Small Engines (Lawn Mowers, etc.)/Riding Mower


QUESTION: Hi,  I have a 2005 troy bilt riding mower.  Body type number is 13AN779G766.  The engine is a 17.5hp Briggs & Stratton,  Model 31C707, Type 0154-E1, code 0508227E.  Recently, my wiring harness somehow got caught in a pully and it tore it up completely.  I bought a new solenoid switch and carried the mower to a nearby mower shop to have it straight wired.  A week later I went to check on it and they had put on the solenoid switch and a new key switch and attempted to straight wire the mower.  They failed.  They had burned up the coil and said they replaced it and said they did not know how to straight wire the mower.  I am hoping you can help me straight wire it.  When I bought the mower all the safety switches had already been removed or disabled.  I had the engine rebuilt a year ago and it runs and cuts really good.  Here is a YouTube video, where a guy straight wires his lawn tractor.  Will you see if this will work on my mower please?  I don't understand how he runs a wire to the battery end of the solenoid switch without the battery draining down when not in use. .  I'm afraid to try and use the key switch they installed.  It has 4 or 5 prongs on it.  I think I would be better off using the toggle switches like on the video.  I know how to run a kill wire from the coil to ground to kill the engine.  It's the other stuff I'm not sure of.   If you can help me, I will greatly appreciate it.

Stephen Pettyjohn

ANSWER: Pull your key switch off the mower and look at the back of to see what letters are there.  Send me the info and we can get started.

A close of pic of the switch will also help.  Just attached the pic.


---------- FOLLOW-UP ----------

QUESTION: Hi Eric,  I'm sorry for being so late in replying, but the weather here has been rough.  I have the information you requested concerning the key switch.  I'll try to explain it the best I can.  The back of the switch has 5 connectors.  One has a G, one has a B, one has a W or M depending how you look at it.  One has a S and one has a 7 or a L.  I hope this helps and you can understand it.  A friend and myself removed the wiring from the back of the mower up to a place where we couldn't get to it anymore, so we cut the wires there.  We also removed the solenoid switch and plan to put it in a more accessible place.  This key switch is not the one that came on the mower.  It was installed by the mower shop I told you about.  Hopefully we can get by with just bare bones wiring.  Thanks again for your help.


ANSWER: G = Ground, can run straight to the batter or any metal frame connection.
B = Battery, run straight to the battery but use and inline 20 amp FUSE to protect the circuit.

M = magneto, this goes to the engine shut-off connection.  You can follow the wire from the igntion coil to the connection on the engine block.  Connect M to this connection.

S = Solenoid/Start.  This goes to the small post/terminal on the starter solenoid.

L = Lights

All that's left is the charging system.

Check out this reference:

Page 21, which switch do you have, Briggs or Brand X?

Do you have a voltmeter/multimeter to measure 12 volts DC?


---------- FOLLOW-UP ----------

QUESTION: Hi Eric,  Here is a part number for the original switch on the mower; troy-bilt 725-04227.  At the local parts store they want $75.00.  I found an Oregon brand that says it is a 7 terminal and 4 positions at for $14.07 that has a picture that looks like the orginal.  I  guess this would be a brand X.  Also, I do have an analog multimeter.  The weather is predicted to be heavey rain through tomorrow.  I will pull off the original switch when the weather clears and inspect it. Here is a link to the picture at   Thanks again,


This link may have some different options:

Another good link:

The letters on the back of an ignition switch stand for the following:
M = Magneto
S = Starter Solenoid
L = Lights
A = Accessory
B = Battery
G = Ground
I = Ignition
R = Regulator/Rectifier

The designated terminal connects in some manner to that component. For example, the B terminal connects in some manner to the positive battery cable.

You can buy a 5 pole harness here:

I did not see an electric PTO on your mower. Most mowers without an electric PTO clutch use the 5 pin switch.  You will probably have a anti-afterfire solenoid on your carb.  You can use the 5 pin or 6 pin switch as long as you have 12 volts going to the solenoid when the key is in the RUN position.  The light or accessory should be able to supply the power for the anti-afterfire solenoid.

7 pin connector link: Connectors &b=Universal&id=946

If I was doing the job I would get the universal 7 pole switch, connector, and terminals.  I would check the switch with my meter for continuity in each position to verify the switch connections.  I'd write down what was connects to each pin after verifying the switch positions.  Then I would start building the harness.  Once built I would only connect the battery wire on the switch and then check for 12 volts DC on each wire to verify NO power is going to the M terminal.  When you turn the key off the M wire should short to ground or the G on the switch.  If you send 12 volts to the engine ignition coil module you will destroy the module.  

Verify 12 volts on the wire that connects to the anti-afterfire solenoid when the key is in the START and RUN position.

Finally, I would tackle the charging system.  How you wire the charging system depends on which switch you use.

Mower wiring is not really that difficult if you have a basic understanding of electronics and know which components need power, when they need power, and which components DO NOT need power.

Let me know it this helps.

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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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