Cooling fan question
Thread Starter
Racer
Joined: Sep 2007
Posts: 369
Likes: 1
From: Calgary AB
Cooling fan question
Is it true, with the AC off, that the radiator fan will not kick on if you are driving over 30-35 MPH? I thought I read this somewhere and if anyone knows for sure, I'd appreciate some solid info. Thanks much
Tech Contributor
Joined: Jan 2007
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From: Dyer, IN
Race Director
Joined: Oct 2002
Posts: 16,477
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
This is kind of tricky to explain, but here goes...
Low speed cooling fans normally shut off at speeds above 35mph, and will turn back on when below 30mph (if coolant temp is above still turn-on setpoint (226°) OR if A/C is on AND coolant temp is above 185°),
If the high speed fans were commanded on, they will not turn off until the turn-off temperature setpoint is reached (227°), or 90mph, UNLESS coolant temp is still above the high speed fan turn-on threshold. (235°)
So it is theoretically possible the fans can be running at any speed.
And this would also indicate a severe problem with the cooling system.
Low speed cooling fans normally shut off at speeds above 35mph, and will turn back on when below 30mph (if coolant temp is above still turn-on setpoint (226°) OR if A/C is on AND coolant temp is above 185°),
If the high speed fans were commanded on, they will not turn off until the turn-off temperature setpoint is reached (227°), or 90mph, UNLESS coolant temp is still above the high speed fan turn-on threshold. (235°)
So it is theoretically possible the fans can be running at any speed.
And this would also indicate a severe problem with the cooling system.
Tech Contributor
Joined: Oct 1999
Posts: 41,032
Likes: 9,790
From: Charlotte, NC (formerly Endicott, NY)
This is kind of tricky to explain, but here goes...
Low speed cooling fans normally shut off at speeds above 35mph, and will turn back on when below 30mph (if coolant temp is above still turn-on setpoint (226°) OR if A/C is on AND coolant temp is above 185°),
If the high speed fans were commanded on, they will not turn off until the turn-off temperature setpoint is reached (227°), or 90mph, UNLESS coolant temp is still above the high speed fan turn-on threshold. (235°)
So it is theoretically possible the fans can be running at any speed.
And this would also indicate a severe problem with the cooling system.
Low speed cooling fans normally shut off at speeds above 35mph, and will turn back on when below 30mph (if coolant temp is above still turn-on setpoint (226°) OR if A/C is on AND coolant temp is above 185°),
If the high speed fans were commanded on, they will not turn off until the turn-off temperature setpoint is reached (227°), or 90mph, UNLESS coolant temp is still above the high speed fan turn-on threshold. (235°)
So it is theoretically possible the fans can be running at any speed.
And this would also indicate a severe problem with the cooling system.
Bill
Race Director
Joined: Oct 2002
Posts: 16,477
Likes: 26
From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
(bottom parameter, highlighted in blue, description at top)
Last edited by Y2Kvert4me; Apr 3, 2010 at 09:06 AM.
