MK2B heated bed only half heating

[iras]

I bought a used Prusa i3 that I'm in the process of learning and cleaning up along the way.

Only half the heated bed seems to be getting hot. Looking at the MK2B bed, it looks like there might be two heating elements, which can be connected in series (Pins 2 and 3) if powered by 24V and in parallel (Pins 1 and then 2/3 tied together) if powered by 12V.

Checking the connections, it looks like pin 2 isn't connected, so only 12V is going to 1 and 3 - half the bed!

QUESTION: If I tie in pin 2, I'm doubling the current requirements on the RAMPS 1.4 board. Will I burn it out? My power supply is rated at 12V 20 Amps, so it looks like the power supply is sufficient. But I don't know the specs on the RAMPS 1.4 board D8 connection, and I also don't know the power requirements for the MK2B.

Thanks.

[printbus]

RAMPS D8 is protected with an 11-amp polyfuse. Overcurrent will cause the fuse to heat and open. When it cools, it closes and applies power again. MK2B is spec'd as 1 to 1.2 ohms in 12V configuration. Ignoring wiring losses, this is 10 to 12 amps. You're likely fine especially after allowing for resistance in the wiring from the power supply to RAMPS and then from RAMPS to the heat bed, and for the on-resistance of the MOSFET switch itself. Do make sure the power supply, if adjustable, is set for 12V and not something like 13.8V.

[iras]

Thanks. Wanted to be sure before connecting.