Question on Radiator/AC Condenser fan speed

[rayfloyd170]

Hi,

I'm just curious and wanted to know if this is normal behavior of the Cooling Fan for radiator/AC Condenser of Yaris Gen 3.

The LOW SPEED of the Fan comes ON only when i switch on my A/C while engine is still cold. If the A/C is OFF it wont spin at low speed however when it reaches 96degC it automatically spins at high speed which is expected to cool the engine. High speed fan stops cyclic at about 88-90degC and comes On again when it reaches 96degC but the low speed never turns ON when A/C is OFF.

I am expecting the Low Speed to always turn ON but it does not especially when A/C is OFF. I am not sure if this is how it really works.

I already checked the Fan relay No.1(4pins) and Fan relay No.2 (5pins) and the 1.3ohm resistor. All of them are good and working fine.

Although i am still safe from overheating since the high speed works even if the A/C if OFF, i just dont like the engine always reaching 96deg cyclically. Th low speed fan should always be working in my understanding regardless of A/C is OFF or ON.

Your ideas are highly appreciated.

[kevinj93]

Hi,

According to the service manual description, the ECM turns on or off the cooling fan relays based o engine coolant temperature, air conditioning switch, refrigerant pressure, engine speed and vehicle speed signals.

Fan relay number 1 turns the fan on or off. Fan relay number 2 switches between high and low speed when the fan is on.

I can't find a reference to the actual coolant temperatures that trigger high or low speed fan operation, but the thermostat does not begin to open until the coolant temperature is 80 to 84 degrees celsius, should fully open at 95 degrees celsius, and should be fully closed at 77 degrees celsius.

Unfortunately, I can't find a specification for temperatures where the fan is expected to turn on or off, or change between low and high speed.

[rayfloyd170]

Originally Posted by kevinj93

Hi,

According to the service manual description, the ECM turns on or off the cooling fan relays based o engine coolant temperature, air conditioning switch, refrigerant pressure, engine speed and vehicle speed signals.

Fan relay number 1 turns the fan on or off. Fan relay number 2 switches between high and low speed when the fan is on.

I can't find a reference to the actual coolant temperatures that trigger high or low speed fan operation, but the thermostat does not begin to open until the coolant temperature is 80 to 84 degrees celsius, should fully open at 95 degrees celsius, and should be fully closed at 77 degrees celsius.

Unfortunately, I can't find a specification for temperatures where the fan is expected to turn on or off, or change between low and high speed.

Thank you so much for this very clear information.

I thought my cooling fan is behaving weird but now i come to know it is just normal due to a lot of variables as you mentioned above.

This should be due to the ECM turning on or off the cooling fan relays depending on the parameters.

[kevinj93]

Glad you found the information useful.