MF 3070 rpm guage

[Dick Lee]

I have a problem with this guage not working for over 3 years after the local dealer updated the Autotronic 2. The hour meter continues to work fine but needel for rpms doesn"t move. Dealer sold me a new guage after I confirmed that the voltage from the alternator was correct, but I have the same results with new part. I had both guages checked out by an insturment testing shop and the guages are both good. All other functions of the tractor work but not knowing what speed I"m working the equipment bothers me. Is there sensor somewhere else on this tractor and what test/repairs can I preform as the dealer has given up on my problem. Any help or suggestions for this 1986 tractor?
Thanks
 

[oj]

there is an engine speed sensor on this tractor (i think - not sure, i have a 3670 - sort of similar in many ways only bigger) and it has an engine speed sensor, i"ve never changed mine, but as far as i"m aware its mounted on the right hand side of the rear axle housing...

having looked at the online 3070 parts book, there are speed sensors located on top and on the left rear of the diff housing, as far as i can tell, the sensor on top of this housing (screwed into the hydraulic lift cover) is the trans speed sensor, the one on the left rear of the diff casting is the pto speed sensor, and i"d take a stab at the sensor on the hydraulic pump cover being the engine speed sensor, pump cover is located under the right hand cab door (as you sit in the tractor), parts book page 182 - "hydraulic pump cover", sensor is either item # 24 or 30.

hope that helps, good luck, oj
parts book

 

[oj]

just a quick thought...

before you change the sensor, just check the wiring to it, make sure the contact is good between the sensor and the wiring harness, maybe take the wire off and clean everything first and then see it the problem solves itself, done that a few times on my old girl... good luck.