electric fan switching?

[jekbrown]

I've seen lots of people's electric fan wiring diagrams and was wondering if there is a good reason not to just have a simple manual switch on a ignitions-on circuit and call it good. Why even mess with all the thermostats and everything? The manual switch would be there to shut down in case of water crossing... other than that, when would I want it off?

j

 

[1979jimmy350]

because at lower speeds and when it is really cold out the fan is not needed, if the fan was on all the time the engien would take a lot longer to warm up, it is simlar to the clutch on most manual fans nowadays

 

[wraenking]

and its easy. a couple of 30 amp relays and a couple of 30 amp circuit breakers is all you need, plus the thermostat connection. i have mine so the small fan goes on with ignition, and the bigger one kicks on with the temo sender

 

[ntaj*ep]

What has been said plus its moron proof. You don't burn out the motor prematurely and wear on your cherging system. Also you can wire with a 3-way switch so you can have it run on all the time, with the thermistor switch or off. Way more conveient.

 

[sled_dog]

Look at my thread on the thermostatic switches. Some are sub $60 and come with relays(which you need either way). For a quicker warmup and no worries on flipping a switch, seems a good idea to me, especially if it gets the relays out of the way too. I will likely put a failsafe switch in, if I notice the temp is getting high and the fans aren't running, flip the switch and figure otu the problem later.

 

[dyeager535]

Warmup is not affected by fans. The thermostat governs the engine temp. Yes, I tested this by forcing a fan on while engine was warming up, and while off. Look at it this way...you are increasing the load (heat production) on the engine if the fan is running.

Benefits of a temp switch are that you can't forget to turn the fan on (or anyone that drives it) and if it matters, the engine consistently is cycled through the exact same temp range.

The only reason NOT to be on a temp switch solely is because of water crossings. As mentioned, a switch that still allows you to kill the fan for water crossings would be the plus for wheelers.

My testing with my 355 showed that I didn't need a fan at all over about 20MPH. Airflow from vehicle speed alone was enough to cool it, if the fan were running I'd be wasting power by putting the load on my charging system. That's unloaded on fairly flat ground. At a light it was obvious you need a fan pretty quickly.

As it is I've got a 78amp alt that runs my truck and it's enough. Injection helps to compensate, but both fans are a large load on the engine.