Low Speed- High Speed fans
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Burning Brakes
Joined: Sep 2013
Posts: 751
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2020 C5 of the Year Winner- Unmodified
Low Speed- High Speed fans
When reading about the radiator fans, it mentions low speed fans and high speed fans. Is this just both fans running at different speeds dictated by the computer settings?
Le Mans Master
Joined: Jan 2001
Posts: 5,022
Likes: 509
From: Hilton NY
In low speed both fans are wired in series so each sees half of the battery voltage, in high speed both are wired in parallel so each sees full battery voltage, to do this three computer controlled relays are used.
Safety Car
Joined: Mar 2005
Posts: 3,759
Likes: 1,218
From: Wisconsin
From the factory service manual:
The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).
The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).
Melting Slicks
Joined: Jan 2009
Posts: 3,275
Likes: 739
From: Miami FL
As explained in Post 2 above, in High Speed Mode full voltage is applied to both fans, while in Low Speed Mode voltage at each fan is reduced to ½.
