Dave_eng has posted the Denso voltage drop test several times. Today it saved me a lot of time and some of the few remaining hairs on my head.
Last week, I went to start my M6800, it turned over and just before it started there was a loud pop and nothing. I tried again and all I got was some clicking noise from the starter. Tried to jump start, but no joy. Drug the tractor back to the yard and started ripping things apart. When I had the hood up, there was the distinct aroma of fried circuitry, so I started with testing relays. Relay 1 was toast... from any terminal to any other terminal showed 0 ohms. Tested the other relays and they checked out OK and the fuses were all OK.
Today I received the new relay. Installed and ... no joy. Sigh... well, time to go back to basics for testings, but first the front end loader has to go (it is so easy to remove... when the tractor is running). Used the loader on the Case 780B to lift the loader off the tractor. So much easier to access things when you are not reaching around the loader. Started with cleaning the battery terminals and connectors, there was no visible corrosion, but I used battery cleaner on it dielectric grease when I put it back together. Used contact cleaner for the other end of the positive lead at the starter and dielectric grease when re assembling. Tried again and... just clicking at the starter. I remembered seeing the voltage drop test discussed on this forum, so I went searching for it. Performing the test, the positive lead checked out fine, there was a voltage drop, but my meter showed it going from 0.00 volts to -0.00 volts. Tried on the negative side and got a potential difference of 5.5 volts. disconnected the negative cable where it connected to the frame, there was a little bit of rust between the lead and the frame, but I really didn't think that could be the problem, used some battery cleaner there, took a wire brush the the lead and the frame and re assembled with dielectric grease. Tried again and... she turned right over... I turned the fuel back on (I didn't want the tractor to start while I was testing, so I had pulled the emergency stop) and she started right up. I still can't believe it was just that bit of rust....
Thanks again, Dave.
Last week, I went to start my M6800, it turned over and just before it started there was a loud pop and nothing. I tried again and all I got was some clicking noise from the starter. Tried to jump start, but no joy. Drug the tractor back to the yard and started ripping things apart. When I had the hood up, there was the distinct aroma of fried circuitry, so I started with testing relays. Relay 1 was toast... from any terminal to any other terminal showed 0 ohms. Tested the other relays and they checked out OK and the fuses were all OK.
Today I received the new relay. Installed and ... no joy. Sigh... well, time to go back to basics for testings, but first the front end loader has to go (it is so easy to remove... when the tractor is running). Used the loader on the Case 780B to lift the loader off the tractor. So much easier to access things when you are not reaching around the loader. Started with cleaning the battery terminals and connectors, there was no visible corrosion, but I used battery cleaner on it dielectric grease when I put it back together. Used contact cleaner for the other end of the positive lead at the starter and dielectric grease when re assembling. Tried again and... just clicking at the starter. I remembered seeing the voltage drop test discussed on this forum, so I went searching for it. Performing the test, the positive lead checked out fine, there was a voltage drop, but my meter showed it going from 0.00 volts to -0.00 volts. Tried on the negative side and got a potential difference of 5.5 volts. disconnected the negative cable where it connected to the frame, there was a little bit of rust between the lead and the frame, but I really didn't think that could be the problem, used some battery cleaner there, took a wire brush the the lead and the frame and re assembled with dielectric grease. Tried again and... she turned right over... I turned the fuel back on (I didn't want the tractor to start while I was testing, so I had pulled the emergency stop) and she started right up. I still can't believe it was just that bit of rust....
Thanks again, Dave.
