I have recently purchased a 1998 4890 windrower. It has the rocker switch throttle control on the armrest and, I believe, it is supposed to function as a 3-position switch (idle, medium level throttle, and wide open/max rpm). Currently it only operates on idle or max rpm.

Questions: 1. Am i correct in my understanding this machine should have three engine speeds as delivered by JD?

2. Would it be possible, relatively easily, to replace the rocker switch throttle control with a potentiometer such as that out of a late model JD tractor?

If, in my first question, I am correct (it should have 3 engine speed positions - the rocker switch certainly does), I can ohm out the switch and other components to diagnose what isn't functioning properly there (i.e. no middle engine speed function) and fix that. However, if there isn't some proprietary programming in the computer or elsewhere that would make installing a potentiometer difficult, I would sooner go that route.

Anybody with advice, thoughts, or attempted such (or on a similar machine) before?