I am using AtMega 1284p at 3.3v to drive a DC motor through the following two different motor drivers at 12V.
http://www.ebay.com/itm/171442705595
Double BTS7960B DC 43A Stepper Motor Driver H-Bridge PWM For Arduino Smart Car | eBay?
The code is standard code where PWM is driven from 0 to 250.
My problem is at 250PWM the output current is still at about 2.4 amp for both drivers. The heat sink does not even warm.
How can I improve the output. Change the PWM signal from 3.3 to 5v or what?
Thank you for your advice in advance.
Increase the motor supply voltage.
HI,
What are the specs of your motors, how much current do they draw when connected directly to 12V.
Increasing the amplitude of the PWM will not increase the output current.
Gargle PWM motor control basics
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Tom..... 
OK, I will try to use 255 instead of 250. Thank you.
Excellent suggest TomGeorge. Yes find out the current draw of the motor is the key to determine the rest.
I was trying to fix a broken golf cart. I have no idea about the motor spec. How do I test the current draw of a motor. How do I hook it up? Do I just just hook it up to 12V battery. Will it damage it?
Please advise.
I will post a circuit diagram later.
Thank you, Donald
Hi,
Does it have a name plate on the motor that gives any information?
Try 255 as suggested, that will turn the H-Bridge full ON.
How do I test the current draw of a motor.
You have been when you measuring motor current when you measured the 2.4A you quoted in post #1.
Tom....
Hi Tom,
The 2.4A was measured through the motor driver.
I mean to ask whether it is proper, if I hook up the 12V battery directly to the motor, to measure its true current draw.
A digital engineer is afraid of these analog things, as you know. 
Thank you,
Donald