electric fans - cool down after engine off

[cjohnson6772]

Fired my engine up for the first time night before last. Everything looks to be checking out great! I have a question about the elec fans though. I'm running fbody dual fans through the pcm control. The first fan is set to come on at 185 and I'm not sure where the second is set :\ Sitting in the shop idling the engine is running at 200-204 and the primary fan runs fine but the second fan only twitches. It does not engage, but it is definitely moving some. To eliminate the possibility of a bad fan motor I swapped the plugs and then the secondary fan runs fine. I think it has to be the connector that plugs into the second fan is just bad?!?!? Why would the fan just twitch though and not fully engage?

My main question though: is it possible with just a pcm and no bcm to tune the computer to run the fans to cool the engine down after the truck is cut off? Right now my fans cut off as soon as the engine dies. Any wiring mods needed? Or just something in the tune?
Posted via Mobile Device

[clinebarger]

No need, Without water flowing the fan will not cool the engine.

[cjohnson6772]

Originally Posted by clinebarger

No need, Without water flowing the fan will not cool the engine.

You do make an excellent point. But for the sake of argument why does the factory do it? Must be some benefit? How hard would it be to implement? I do appreciate your point and will probably subscribe to the philosophy of don't fix a problem that doesn't exist....but I would like to know just because....
Posted via Mobile Device

[ls1nova71]

They are not supposed to run after the engine is shut off. The factory used to do that, but not any more, at least on GM LS engines. I think they realized it wasn't really helping like Cline said. As for your second fan not coming on, check your tune to see what temps it's set to come on and go off at. I've seen a lot of people have the second fan relay just click on and off, and the think that it has to be a tune issue.
Posted via Mobile Device

[Critter]

Cline is right about it not doing any good without the water pump turning. I have often wondered if the fans being on would move a little air under the hood and help some, if so its probably minimal.

To answer your question though, Yes the ecm can be programmed to run for a period of time after the key is turned off.

[cjohnson6772]

Originally Posted by Critter

Cline is right about it not doing any good without the water pump turning. I have often wondered if the fans being on would move a little air under the hood and help some, if so its probably minimal.

To answer your question though, Yes the ecm can be programmed to run for a period of time after the key is turned off.

Yeah it makes sense about it not helping much. I am getting my tune finished on the dyno this Saturday and I'll ask the tuner. If it is easy I may have him do it anyways. It can't hurt right?
Posted via Mobile Device

[Critter]

I use EFI Live and it's very easy, not sure what your guy uses but I'm sure it's simple regardless.