What is the module you refer to? Are you using a plain MOSFET or some sort of MOSFET module? Details please. An FQP30N06L is an N-channel MOSFET and normally Source would connect to GND and Drain to the load. You would also have a resistor between pin and gate. If you have connected it the other way round it's probably dead by now.Steve
The worst-case on-resistance for the FQP30N06L at Vgs=5V is 45 milliohms, which is a lotthese days (10 milliohms is more usual for a low voltage MOSFET).Find a MOSFET with 5 milliohms or so on resistance, and give it a small heatsink,or find one with 10 miiliohms or so and give it a medium sized heatsink, or find two with 10 milliohms and parallel them.You either need logic-level MOSFETs, or you'll have to use a MOSFET gate driver chip running from12V to handle the MOSFET(s). Gate driver chips take logic inputs and drive standard MOSFETs at 12Vwith lots of oomph, essential if using high frequency PWM.Dissipation goes up as the square of current for a MOSFET, so upping the load by a factor of 4means the MOSFET dissipates 16 times more power - which is what bit you. For veryhigh current loads its normal to go for large packages with heatsink, you can even get packageswith screw terminals for 100W dissipations or so.