Combines 8780 Rotor Speed Sender Trouble

Side winder I believe there is a 5 volt supply to the B terminal from the monitor box, with the plug unplugs to the sender is there 5 volt +_- 1 volt key on thraser switch on and seat switch on. I am assuming that there is rotor reading on the display, if there is rotor speed displayed them the jumper to the constant speed control in bad or messing. Good luck Swtvid

The problem is there is no reading at all on anything.. even if I stick a volt meter on the signal line like where the book says to test it there is 0 volts.. If I remeber correctly the book said it should read battery voltage and then everytime a tooth on the wheel passes the sensor its supposed to cut the voltage off.. or atleast cause a fluctuation in it. I'll check the book again but I'm pretty sure thats what it said Ill double check. I remeber reading about a 5 or 8 volts supply but that was for the 2 wire sensor. but Its something I can look at again... Thanks

I was having problems with my '97 8780 rotor sensor this fall also. I put a new sensor in, but I was getting no reading. So I turned the sensor in the mounting and I was able to get it to work. I figured the little lever that makes contact in the sensor needed to be turned right to be able to pick up the tooth on the gear wheel. The sensor had a flat spot on the threads, but the sensor mount didn't have the flat spot. There are two styles of sensors,I believe. But that's what I tried with the threaded sensor to get it to work in my case.

Ed is there any voltage on pin B with the speed sender unplugIJ Any thing there if the 2 prong plug to rotor speed control module is unplugIJ swtvid

Ya the dealer told me the flat spot has be facing int he diredtion of travel of the rotor (facing the left side),Ed

There is 0 volts on terminal B whether the control modual is plugged in or not. Are you thinkin wires for control modual may have been crimped in backwards or something elseIJ I double and tripled checked everything B4 I even truned the key on. Any other ideasIJ The only thing i can come up with now is either there is something int he wiring harness that I never came across when I was checkin it or the combine monitor isnt regualting the voltage to the sensor (if the monitor is responsible for that),Thanks again, Ed

Ed I am a little confused about B4, on rotor speed control it looks to go in on pin D3. How the speed sensor should work is the monitor has supply voltage going through a current limiting resister (limit current way below 1 amp) from there it is connected to the monitoring part of monitor and to the sensor (coming in to the monitor on pin 2 on plug A1 wire gray_pink) rotor control module is parallel connected on wire form sensor to monitor. The 12 volt sound comes from monitor if any think is no right it wont take much to pull the supply voltage down. If 12 volt was jumper to pin B on sensor it could sort internal transistor. The next step in is to disconnect as close to pin 2 Plug A1 check for supply voltage (12 volt) if nothing there it in the monitor, if it is there its pulling down some place down the wire. I have been work on 8570 that is how the monitor works on it; I am assuming they are very similar excelled 12 volt in steed of 5 volts. The 3 wire sensor uses the 12 volts on pin A to make the primer side of the sensor to work to tern on and off the transistor which sorts pin B to ground when on and not sorted when off. Hope this help. I may need some help a little later, I any work on putting a constant speed control on my 8570. Dee

swtvid: you mentioned you are working at putting a constant speed control on your 8570! let us know how it goes, I'd love to have one on my 8570, I checked around last winter to see if anyone knew how to do it, I had very little luck. 30 miles from here there is a 8570 with the constant speed control, it is the one Massey used in the R and D. No one has been able to get into the control box to see what is in there. The hydro pump and the rotor motor are different than what is on 8570s. GOOD lUCK Neil