Hi there
I have a 3litre V6 Toyota harrier that I bought while Im working in Malawi for a year. Its in fairly good shape but the cooling fans don't switch on.

• When you switch on the air con the fans both come on in low speed mode.
• When you disconnect the temp sensor the fans both come on in high speed mode.
• The temperature gauge does not read very high but in this hot climate I wonder whether its not reading correctly.
• when hot the temp sensor measures about 480 ohms

Any ideas or suggestions would be appreciated.
Thanks
Ken

 

RX engine runs hotter than other engines. But all temperature related information is based on coolant temperature and it is imperative that there is enough coolant.

With engine cold, open the radiator cap to ensure there is enough coolant.

If you don't mind, please educate us regarding the climate of your location.

Salim

 

Hi Salim and thanks for your prompt reply
Its currently 24-26 degree C but it goes well into the 30s in October /November. It has a hot humid tropical climate.

Would I be correct in assuming that the relays are not at fault- I can get both fans to run at high speed by disconnecting the temp sensor.
Is there a way I could test the fan computer that sits on the top of the radiator?
Are there other temp sensors that could be faulty? I cannot see a sensor on the radiator.
Thanks
Kenneth

 

Can you clarify what "the cooling fans don't switch on" means? Is the car overheating?

 

Hi Thanks maxSteel
The temp gauge says its not overheating but the engine does feel very hot. I would expect the cooling fans to kick in when stationary. The fans have never switched on once since we got the car about six weeks ago.
Regards
Kenneth

 

Please confirm, I am going to state what my understanding is ...
There is a temperature gauge [near the thermostat] and a thermal switch at the bottom of the radiator. The thermal switch provides a path to Ground to kick the fan on. The thermal gauge provides the signal to ECU and the engine temp gauge.

If your coolant level iOS good and the temp gauge shows close to 50%, I would not worry.

If you want to confirm, please get hold of the wiring diagram. Once you confirm that the thermal switch does provide a path to ground, you can by pass it to confirm that the fan does come on.

Salim

 

Thanks Salimshah
You are correct that there is a two wire temp sensor to the rear of the top hose. I cannot see a bottom radiator sensor- after a good look around I have found a sensor in front of the aircon radiator but it looks like an air temp sensor- I will try and attach photos.
The coolant level is good.

Temp sensor behind top hose

sensor in front of radiator and aircon matrix

 

That last one is probably the ambient temperature sensor

 

After I drove my car a while and then idled for about 10-15 minutes, A/C off, I checked under the hood. Fans are off. When I turn A/C on, fans turn on.
Ambient temperature almost 80F.

I would agree with Salim. If coolant level is right and temperature gauge is reporting correctly you probably have no issue.

 

Thanks Salimshah and MaxSteel for your thoughtful and prompt responses. Very Helpful

 

As a final non-invasive check, you can check if both fans are running when AC is on after you have driven on a hot day.

Salim

 

hello again.
It's now over 30degrees C here in southern Malawi and the Lexus (Toyota Harrier 3.0) is still running fine and the temp gauge is sitting at normal.
my concern is that the fans still don’t run until you disconnect the temp sensor.
We are planning a drive across Zambia, Zimbabwe and Namibia in December and don’t want overheating problems in remote areas.

should I just stop worrying because the temp gauge is at normal?
thanks
Kenneth

 

To maximize efficiency, every ounce of energy is conserved while trying to maintain optimum operating temperature. The thermostat opens and closes to bring in cooler coolant from the radiator. Once the radiator fails to cool any further, the fan motor is engaged to force cooling of the radiator. If the vehicle is moving, the air is forced over the radiator, reducing the need to turn on the fan. You can choose to override and run the fan all the time, it is your choice. I would tend to say everything is working fine, unless your temp gauge starts to move away from [both high and low] optimum position.

Salim

 

Can I add, I use a scanner to monitor the coolant temperature and make sure my fans turn on perfectly when they should.

Here is the test for the switch.
For cooling fan temps plz see next post.





For trips I never leave home without a proper scanner, a jug of coolant with rags and funnel, extra tools, spare coils, etc.

 

Hi friends, I updated the last post, that was for the switch not the cooling fan temps so I had to do a live test because I starting doubting myself from the last test I did..

Did a live test on my RX330 today and here is what I came up with for actual fan on & off temps using my scanner and watching the fans.
I'm sorry I don't have an RX300 to compare so this is the best I can do so hopefully someone can compare.


Test Conditions: Car is running, A/C is off
Driver side fans turn on at exactly 204F as I watched





Driver side fan turns off at 201F



This cycle repeats over and over and over and over.