Electric Fan Swap Questions

[franklin2]

Assuming its a key on setup then only thing that could cause fan to run with key off is a bad fan relay, it may be under rated for the amps the fan draws so heated up and fused in the closed position
Or the fan motor is going bad and was drawing too many amps, causing relay to fuse closed

AC is a key on circuit so would be off and couldn't trigger the relay

I think I read in a post way up in the thread that the controller he bought is wired to the battery at all times with no ignition off control.

 

[RonD]

The fan can be fused full time power but the relay that is controlled by temp and AC should be key on power, or fan would continue running after you parked the car/truck until heat was below temp threshold

Some vehicles had that setup, but usually had a timer with it so it could only run a few minutes after key off
Or there would be a dead battery in their future, lol
And never understand that thinking, when engine/key is off, there is NO coolant circulation, so cooling the rad coolant with the fan doesn't do much for the engine, lol
I guess maybe the fan in the engine bay would circulate some air, but it would be hot air after coming thru radiator, no, I never did see the benefit of that

 

[rubydist]

There is a small amount of convection circulation of the coolant even with the waterpump not running, but I agree the downside of running the fan with the key off is much greater than the upside.

 

[85_Ranger4x4]

I think I read in a post way up in the thread that the controller he bought is wired to the battery at all times with no ignition off control.

Electric Fan Swap Questions

3 relays No diodes needed

www.therangerstation.com

 

[franklin2]

The fan can be fused full time power but the relay that is controlled by temp and AC should be key on power, or fan would continue running after you parked the car/truck until heat was below temp threshold

Some vehicles had that setup, but usually had a timer with it so it could only run a few minutes after key off
Or there would be a dead battery in their future, lol
And never understand that thinking, when engine/key is off, there is NO coolant circulation, so cooling the rad coolant with the fan doesn't do much for the engine, lol
I guess maybe the fan in the engine bay would circulate some air, but it would be hot air after coming thru radiator, no, I never did see the benefit of that

I ran my first setup straight to the battery. Depending on the outside temp, it would cycle on and off after I turned the key off. It never ran the battery down and it seemed to help heat soak on the carb a little bit, that may have been my imagination. It did cycle on and off, so that tells me it did have some circulation in the coolant with the engine off. I had the probe inserted in the coolant loop to the heater core.

I transferred this setup to the 2.8 Bronco II I have now, and during the hottest weather climbing the mountain everyday, it would get up to 230 on the temp gauge. So I swapped back to the mechanical fan and it kept it cool, not getting over about 215 on the worst days. But the mechanical fan was noisey and put a lot of load on the engine. When you only have about 100 hp, taking anything away from that is noticeable.

I started looking for a better electric fan for cheap. I found a 2 speed Taurus fan at the local junkyard for $35. A little cutting and trimming and it fit. I had done some experimenting, the aftermarket 16 inch fan I had pulled about 10-12 amps. I checked the Taurus fan on low speed, it was pretty lazy and only pulled 8 amps. I knew that would not be enough. I tried high speed, but my meter only went to 15 amps and it blew the fuse in it. When I touched the high speed wire to the battery, it made a pretty good spark initially. I was afraid it would ruin my cheap full voltage thermostat I was using, so I did add a relay to handle the extra current. I used the power from the emissions vent solenoid on the carb to power the thermostat and relay for the control power.

So I am using high speed only on the Taurus fan. I works very well so far. I have it set to come on at about 215. The engine has a lot more pep now it's not turning the mechanical fan all the time. I was worried about the stock alternator turning the Taurus fan at high speed, but it does fine. And with the relay it does cut off now when I turn the key off. I went ahead and took the A/C system off, so that extra bit is not needed on mine for now.

 

[Dirt Squirt]

I needed to run my fan on my Mustang in the staging lanes at the drag strip to cool down between rounds as much as possible without running engine. Did make for some interesting times needing a jump start in final round a couple times though.

 

[360alaska]

This is the circuit I plan to use:

3 Bosch style relays and a 40a fuse.