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Old 11-13-2017, 02:30 PM   #1
nikwho
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How to wire electric fans to stay on for a few minutes after engine is shut off?

Hello all,
I've currently got my electric fans wired to a relay with the trigger wire hooked to a constant 12v, switched by a 180°temp switch, so that the fans continue to run after I shut down. However, my radiator doesn't have a bung for the temp gauge, so the fans run until the coolant in the intake manifold is under 180°, which takes a fair bit of time. I don't want to end up with an issue that drains my battery, so I'm wondering how to wire this thing so that it runs for a set amount of time after I shut down? Is there anything that I can install that gets 12v and shuts piwe off after a set amount of time after it stops receiving power from the ignition?

Thanks,
Nik
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Old 11-13-2017, 02:55 PM   #2
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Re: How to wire electric fans to stay on for a few minutes after engine is shut off?

I've got delay off headlight kits available and the same method of activation could be used for your cooling fan(s) as well. Its more of a race oriented relay control fan harness but it would do what you want. Its a solid state circuit design and is adjustable from 0-900 seconds after ignition off, for example.
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Old 11-13-2017, 04:21 PM   #3
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Re: How to wire electric fans to stay on for a few minutes after engine is shut off?

That sounds like something that would work! Have a link or any more information?
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Old 11-15-2017, 10:29 AM   #4
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Re: How to wire electric fans to stay on for a few minutes after engine is shut off?

There is a time delay relay that will do this.
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Old 11-16-2017, 10:41 PM   #5
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Re: How to wire electric fans to stay on for a few minutes after engine is shut off?

In my opinion it is a waste of time and energy to run the fan after the engine is shut off.
The fan will only cool the liquid in the radiator because the water pump will not be sending fresh hotter coolant into the radiator. The cooling effect will be done by thermal conduction from the hot manifold coolant to the radiator until the thermostat closes, and what can cool from heat flow from the water pump. This will take some time and it will cool anyway as the engine block cools.
I would just rewire the relay to shut down with the key and the cooling sensor.

Does anyone know if the car manufacturers are setup for the fans to run after engine shutdown?
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Old 11-17-2017, 12:33 AM   #6
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Re: How to wire electric fans to stay on for a few minutes after engine is shut off?

For some reason I thought the OP was running an electric water pump too-but I guess not. If you were, you could run 2 control relays together for the fans and water pump to be triggered with delay via a solid state relay-but if running a mechanical fan then as Vette said-not worth the effort.
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Old 11-18-2017, 01:49 PM   #7
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Talking Re: How to wire electric fans to stay on for a few minutes after engine is shut off?

Late model fans can come on anytime the set points are over the setting without the key on.

I have mine wired with a temp probe in the 64 and 56 that will allow the fans to stay on until the temp is below the on set point.
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Old 11-23-2017, 11:49 AM   #8
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Re: How to wire electric fans to stay on for a few minutes after engine is shut off?

why would one want to continue to cool the water in the radiator after the engine is stopped?
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Old 11-23-2017, 12:49 PM   #9
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Re: How to wire electric fans to stay on for a few minutes after engine is shut off?

For the majority of people its a drag race thing-cooling it off between runs after sitting and running waiting to run. For the street while it'd be cool to do (pun intended!) theres not a good way to run an electric water pump.
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Old 12-08-2017, 07:46 PM   #10
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Thumbs up Re: How to wire electric fans to stay on for a few minutes after engine is shut off?

The probes are set to kick the fan on low at 180* automatic. If the car is over 180* when you turn the key off it will run until it cools it down enough.
It so I don't have to worry about a switch on the dash to do it myself.
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Get out and drive the truck this summer and have some fun!
It sucks not being able to hear!

LWB trucks rule, if you don't think so measure your SWB!
After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.
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Old 12-08-2017, 07:55 PM   #11
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Re: How to wire electric fans to stay on for a few minutes after engine is shut off?

Just fyi...push-in style probes are accurate to +\- 10 degrees whereas a temp switch is +\-3 degrees. Sounds like you basically have the fan wired the way which works for ya-are you using a deep cycle battery or no?
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