Need Help with troubleshooting ignition switch on Murray 12.5 HP

EngineMan

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  • / Need Help with troubleshooting ignition switch on Murray 12.5 HP
As you say and you are right, if any of the safety switch(s) are open, there will be no path for power(12v+) to go to solenoid. that is why you need to check all safety switch(s) one by one until you find the one (maybe two) that are open.
I have no plans in leaving you until you have fix it, or you have given up on it. so keep working at it:thumbsup:
 

EngineMan

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  • / Need Help with troubleshooting ignition switch on Murray 12.5 HP
This may also help you, work out by two good member's on this site.

Electrical* problems can be very easy or very difficult, depending on four things.
1. * How well you understand basic electricity.
2. *What tools you have and know how to use.
3. *How well you follow directions.
4. *You don't overlook or assume anything and verify everything.

Remember we cannot see what you are doing. *You are our eyes, ears and fingers in solving this problem. *You must be as accurate as you can when you report back. *The two basic tools we will ask you to use are a test light and a multi-meter. *If you have an assistant when going through these tests it would be very helpful. *These steps work the best when done in order, so please don't jump around. *Now let's solve this problem.

First, check the fuse(s), check battery connections for corrosion (clean if necessary) and *voltage - above 12.5 volts should be good.*

Second, check for power from the battery to one of the large terminals on the solenoid. *One of the wires is connected directly to the battery and has power all the time so one of the large terminals should light a test light or show 12 volts on a meter at all times.*

Third, *check for power at the small terminal of the solenoid while depressing the clutch/brake pedal and holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch). If your solenoid is a four wire solenoid, check both small wire terminals as one is ground and the other is power from the ignition switch. *If your solenoid is a three wire solenoid, make sure the solenoid body is not corroded where it bolts to the chassis of the mower as this is your ground path back to the battery. *If in doubt, remove the solenoid and clean the mounting area down to bare metal. *If there is no power to the small terminal then your problem is most likely a safety switch, ignition switch or in the wiring.*

Fourth, check for power on the other large terminal of the solenoid while holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch).*

Fifth, check for power at the starter while holding the key in the start position (assistant again).*

Sixth, check your ground circuit back to the battery.

After you have gone through each of the above steps, let us know what happened when you did each step. *At that point we will have great info to tell you how to proceed. *Remember you are our eyes, ears, and fingers, so please be as accurate as possible.

Be as specific as possible with voltage readings as this will help diagnose your problem quicker. *If you do not know how to perform the above checks, just ask and I will try to guide you through it. *Youtube also has some videos and as you know a picture is worth a thousand words.
 

MTD

Member
Joined
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  • / Need Help with troubleshooting ignition switch on Murray 12.5 HP
As you say and you are right, if any of the safety switch(s) are open, there will be no path for power(12v+) to go to solenoid. that is why you need to check all safety switch(s) one by one until you find the one (maybe two) that are open.
I have no plans in leaving you until you have fix it, or you have given up on it. so keep working at it:thumbsup:


EngineMan, you asked me specifically earlier in the thread:

You can check this by taking off the small lead on solenoid and seeing if you have battery volts on the lead when key is in start.


Please try and understand what I am asking:

Look at the diagram:

You will see that the PTO is NORMALLY OPEN in the starting position. Normally opens means there will be NO VOLTAGE passing through the circuit. so,

WHY SHOULD I EXPECT TO READ FULL BATTERY VOLTAGE ON THE SMALL SOLENOID WIRE WHEN TURNING THE KEY TO START WHEN THE PTO IS AN OPEN CIRCUIT IN ITS STARTING POSITION?
 

EngineMan

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  • / Need Help with troubleshooting ignition switch on Murray 12.5 HP
I am with you and do understand what you are saying, that switch (circuit) need's to be closed.
 

MTD

Member
Joined
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Threads
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  • / Need Help with troubleshooting ignition switch on Murray 12.5 HP
This may also help you, work out by two good member's on this site.

Electrical* problems can be very easy or very difficult, depending on four things.
1. * How well you understand basic electricity.
2. *What tools you have and know how to use.
3. *How well you follow directions.
4. *You don't overlook or assume anything and verify everything.

Remember we cannot see what you are doing. *You are our eyes, ears and fingers in solving this problem. *You must be as accurate as you can when you report back. *The two basic tools we will ask you to use are a test light and a multi-meter. *If you have an assistant when going through these tests it would be very helpful. *These steps work the best when done in order, so please don't jump around. *Now let's solve this problem.

First, check the fuse(s), check battery connections for corrosion (clean if necessary) and *voltage - above 12.5 volts should be good.*

Second, check for power from the battery to one of the large terminals on the solenoid. *One of the wires is connected directly to the battery and has power all the time so one of the large terminals should light a test light or show 12 volts on a meter at all times.*

Third, *check for power at the small terminal of the solenoid while depressing the clutch/brake pedal and holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch). If your solenoid is a four wire solenoid, check both small wire terminals as one is ground and the other is power from the ignition switch. *If your solenoid is a three wire solenoid, make sure the solenoid body is not corroded where it bolts to the chassis of the mower as this is your ground path back to the battery. *If in doubt, remove the solenoid and clean the mounting area down to bare metal. *If there is no power to the small terminal then your problem is most likely a safety switch, ignition switch or in the wiring.*

Fourth, check for power on the other large terminal of the solenoid while holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch).*

Fifth, check for power at the starter while holding the key in the start position (assistant again).*

Sixth, check your ground circuit back to the battery.

After you have gone through each of the above steps, let us know what happened when you did each step. *At that point we will have great info to tell you how to proceed. *Remember you are our eyes, ears, and fingers, so please be as accurate as possible.

Be as specific as possible with voltage readings as this will help diagnose your problem quicker. *If you do not know how to perform the above checks, just ask and I will try to guide you through it. *Youtube also has some videos and as you know a picture is worth a thousand words.




. . . same thing
 

EngineMan

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  • / Need Help with troubleshooting ignition switch on Murray 12.5 HP
All you need to do is to check to see if you have power on both side's of the switch(s) on orange wire's, if you do not switch maybe bad or not set for start.(open circuit)
I know that they are sometimes difficult to get at, but it's the only way...!
 

MTD

Member
Joined
May 26, 2011
Threads
2
Messages
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  • / Need Help with troubleshooting ignition switch on Murray 12.5 HP
All you need to do is to check to see if you have power on both side's of the switch(s) on orange wire's, if you do not switch maybe bad or not set for start.(open circuit)
I know that they are sometimes difficult to get at, but it's the only way...!


I have full voltage coming in to the switch at pin 2 (red), and I get full voltage coming out of the switch at pin 5 (org) when the key is turned to START.
 

EngineMan

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  • / Need Help with troubleshooting ignition switch on Murray 12.5 HP
That's good, now all you need to do now is to make sure that the contacts of switch(s) clutch/brake and pto are closed so that there is a path for power to go to orange wire on solenoid.
 

MTD

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  • / Need Help with troubleshooting ignition switch on Murray 12.5 HP
That's good, now all you need to do now is to make sure that the contacts of switch(s) clutch/brake and pto are closed so that there is a path for power to go to orange wire on solenoid.


This is what I have been trying to point out - the PTO is OPEN when the blade deck is raised (START position). In order to close the PTO I have to lower the deck and engage the blade. This is what makes no sense to me and I must be missing something. The schematic is correct. I verified this by checked the PTO switch with an ohmmeter - the PTO is open circuit when the deck is raised.
 

EngineMan

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  • / Need Help with troubleshooting ignition switch on Murray 12.5 HP
This is purely for my interest, will it turn over if you lower the deck...?
 
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