I generally assume that if the forward/reverse is functioning, then the stator field must be powered. I Also can't get my tractor (I-5) to even move without its field, let alone mow.
Which meter is in the red --- power use meter is what was indicated. What is the fuel level meter indicating while the power use meter is in the red? If both meters are in the red, then the problem is most likely a weak charge.
Are you sure the contactors you replaced were 36v contactors? 12v and 24v contactors "look" the same.
Stay Charged!
Hump
Hot contactors & meter always in the red: I should have thought of this
before... if the field winding is not getting power, the armature &
compound windings will draw huge currents to move the tractor (which may
seem underpowered/slow). I generally diagnose this just "by feel"
(having experienced it before). To check with a meter, you need to
measure the voltage from the diode/varistor card to the "-" on B5. The
card is hard to get at, but look for the end of wire 6A (? what the
drawing says) where it is soldered to the board or the lead of the
varistor (black disk) may be the easiest thing to clip onto. At rest
should see 0 volts; when in either forward or reverse should see ~36
volts (put the tranny in neutral while testing). Others may know easier
ways to test this?