Hay Low:

Just did this on my '83 245 wagon. For me, there was a little box spring clipped to the underside of the dash, up above your left leg. I had to lay on the floor to see it. Mine was not high up, but kind of hidden. There is an aluminum colored spring clip that holds this mechanism up and out of the way. I recognized it by the little speedometer looking cable that went to it. I took a flat blade screwdriver and pryed the clip and out came the box. There was what appeared to be a stainless steel screw hold yet another smaller box down. It looked like and adjustment of some sort as mine had some kind of white seal that looked like it was broken by taking off the screw. Once open, there was a brown bakelite looking button to push down to zero the 30,000 mile counter. I pushed the button down, then unplugged the cable and tucked it safely out of the way. With the maintenance that this '83's getting, there will be no need for any 30K reminders.

Hope any and or all helps!

Sincerely,

JBeechcraft