mustangIIfan

hello i am currently installing an electric fan thermostat on my factory fan, according to instructions i need to splice into a 12v switched power source or the fan will continue to run while car is off, but i was thinking that might not be so bad would the fan eventually turn off when temps go down? will it continue to drain battery?

houtex

Do it like the manual says. If the car is shut off, the temps won't be a problem as there is no excess heat being added. The car is simply going to come down in temperature, and the fan is not needed for that. And running an electric fan on battery alone will drain it. Pehaps not a lot or enough, but, it's not an insignificant power requirement to run those. And I would frankly be a little concerned that the switch might fail, and the fan to run all the time if not switched.

But that's just my opinion on that... whether it's right or not is probably somewhat debatable. Good luck whatever you decide to do!

southcarolina12

electric fans use A LOT of power. when the factory ones on my sierra cut on i can see the head lights dim (for a split second) at night and can hear the difference in the alternator load. it really wouldnt be a good idea to wire it where they will be on if the car isnt on even it will only be on for a min or so. thats just my opinion though.

foxfanatic

It would not benefit anything to allow the fan to run while the car is off.

mustangIIfan

ok thanks for the info guys i wound up wiring it to a 12v switched source on my stereo wiring harness, the wire looked like a 16ga and the wire running to temp probe was a 14ga (so slightly bigger wire) is this gonna be a problem?

houtex

You should instead do this, to ensure you have a good power to the fan.

Get a 30A relay, they are literally all over the place. Here's a reference:
http://shop.advanceautoparts.com/web...archTerm=relay

And also an inline fuse:
http://shop.advanceautoparts.com/web...earchTerm=fuse

Then wire it like this:
http://www.bmwe34.net/E34main/Upgrad...%20diagram.gif

This is the safest way to do the job. The 16 vs 14 gauge wire is then not an issue, because you are not using the incoming 12V switched source as the source for the fan, but a simple signal to switch on the relay, thereby directly connecting the fan's power needs to the battery, and you can use, literally, a 24 gauge wire for that, very low power needs, but whatever is useful is fine. The thermostat will then allow for the signal circuit to complete, as it goes to ground when it senses the temperature is high enough.

And don't worry about 87a, it's not used, you won't need a lamp, just ignore it.

Good luck!

90mustangLX

I wired my electric fan up to a switch with a 40amp relay in between, works like a charm, never just wire it straight up to just a toggle switch, that sucker will heat up in a hurry and possibly start a fire