTA RAV4
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 196,457 MILES
Hello, I am working on a vehicle, it has two radiator cooling fans but none is working while the engine is running. The two fans only operate when the air-conditioning is engaged. I thought it is the thermostat initially, I started the engine and allowed it to run for some times, the engine almost overheat but the fans could not run. What could be the cause and how can it be fixed?
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Wednesday, September 23rd, 2020 AT 12:37 PM

24 Replies

Tiny
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Good afternoon,

The first thing I would do is remove the coolant sensor connector and with the key on, see if the radiator fans come on.

If they do not, try jumping the 2 wires together and recheck.

I attached a wiring diagram for the system for you.

Let me know when you want to do some voltage testing.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Roy
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Wednesday, September 23rd, 2020 AT 1:59 PM
Tiny
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Good morning, disconnecting the connector from the sensor or jumping the wires together, if the fans picked up, does it mean that the sensor is faulty or what?
What if the fans does not picked up, what is the next step to take?
The owner of the vehicle is currently using his vehicle, so I want to tell him exactly what is wrong with his vehicle whenever I call him.
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Friday, September 25th, 2020 AT 12:42 AM
Tiny
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If the fans come on then yes, the sensor is the issue.

If they do not then we will need to do some electrical testing to determine the failure. At this point it is too early to be able to say the issue until diagnostics are done.

Roy
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Friday, September 25th, 2020 AT 2:02 AM
Tiny
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Good morning,

From the circuit diagram you sent. Is there any difference between the engine coolant temperature sensor and the engine coolant temperature switch?
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Sunday, September 27th, 2020 AT 2:42 AM
Tiny
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Yes, the sensor is measuring the temperature of the coolant in the engine.

The switch is measuring the temperature at the radiator itself.

I attached a picture of the location for you to view.

Roy
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Sunday, September 27th, 2020 AT 4:21 AM
Tiny
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Thank you, but is it all vehicles that have it or just Toyota? I mean the coolant temperature switch.
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Sunday, September 27th, 2020 AT 6:14 AM
Tiny
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Depends on the manufacturer. There are several that incorporate this.

Roy
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Sunday, September 27th, 2020 AT 6:15 AM
Tiny
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Good evening, I have removed the connector from the sensor, the fans didn't function and I jumped the two wires together yet it didn't work. I tested for voltage at the connector terminals it was 5 volts.
What is next step?
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Sunday, September 27th, 2020 AT 11:30 AM
Tiny
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Which sensor? The one on the engine or the one in front of the car?

Roy
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Sunday, September 27th, 2020 AT 11:46 AM
Tiny
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Hello, the one on the engine.
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Sunday, September 27th, 2020 AT 6:54 PM
Tiny
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Go to the one under the hood and jump the 2 terminals and see if the fans come on.

Roy
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Monday, September 28th, 2020 AT 1:38 AM
Tiny
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That's what I have already done in my previous post. It didn't come on.
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Monday, September 28th, 2020 AT 6:25 PM
Tiny
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Go to the one behind the grille and see if it comes on.

That one will stop the fans from coming on if it is not closing.

Roy
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Tuesday, September 29th, 2020 AT 1:07 AM
Tiny
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You mean the switch, how does it looks like?
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Tuesday, September 29th, 2020 AT 6:50 PM
Tiny
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Hi,

The coolant temperature switch is located at the bottom of the radiator. See the attached pic. I believe that is the one that Roy is referring to.

Let us know if you find it.

Joe
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Wednesday, September 30th, 2020 AT 7:04 PM
Tiny
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Thank you.
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Wednesday, September 30th, 2020 AT 7:51 PM
Tiny
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Let us know if connecting the 2 wires together makes the fan come on.

You are welcome.

Roy
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Thursday, October 1st, 2020 AT 1:22 AM
Tiny
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Good morning, the fans are now functioning without AC engaged.
The engine coolant temperature switch was disconnected before now. Jumping the wires together with the engine running, the fans picked up.
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Monday, October 12th, 2020 AT 5:09 PM
Tiny
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Okay, that indicates the coolant switch is bad, replace that switch.

Roy
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Monday, October 12th, 2020 AT 5:11 PM
Tiny
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Since, the engine coolant switch, A/C single pressure switch and the engine coolant temperature sensor (from the circuit diagram) can complete the circuit for both fans to function. What is the function of fan relay 2?
Where is engine coolant temperature sensor grounded?
At what condition will the A/C condenser fan motor and radiator Fan motor connected in series (from the circuit diagram)?
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Monday, October 12th, 2020 AT 5:23 PM

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