MOSFET test help

Thread Starter


Joined Apr 22, 2013
I have a PWM fan control and I am trying to bench test the MOSFET I chose.

It will be a 12VDC system and the fan will pull 25amps. Any thoughts on how to do this without having to connect the fan itself up?


Joined Sep 9, 2010
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.

Thread Starter


Joined Apr 22, 2013
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.


Joined Nov 7, 2013
Op wants 4 resistors from the flea market.

Isn't sure what values he needs.

I'm thinking 4 - 1ohm. 300 watt.

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?"
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