Melzi board - bed temperature copying nozzle temperature.

Hello,

I have a mezli 2.0 board that was working fine, but now Btemp is not working and it's copying/sync the Etemp readings with a few degrees in difference, whether the bed is plugged or unplugged.

hotbed is good thermistor is good (tested on a another similar board), bed power is good and can be turned on and off works manually (while btemp is copying etemp readings)
All resistors (1002) R1 R2 R3 to R5 , read approx 10k , but R4 near Btemp reads approx 1.2k (same values as when ends stop shorted) , is there a short somewhere? were to inspect ?

PS:noob in electronics, 3rd world here so a Melzi board is more than technology for me...

Thanks for your message, I replaced the resistor , the problem remains , tried to change btemp sensor pin in the firmware , still copying Etemp readings.
is there a way to heat the bed and control it, by assigning and switching pins with endstops or whatever, I print only in ABS and I need heatbed,

ordered a temp controller from a local store, like this one : [i.ebayimg.com] and the guy sent me a mosfet instead.