Quote Originally Posted by JD5210 View Post
Is there power on the red wire? The role of #385 is to activate the relay, so power from the red wire can be used to power the heater. As already suggested double check the fuses.

At least on my tractor there is NO light on the instrument cluster to indicate the heater is activated, the charging system light does dim a little, when the key is pushed in.

If there is no power on the #385 as you have said, I suggest you follow 385 back to the key switch and see if there is power at the switch and using an ohm meter check 385 from the key switch to the relay.
The above description is exactly what happens on my 5303. I make one click to the right before the "crank" position then push in the key and see the charging light dim. Have tried cranking in cold weather both with and without using heater and it definitely makes a difference.