Automatic electric fan control help

[NFrank89]

Hello All! i've swapped a 351 windsor into my 70 bronco and purchased an electric fan. i want the fan to automatically come on when it needs it and remain on until the coolant temp drops back to where it needs to be. i think the best way to do this is to install a 1 wire on/off coolant temperature switch that shorts to ground once the temperature has reached a certain temperature. (what temp should this be?) then route the wire to the ground side of a standard relay and have the relay turn the fan on.

is this the best way to do it or does it need to be a bit more complex than this? also, where/how do i add this sensor? can i do it inline on a hose?

 

[bluesbish]

I have an adjustable fan control from derale. I think I got it from summitt or jegs. it works just about how you described and also has a bypass that you can wire to a switch to force the fan on. I think the whple kit was about 60 bucks. I know what you are thinking that you can just wire up your own as that was my thought. but I had trouble finding the correct sensor and such and like the adjustability. a lot of guys on this forum are going to tell you that you are wasting time with the electric fan, as they don't seem to do the job unless you have a really god, really big one. I have yet to cruise mine down the road, but so far it is doing the job idling in the shop and moving around the yard.

 

[broncnaz]

Welcome
I hope you have more than just a electric fan to cool that engine. Most aftermarket setups dont work and most poeple endup ditching them. As to your question they sell kits that will do what you want to turn the fan on and off some are even adjustable so you can set the temp it comes on at. I think most come onat around 180 and turn off at 165

 

[G's Baja Bronco]

I got the Painless kit, I ended up using only the sending unit, it is a 180 turn on.

 

[Steve83]

For a single-speed fan, that's all it takes. On my '83, I use a Ford factory temperature switch to trigger a common Bosch/ISO 30A relay. But I also have a more-complex control that allows me to turn the fan off for water crossings & on (low or hi) if the sensor fails. These systems are cheap, easy, & effective:

.

If you don't have a fuel pump relay, tap the LG/R circuit coming off the ig.sw. You can pick it up at the voltage regulator.

 

[NFrank89]

the reason we're going electric is because i dont want the stock fan kicking dirt and shit up into the engine bay when im going through water and mud. any reccomendations for a different fan setup? maybe something out of a car like a civic dual fan

 

[NFrank89]

wheres your temperature switch located?

For a single-speed fan, that's all it takes. On my '83, I use a Ford factory temperature switch to trigger a common Bosch/ISO 30A relay. But I also have a more-complex control that allows me to turn the fan off for water crossings & on (low or hi) if the sensor fails. These systems are cheap, easy, & effective:

.

If you don't have a fuel pump relay, tap the LG/R circuit coming off the ig.sw. You can pick it up at the voltage regulator.

 

[bluesbish]

I went electric for the same reason and I hope it works out. I have a mostly stock 351, stock radiator with 17 inch fan running at high speed. I think it was something like 2400 cfm.

 

[broncnaz]

For the most part the ford taurus fans are the only ones that seem to have a good track record even then a few people have had issues with them. but they seem to be the ones that work the best compared to everything else.
Hit the water and mud hard enough and its going all over the engine bay anyways but I get your point. I would also use caution some of these electric fans dont hold up well to water and mud.

 

[Broncobowsher]

For wiring, run the sender to one pole of a SPDT (OR DPDT and ignore half of it) center off switch. The other pole goes to ground. The common goes the relay. This will give you auto/off/on control of the fan.

As for the temp rating, that gets tougher. First off, what thermostat are you running? Normal operating temperture? The switches have 2 ratings, how hot to turn on and how cool to turn off. If you go too cold the fan will never turn off, go too hot and it will overheat before it turns on. I remember watching a scan tool years ago and with a 192° or so thermostat the turn on was about 215° and off was 205° or so. This kept the fan off so long as there was enough airflow at speed. Only when sitting still and the airflow was low would the fans come on to cool things off.

My personal favorite is a low temp sensor on the lower hose. When the water coming out of the radiator into the engine gets warmer then it should (I think it was a 170° on, 150° off with a 192° thermostat) the fan would kick on. This would keep the engine temp more stable as it never needed to spike to the 215° to get the fan on, but as long as there was enough air to keep the radiator outlet cool enough, the fan stayed off. This is the best set up I ever did on the few electric fan conversions I have done.

If you want to use an off the shelf part instead of an aftermarket switch, here is a huge list of switches that can be had from nearly any parts store.

 

[Steve83]

wheres your temperature switch located?

This pic is linked in the caption of those diagrams:



I chose that spot because it reads the hottest coolant (fresh out of the head) so there's no lag as the engine heats up, and there's always flow thru my heater core circuit - same reason Ford put the ECT there, and the temperature gauge sender nearby.