Rad Fan question.

[Shawn519]

Recently purchased a F5 Roadster that was completed but needed a little bit of work.

Currently, the rad fan comes on at 80 and functions fine. However after engine shut off, it will run for a long time if the master is not turned off.

Unless I misunderstand this is bc coolent stops circulating, so it heats up near the thermometer and takes while to cool down. That said, the fan, blowing air on the rad is doing absoultly nothing bc the coolent is not circulating.

Should i have an override switch to disable the fan or am i missing something? Or if the engine temp is fine just kill the master ?

Just doesnt seem right that you can run the car, temps are all perfect then when you turn off the car the fan wants to run for 10-20m. (=

[42Bfast]

I can’t speak to your specific application but it sounds like the fan is on a HAAT(Hot at all times) circuit. You can change that to a circuit that is only hot when the ignition switch is in the “On” position. The fan will then shut off when the engine is shut down.

Of course, you can, as you mentioned, just continue to shut it off with the master. If you choose this path, depending on your specific configuration, I would suggest installing a keep alive jumper to keep EFI/computer memory as well as dash clock etc powered.

I know of no significant reason to keep the fan running after the engine has been shut down. As you noted the coolant doesn’t circulate so it doesn’t benefit the engine. (If someone has better information, please correct me if I’m wrong.)

I wouldn’t recommend a separate switch that shuts off the fan, mostly because it’s too easy to forget to switch it back on when starting up again, obviously risking an overheating issue.

[CraigS]

We don't know specifically how your rad fan is controlled but this is a generic diagram for the relay.
189495
The pin marked 'coil trigger' is the power to operate the relay. If it goes to a HAAT power source, like 42Bfast mentions, you will have what you have. You can switch it to a 'key on' source and solve the problem.

[Shawn519]

Thanks guys.

REwired to an ignition only source and now funcitons as i had expected. Guessing it was jut an oversight with previous owner.

[rich grsc]

Thanks guys.

REwired to an ignition only source and now funcitons as i had expected. Guessing it was jut an oversight with previous owner.
Not necessarily, that is an option to wire it that way. The fan running after shut down will help cool the engine. The coolant will thermo-syphon through the radiator for a time.

[Jeff Kleiner]

Thanks guys.

REwired to an ignition only source and now funcitons as i had expected. Guessing it was jut an oversight with previous owner.

Actually the earlier FFR harnesses from Ron Francis were setup so that the fan was only hot with the ignition on however a few years ago they were reconfigured to be hot at all times like yours. I don't know what prompted the change but when I build with the newer harness I change them over so that the fan shuts off when the ignition is off.

Jeff

[FLPBFoot]

I wanted control over the fan. Installed a 3 position switch so I can set the control to Thermostat, Off, or On. Thermostat most of the time except when I roll into a show or garage where I shut it off and open the hood. Hooking it to the ignition will shut it off in those situations but I've also found when I want to work on the car after a drive, putting it to the On position will cool as Rich gsrc said and it also blows air in the engine bay cooling the motor quicker.