Understanding Fan Aux switch setpoint

[maxiz1]

Hi All,
I just wanted to understand why the 4-pin aux switch located at the lower radiator hose setpoint is "considered" high i.e. 95C to start the fan at lower speed. Nowadays, the off setpoint is 90C but I think previously it was 84C.

I can't understand why Audi allows the radiator outlet to go as high as 95C to supply the cooling liquid to the thermostat. Wouldn't the engine end up much higher temperature then?

I noticed that older model has a different 3-pin aux switch set somewhat around 84C located just above the lower radiator outlet joint. This for me make more sense since you want to always have a much cooler fluid readily available for the thermostat to utilize.

Please help me understand this rational. Thanks.

[RMode]

because it's an aux fan, not the main fan. The thermostat opens at 87C, so not quite sure what you're trying to say by "why Audi allows the radiator outlet to go as high as 95C to supply the cooling liquid to the thermostat."

A properly working coolant system can sit in traffic, not moving, for hours and hours on end, and maintain stable coolant temp

[walky_talky20]

I think the main factor would be noise complaints from owners. Constantly kicking in the fan in and out due to a setpoint that is slightly lower may have customers thinking their car is "extremely loud" with a "fan that runs constantly" and that obviously "can't be right because car X I had before didn't do this". The dual speed e-fan is able to rapidly cool the system, so letting is spike a little higher isn't a big deal.

Another factor may be their foray into "mapped cooling systems" on other cars starting around this time (2000+). On the B6 A4, for example, the thermostat virtual setpoint during highway cruising is up to 105C.

[RMode]

I think the main factor would be noise complaints from owners. Constantly kicking in the fan in and out due to a setpoint that is slightly lower may have customers thinking their car is "extremely loud" with a "fan that runs constantly" and that obviously "can't be right because car X I had before didn't do this". The dual speed e-fan is able to rapidly cool the system, so letting is spike a little higher isn't a big deal.

Another factor may be their foray into "mapped cooling systems" on other cars starting around this time (2000+). On the B6 A4, for example, the thermostat virtual setpoint during highway cruising is up to 105C.

The aux fan is far quieter than the main clutch fan.


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