handyrandy 7 #1 Posted March 21, 2020 Looking for a simple engine wiring schematic to get my pair of 312-8 magnums running again. Just a key switch, battery, starter, solenoid, headlights, electronic ignition or whatever it is called. That is all it needs, correct? Thanks! Share this post Link to post Share on other sites
pfrederi 18,679 #2 Posted March 21, 2020 I believe 1986 312-8 would have had a K series with Battery ignition. Magnums use a magneto system. Are you changing engines or had it already been changed to a Magnum,?? 1 Share this post Link to post Share on other sites
handyrandy 7 #3 Posted March 21, 2020 This is what I got. I have two of these tractors that look very close the same year although I a not exactly sure of the year. I was guessing at 1986. They both Run good but the wiring is garbage and giving me problems and I want to streamline the wiring. I also found the attached wiring diagram searching around that looks like it would be close. Thank you for the help Share this post Link to post Share on other sites
gwest_ca-(File Mod) 11,484 #4 Posted March 21, 2020 Your engine was made by Kohler in 1987 so it would land on a 1987 312-8 model 21-12K804 (First year Wheel Horse used spec number 471527) or 1988 312-8 model 21-12K8205 Garry 2 Share this post Link to post Share on other sites
biged77 113 #5 Posted March 21, 2020 I have a 414-8 and 416-8 with magnums and basically identical wiring diagrams. I feel your pain about wiring problems but have been able to troubleshoot and fix issues with safety switches, connections and grounding. If you could detail your wiring issues or symptoms the folks on this site might help you get your 312-8 running and still maintain the safety functions. That said the simple wiring diagram you included will work and the existing switch is correct for this diagram. Note that your model is MUCH simpler than later models which added multiple relays which were hard to access. Ed 1 Share this post Link to post Share on other sites
handyrandy 7 #6 Posted March 21, 2020 Thanks for the help, so is this picture considered a magneto? Share this post Link to post Share on other sites
WVHillbilly520H 10,376 #7 Posted March 21, 2020 Yes, coil/digital ignition module. Magneto. 1 Share this post Link to post Share on other sites
handyrandy 7 #8 Posted March 22, 2020 20 hours ago, biged77 said: I have a 414-8 and 416-8 with magnums and basically identical wiring diagrams. I feel your pain about wiring problems but have been able to troubleshoot and fix issues with safety switches, connections and grounding. If you could detail your wiring issues or symptoms the folks on this site might help you get your 312-8 running and still maintain the safety functions. That said the simple wiring diagram you included will work and the existing switch is correct for this diagram. Note that your model is MUCH simpler than later models which added multiple relays which were hard to access. Ed Thank you I may do that. I am going to clean the tractors and look closer at the electrical systems and try to get tune them up some. The one tractor acts like it has a short when the pto is engaged and wants to spit a little. It runs fine without it engaged. Share this post Link to post Share on other sites
biged77 113 #9 Posted March 23, 2020 The seat switch could be intermittently opening and closing causing the engine to cut out sporadically when the PTO is engaged. The seat switch shuts the engine off (grounds the Magneto) when the operator is not in the seat with the PTO on. The problem could also be a carburetor or engine issue when the PTO is engaged and increases load. You can check the seat switch with an ohmmeter or to rule it out lift one of the switch wires and see if you still have the problem. Ed 1 Share this post Link to post Share on other sites
