You could use an auto headlight as the dummy load for testing. They draw only 5A or so, but you could put more in parallel if you want to draw a higher current. They have the advantage of visual feedback.
Just a word of caution - 25A is a LOT for any beginner project. I suggest starting with a small 12V bulb and move up in power only slowly, after you confirm safe (and not hot MOSFET) operation at lower currents.
I have tested the circuit already with the fan running for a couple minutes. i just want to run it for a 24 hour cycle. I was thinking of getting a 300 watt resistor from Digikey but was unsure if that will work. And if so what value.
How about some other opinions, tonight?
It'll be in the mail tomorrow.
I have .5, 1, 2, and 4 ohm.
From OP:
" I am unsure of what ohm's I need. I am working on a 12 volt system actually 13.8. I want to create 25 to 50 amp loads simulating a fan that is powered by a PWM controlled MOSFET. What would you suggest?"