Ok do if you do the math with 50 amps and 12 volts the watts come out to 600 watts
With 50 amps and 14 volts it comes out to 700 watts. This should be ok correct? Either way the fuse is rated for 50 amps and i highly doubt the fans will draw that or it wouldn't be safe to be mass produced and sold in to the public correct? Please correct me if I am wrong.

You are forgetting way to much and putting yourself in danger of hurting the car or yourself.. At 12v the battery is almost dead and the alt charges the battery at about 14.4v so you might want to check the math again..

Here check this out
https://bzerob2.wordpress.com/2011/11/15/ford-taurus-2-speed-fan-install/

 

Man I'm kind of set on the fan choice. I've searched around and these ft the radiator better then the Ford will. And they are variable speed capable not a high and low like the Ford deal. Plus i have a charger so these will be backup if the ones in the charger fail. It's the only way i can pass this off to the wife man. If need be i will get two controllers to make it safe. I can't give up on this

 

Man I'm kind of set on the fan choice. I've searched around and these ft the radiator better then the Ford will. And they are variable speed capable not a high and low like the Ford deal. Plus i have a charger so these will be backup if the ones in the charger fail. It's the only way i can pass this off to the wife man. If need be i will get two controllers to make it safe. I can't give up on this

Have you tried searching around cause I doubt your not only one who has done this ??
I will search around later when I have a chance..

 

Yes I have searched. All I've found was the taurus fan and other fans utilizing relays to be operated. but nothing with variable speed only high speed. Another reason Id like to use variable speed is to limit power consumption at idle while maintaining cooling so maybe its best I use two controllers.

 

Well I think I'll just stick with http://www.nastyz28.com/forum/showthread.php?t=200028 as a solution its not variable but what the hey atleast its proven to work. This was my first idea but then I started thinking of a variable speed set-up.

 

instead of using the taurus fan I will use the 2000 Crown vic fan. its wider and should fit better. Also is the same fan/ motoras the mark

 

Why don't you use a thermal fan clutch instead of an electric solution.

See below.
http://www.haydenauto.com/featured products-fan clutches and fan blades/content.aspx

 

I have the factory thermal fan clutch. The electric is a upgrade I've always wanted and provides a couple more mpg. Also cold a lot better when using the a.c. in the summer. I've upgraded the charging system with 2 gauge wire and a 140 amp alternator.

 

I just used a calculator to figure out the wattage given they have a 50 amp fuse. Is there another way to go about this?

A DIY PWM isn't as hard as some are suggesting - you can do it with a 555, there was a circuit posted recently but a quick look round came up empty. If you're interested in going that route, I'm sure someone will put the schematic back up.

Power MOSFETs rated about 50A aren't hard to find, but I'd put 3 in parallel for a generous safety margin and handle standing start surge etc - you can save a few coins by liberating the MOSFETs from a scrap PC motherboard - typical current ranges are about 50 - 70A per device, but the voltage ratings tend to be about 30V - rarely more than 60V, so you have to include catch diode to protect the MOSFET from any back emf generated by the motor. For an automotive electrical environment you also need to protect the MOSFETs from supply transients - modern vehicles usually have devices that clamp to about 68V, that's too much for salvaged PC MOBO parts - either clamp locally to the fan driver or buy 100V MOSFETs.

 

I am very interested in this setup. My choice of fab has me back to a pen control as there is only one leg for a variable speed and not two (high and low)legs like the fan suggested.

 

Have you considered a simple series/parallel switching arrangement? It has its limitations but it may be adequate.

 

I currently have the fan installed using the Volvo fan control . It controls the high and low via two toggle switches inside the truck. It has one 12v input, two 12v outputs, and two negative coil inputs that when activated separately operate either speed. The idea behind the PWM was to allow the lite speed to ramp up slowly so it doesn't draw a bunch of amps on start up. So if anyone has an idea of how i could ramp up the low fan speed id appreciate your idea. Thanks

 

I currently have the fan installed using the Volvo fan control . It controls the high and low via two toggle switches inside the truck. It has one 12v input, two 12v outputs, and two negative coil inputs that when activated separately operate either speed. The idea behind the PWM was to allow the lite speed to ramp up slowly so it doesn't draw a bunch of amps on start up. So if anyone has an idea of how i could ramp up the low fan speed id appreciate your idea. Thanks

The easiest way of implementing slow start is have a control pot and don't turn the knob up too fast.

A PWM controller with current limiting would do the slow start thing anyway - the motor's stall current will be much greater than when its spun up to speed, current limiting will avoid damage and speed will pick up as the motor overcomes inertia.

 

THANKS!