handyrandy 7 #1 Posted April 4, 2017 I bought another 312-8 last week to mow my family's grass at the home place, and I am working the bugs out of it. One bug is that it wont shut off when I turn the key to off. I first thought it was the ignition switch but it checks out with the meter. However the black wire that attaches to the ground lug on the ignition switch is not grounded to the frame for some reason. Could this be the problem? Thanks! Randy BriansWiringDiagram.jpg-original 103991backterms.gif-original 2 Share this post Link to post Share on other sites
953 nut 51,018 #2 Posted April 4, 2017 Bingo! The black wire will ground out the Mag when the key is turned off or when you get off the seat while the PTO is on. 4 Share this post Link to post Share on other sites
Lee1977 6,175 #4 Posted April 4, 2017 The ground lug on the switch is grounded to the switch case if you have the right switch. I have had trouble with starting and found the screws holding the dash plate rusted and not making good ground. That was starting only didn't affect shutting down. 1 Share this post Link to post Share on other sites
handyrandy 7 #5 Posted April 4, 2017 Oddly enough, although the lug is right against the switch case there is no continuity. How two pieces of metal could be touching and not connected is strange. Another oddity I found is all the new replacement switches I have found have the ground lug marked as a 3 instead of a G in the product photo. Thanks for the replys. Share this post Link to post Share on other sites
Lee1977 6,175 #6 Posted April 5, 2017 I had my 312 out yesterday to clean the yard of limbs. When I shut it down I kept running. Tried the switch a couple of time it kept running, pushed hard on the key and it stop off. My switch is loose in the case or the contacts or worn. I won't mention the other quirks I found with it yesterday they may be catching! If it is an original switch it 28 years old I think tractor is a 1989 the tag was gone when I got it. That was the first time it didn't shut down. 1 Share this post Link to post Share on other sites
953 nut 51,018 #7 Posted April 5, 2017 1 hour ago, Lee1977 said: I had my 312 out yesterday to clean the yard of limbs. When I shut it down I kept running. Tried the switch a couple of time it kept running, pushed hard on the key and it stop off. My switch is loose in the case or the contacts or worn. I won't mention the other quirks I found with it yesterday they may be catching! If it is an original switch it 28 years old I think tractor is a 1989 the tag was gone when I got it. That was the first time it didn't shut down. Here is a copy of your wiring diagram, it might help. 1 Share this post Link to post Share on other sites
JC 1965 1,527 #8 Posted April 5, 2017 My neighbor was having trouble with an ignition switch on his Ford tractor. He came to the conclusion that it was a ground problem with the switch. So he ran a separate wire from the back of the switch ( where it mounts to the sheet metal ) to the tractor frame and it works great now. 2 Share this post Link to post Share on other sites
handyrandy 7 #9 Posted April 5, 2017 I ran a new ground from the switch to the frame and now it works perfect. Thanks for all the help. Randy 2 Share this post Link to post Share on other sites
953 nut 51,018 #10 Posted April 5, 2017 1 minute ago, handyrandy said: now it works perfect. 1 Share this post Link to post Share on other sites