I had a simular problem with my 312A model ... but the govenor failure was due to the rad not cooling out the engine enough ... it caused the engine compartment to have way to much excessive heat build-up, eventually melting the sleaves where the throttle cables slide thru and binding up and then seizing up the cables and burning out the govenor motor
Got the new pricey govenor motor c/w cables (the only way you can buy it) and installing it ..... then the Cat product support guy came by and did as mentioned, went into the program mode and set it up ..... next time it heated up I could tell that the throttle became not very responsive (kinda sluggish) ... when I shut it down the damn cables seized again .....I was lucky tho and was able to free them up .... that's when we found out after alot of farting around that it was the rad and not : the thermostat, not the sensor, not the rad cap, not the gauge, not the water pump... ect.
Finally replaced the pricey rad (which I must have been the only guy to ever replace a 312 rad, so told) which had to be ordered and shipped from the back east warehouse (extra cost to ship) .... but after all of this its been 4yrs now and it works flawlessly .... wouldn't trade the 'ol Cat for nutt'n cept for maybe a newer 314CL w/air .....LOL ...... JMLS .....:drinkup