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09-12-2023, 09:17 PM
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CC Member
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Join Date: Jun 2020
Location: SoCal,
CA
Cobra Make, Engine: BDR build #983, FRM 392
Posts: 380
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Not Ranked
Fan won't turn off
This is is on a 2011 build with a 392 Ford Racing motor. The electric fan has consistently turned on and off at temperatures between 90C and 110C. Now, for some reason, it won't turn off, even when the temperature gauge drops just below 90C. Even when driving down the highway and fresh, cold air is flowing through the radiator, the fan stays on, while the temperature gauge is almost close to 80C. When I park the car and turn the motor off, the fan does turn off after about 30 seconds. The motor, which is stock, has 11k miles on it.
Is this a sensor issue? If so, which sensor? The one on the intake manifold near the thermostat housing? Or, the sensor that is on the lower return pipe that runs from the radiator to the WP?
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09-13-2023, 04:40 AM
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CC Member
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Join Date: Feb 2002
Location: Dadeville,
AL
Cobra Make, Engine: Sold my EM.
Posts: 2,459
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Not Ranked
Generally speaking, temp sensors complete the circuit that powers the fan by closing a switch to ground when the temp gets high enough. Either sensor might serve that purpose. One way to figure out which controls the fan is to trace the wire from each sensor and see where it goes. Another way is to disconnect the wire at the sensor while the fan is running. If the fan stops, that is the sensor controlling it. . . . BTW, a loose or frayed wire to the sensor that is inadvertently grounded could also cause the fan to run continuously.
__________________
Tommy
Cheetah tribute completed 2021 (TommysCars.Weebly.com)
Previously owned EM Cobra
"Never attribute to malice that which is adequately explained by stupidity." - Hanlon's Razor
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09-13-2023, 10:54 AM
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Senior Club Cobra Member
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Join Date: Jul 2000
Location: Chilliwack,BC,
BC
Cobra Make, Engine: F5 Roadster
Posts: 1,422
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Not Ranked
relay
Hi,
There should be a fan relay, probably burned/stuck contacts as the fan draws alot of current. Just replace it.
Perry 
__________________
F5 cobra Mark 4 roadster, **SOLD** Ruby Wine Red with pearl,
dual 2" roll bars, warmed up 302, Edelbrock AVS carb and heads, E Street aluminum Heads, Comp cam and roller rockers, AOD, 4.10 Eaton Posi, Power Baer/disc brakes, block hugger headers, 2 1/2" under car exhaust, F500 18" black spoke wheels.
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09-13-2023, 11:40 AM
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Backdraft Racing Dealer
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Join Date: Dec 2004
Location: North Haven,
CT
Cobra Make, Engine: Backdraft Racing
Posts: 5,119
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Not Ranked
Quote:
Originally Posted by SBSerpent
This is is on a 2011 build with a 392 Ford Racing motor. The electric fan has consistently turned on and off at temperatures between 90C and 110C. Now, for some reason, it won't turn off, even when the temperature gauge drops just below 90C. Even when driving down the highway and fresh, cold air is flowing through the radiator, the fan stays on, while the temperature gauge is almost close to 80C. When I park the car and turn the motor off, the fan does turn off after about 30 seconds. The motor, which is stock, has 11k miles on it.
Is this a sensor issue? If so, which sensor? The one on the intake manifold near the thermostat housing? Or, the sensor that is on the lower return pipe that runs from the radiator to the WP?
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The "sensor" on the intake is the coolant temp sender. It's either the thermostatic switch or the relay as we discussed. |
09-13-2023, 11:52 AM
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CC Member
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Join Date: Jun 2020
Location: SoCal,
CA
Cobra Make, Engine: BDR build #983, FRM 392
Posts: 380
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Not Ranked
Fan relay being located around the vicinity of the fuse panel, correct? Is it clearly labeled as 'fan relay'?
Sounds to me like the relay is the easiest and quickest way to start the trouble shooting process.
Last edited by SBSerpent; 09-13-2023 at 12:37 PM..
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09-13-2023, 03:26 PM
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Backdraft Racing Dealer
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Join Date: Dec 2004
Location: North Haven,
CT
Cobra Make, Engine: Backdraft Racing
Posts: 5,119
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Not Ranked
Yes with the fuse box.
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09-14-2023, 03:50 PM
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CC Member
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Join Date: Jun 2020
Location: SoCal,
CA
Cobra Make, Engine: BDR build #983, FRM 392
Posts: 380
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Not Ranked
What I don't understand is why are there two relays when there is only one fan?
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09-15-2023, 03:25 PM
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Backdraft Racing Dealer
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Join Date: Dec 2004
Location: North Haven,
CT
Cobra Make, Engine: Backdraft Racing
Posts: 5,119
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Not Ranked
Quote:
Originally Posted by SBSerpent
What I don't understand is why are there two relays when there is only one fan?
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Earlier Backdrafts had 2 smaller fans. |
09-15-2023, 05:33 PM
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Senior Club Cobra Member
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Join Date: Jul 2000
Location: Chilliwack,BC,
BC
Cobra Make, Engine: F5 Roadster
Posts: 1,422
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Not Ranked
Fuel pump
The electric fuel pump is usually powered through a relay also.
Perry
__________________
F5 cobra Mark 4 roadster, **SOLD** Ruby Wine Red with pearl,
dual 2" roll bars, warmed up 302, Edelbrock AVS carb and heads, E Street aluminum Heads, Comp cam and roller rockers, AOD, 4.10 Eaton Posi, Power Baer/disc brakes, block hugger headers, 2 1/2" under car exhaust, F500 18" black spoke wheels.
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09-15-2023, 06:29 PM
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CC Member
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Join Date: Jan 2009
Location: Las Vegas,
NV
Cobra Make, Engine: Shelby CSX4005LA, Roush 427IR
Posts: 5,574
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Not Ranked
Quote:
Originally Posted by HighPlainsDrifter
The electric fuel pump is usually powered through a relay also.
Perry |
Things like fans and pumps that are switched are almost always relay driven else the wire gauge and switch rating become the current draw of the device...
__________________
Cheers,
Tony
CSX4005LA
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