James Combs
04-29-2018, 12:18 PM
I have a small problem, just thought I would get some other input.
Background:
I have two rider mowers, an old 73 vintage Craftsman that I use as a tractor and a 6-8yr old Troy-Built Bronco which I do the mowing with. Both have Briggs engines and both have carburetors that leak and will fill the crankcase with gasoline if I don’t turn the gas off to the carb someway. Have installed manual shutoffs on both machines which has worked well except when I forget to turn the valve off. Given my sometimes forgetfulness I have purchased a couple 12volt fuel rated solenoid valves to do the for me automatically since I seem to be loosing my memory functions:rolleyes:. Adding valve will not be a problem on the Troy-Built because there is a 12volt anti-after-fire circuit going to the carb which I can tap into. The anti-after-fire circuit is supposed to keep the engine from doing that big backfire like noise when you turn it off, it has 12volts available anytime the ignition is on. However, the old Craftsman does not so I needed a new ignition switch with additional contacts to do the same thing.
The Problem:
I purchased a “MaxPower 9623 Ignition Switch” which should have done the job, however, while checking it to verify that continuity through the contacts was compatible with my old Craftsman switch which should have been the case, I discovered what I think is a problem/defect with the switch. If you research lawn mower ignition switches you will find that “most” have the same IDs on the connector terminal lugs on the back of the switch. For example, most will have a “G” for ground, “B”-battery, “M”-magneto, “L”-lights and “S”-start stamped next to the appropriate terminal. Others may add “A”-auxiliary1 and “Y”-auxiliary2 or they may be A1 and A2. By hooking up my ohm meter to various combinations of these terminal lugs I can verify continuity between any two given terminals depending on the position of the switch key. I have included a copy of a graphic representation of the internal connections of a switch I found on line which for the most part matches the new switch except in one area. I have added dashed red lines to the “Start” position graphic which shows the difference and the problem. In my experience G and M should never be connected together except in the off position. Any time M is connected to G or ground the magneto is in “Killed” or off status which kills the engine, that’s exactly how the engine is shut down when the key is turned to the off position. The engine will never start with this switch?? Unless there is something I am missing in the design of more modern mower ignition systems this switch is defective. I have also included a short video of me testing the G and M terminals.
Question:
Is there anyone out there that can confirm for me that this is a defective switch or that it is correct and just works differently in today’s more modern ignition systems? If it is correct I would sure love to see a circuit diagram or schematic showing how it is used.
This pic is a graphical representation of the internal connections of the switch. All positions are ok and match my old switch except the last position, "Start", the dotted red should not be there, also my old switch does not have A&Y.
384942
I appreciate any and all comments and feedback.
As it turns out I could use the L circuit on my old switch except it is ~40yrs old or so. My old Craftsman uses a separate light switch and not the L circuit. I will be using a new switch in any case but it doesn't look like it will be this one.
Just bought another switch, a Stens 430-674 which according to cross-differences should be the same as the MP 9623. When I get it I will post what I find out about the Stens' start position circuits. Oh and BTW, truth tables, graphics like the above and other contact info for compatible switches that I have been able to find do not show the G to M connection. For example this circuit for a Murray mower uses a similar compatible switch.
The 95226 switch shown in the lower corner crosses to the Stens 430-674 and to the MP 9623. My MP would not work in this circuit.
Note the terminal truth table below the switch.
384944
Background:
I have two rider mowers, an old 73 vintage Craftsman that I use as a tractor and a 6-8yr old Troy-Built Bronco which I do the mowing with. Both have Briggs engines and both have carburetors that leak and will fill the crankcase with gasoline if I don’t turn the gas off to the carb someway. Have installed manual shutoffs on both machines which has worked well except when I forget to turn the valve off. Given my sometimes forgetfulness I have purchased a couple 12volt fuel rated solenoid valves to do the for me automatically since I seem to be loosing my memory functions:rolleyes:. Adding valve will not be a problem on the Troy-Built because there is a 12volt anti-after-fire circuit going to the carb which I can tap into. The anti-after-fire circuit is supposed to keep the engine from doing that big backfire like noise when you turn it off, it has 12volts available anytime the ignition is on. However, the old Craftsman does not so I needed a new ignition switch with additional contacts to do the same thing.
The Problem:
I purchased a “MaxPower 9623 Ignition Switch” which should have done the job, however, while checking it to verify that continuity through the contacts was compatible with my old Craftsman switch which should have been the case, I discovered what I think is a problem/defect with the switch. If you research lawn mower ignition switches you will find that “most” have the same IDs on the connector terminal lugs on the back of the switch. For example, most will have a “G” for ground, “B”-battery, “M”-magneto, “L”-lights and “S”-start stamped next to the appropriate terminal. Others may add “A”-auxiliary1 and “Y”-auxiliary2 or they may be A1 and A2. By hooking up my ohm meter to various combinations of these terminal lugs I can verify continuity between any two given terminals depending on the position of the switch key. I have included a copy of a graphic representation of the internal connections of a switch I found on line which for the most part matches the new switch except in one area. I have added dashed red lines to the “Start” position graphic which shows the difference and the problem. In my experience G and M should never be connected together except in the off position. Any time M is connected to G or ground the magneto is in “Killed” or off status which kills the engine, that’s exactly how the engine is shut down when the key is turned to the off position. The engine will never start with this switch?? Unless there is something I am missing in the design of more modern mower ignition systems this switch is defective. I have also included a short video of me testing the G and M terminals.
Question:
Is there anyone out there that can confirm for me that this is a defective switch or that it is correct and just works differently in today’s more modern ignition systems? If it is correct I would sure love to see a circuit diagram or schematic showing how it is used.
This pic is a graphical representation of the internal connections of the switch. All positions are ok and match my old switch except the last position, "Start", the dotted red should not be there, also my old switch does not have A&Y.
384942
I appreciate any and all comments and feedback.
As it turns out I could use the L circuit on my old switch except it is ~40yrs old or so. My old Craftsman uses a separate light switch and not the L circuit. I will be using a new switch in any case but it doesn't look like it will be this one.
Just bought another switch, a Stens 430-674 which according to cross-differences should be the same as the MP 9623. When I get it I will post what I find out about the Stens' start position circuits. Oh and BTW, truth tables, graphics like the above and other contact info for compatible switches that I have been able to find do not show the G to M connection. For example this circuit for a Murray mower uses a similar compatible switch.
The 95226 switch shown in the lower corner crosses to the Stens 430-674 and to the MP 9623. My MP would not work in this circuit.
Note the terminal truth table below the switch.
384944