I got a little further along on this when I found the old sw. does have some spade markings.

Spade G brown wire goes to ground near the voltage regulator.
Spade S yellow wire goes to safety switches and finally the starter solenoid.
Spade M brown wire to center of 3 wire plug on the engine - blue on eng. side.
Spade L red wire to fuse and voltage regulator.
Spade ? (no mark) red wire with dash tracer goes to amp meter.

These last two red wires might go to the two unidentified spades on the new switch, but, which goes to which?

 

What's the Sears 917.xxxxx number?
Here's a schematic for a 917.25740/41/42.

 

I was hoping you would chime in.

Model 917.25743

 

The red wire with dash tracer is 12V hot. connecting it to one blank spade does make the amp meter bounce but that shouldn't happen with the switch off, right? Touching that same wire to the other blank spade produced some sparking sounds - with the switch off that can't be right either.

I think the assumptions I made thus far based on spade markings are probably in error. Hope I haven't fried something.

I didn't get the mowing done and rain is forecast for tonight and tomorrow.

 

I don't see an "L" in that switch schematic. I guess I may have changed this switch once before.

I was hoping for some clue as to how the two switches differ.

In the diagram "B" and "A" are my choices for the two red wires. I hate when sparks fly and things go tic but I can't quite catch there origin.

 

found this;
http://c.searspartsdirect.com/lis_png/PLDM/00010160-00006.png

Or if that doesn't work try this;

 

Battery
Ground
Magneto
Solenoid
L/A lights/Accessory
Note- Usually a switch with an Rectifier terminal would do this.

Battery typically connects to LARGE terminal on the starter solenoid that the + battery cable connects to.

Ground- Self explanatory.

Magneto is grounded when key is OFF only.Connects to engine kill wire.

Solenoid switched to B in the Start position ONLY to energize starter solenoid.

L/A Connects to rectifier output. Is switched to B in the RUN position only.

 

Thanks Bill, hopefully in the light of day all will gel as it should. I've gone around in circles on this issue too much today and will call it quits until tomorrow.

I see now a circuit breaker present which probably explains the tic noise.

Thanks again, Steve

 

My problem continues.

What I've learned.

The new switch is a 4 position switch. OFF ON ON START
This helps explain why the amp meter needle jumped and some sparks and noises while hooking up the wires, the switch was in the first ON position (not OFF). Seemed logical at the time, twist the key to start detent then back thru ON to OFF.

Looking at the back of the switch (see sketch with spade identification), I wired it up after finding that B and S were connected in the start position only. G, M ans S were already identified on the spades. The wire at B is at 12 Volts and goes back to the battery - no other connections. The wire at A goes thru an inline 20 amp fuse and on to the rectifier block plug.

All wired, battery hooked up, I find the amp meter shows discharge of 30 Amps in the first ON position. I quickly pass on to the second ON position and all seems okay, no discharge indicated. Move to the start and see a slight needle discharge but no started motion.

I wondered why the big discharge in the first ON position. I know now that B goes to G with the switch in the first ON position. I can tell you it doesn't take long before smoke is rolling off the switch and it keeps on smoldering long after the power is disconnected.

What next????????????

 

2 ON positions on a 5 tab switch doesn't make sense.
Typically, that type switch would have-
OFF
Run with lights
Run
Start.
Get the correct switch. Even if it has the correct number of terminals, it doesn't mean it's wired the same internally.

 

Get the correct switch. Even if it has the correct number of terminals, it doesn't mean it's wired the same internally.

I hear you Bill and I will be getting the correct switch but it will take some time to accomplish that. I hate to admit I had't noticed it being a 4 position switch. I bought six of these from the seller "sell-lo" on ebay a few years ago. They were supposed to be for Sears Suburban that's all I remember now. I must have used one or maybe gave it to someone because I only have 5 (make that 4 now, after the smoke) left.

Another question. This is a magneto engine so if I pull the 3 wire connector to the engine and jump start it directly on the starter post and ground it will run, right? It doesn't need a battery to run. I could provide a wire and ON OFF switch to the center pin position at the engine 3 prong connector routed to ground to stop the engine (ground the mag out). If I'm right about this I could mow my lawn using this technique until the new switch arrives. I also noticed that the inline 20 amp fuse connector that goes to the voltage regulator/rectifier block got fried using this wrong switch - I will replace that also when I change out the switch.

Does this sound like a workable plan? Yes I will pay particular attention to the safeties - neutral start and pto disengaged during startup. Thanks, Steve

 

btw, searching the 31 2941 number on the switches I have brings up lots of hits, here is one.

31-2941 - Roper/Sears 73232 Ign. Switch (Magneto) Replaces Roper/Sears 14615, 73232. (Magneto) Replaces OEM #: 73232. Suggested Retail Price: $25.79

Another;
31-2941 - Roper/Sears 73232 Ign. Switch (Magneto) | Lawn Mower Parts | MFG Supply

From the manual at Sears;
Sears Parts Direct has the correct switch listed for on-line purchase ~ $23.

Switch Part #: 3492R
Substitution: 583732501

 

Why would search for the part# you have, when it's wrong?

Search for-
AYP 3492R switch

If you get the engine started, you don't need the battery to mow.
You could probably engage the blades on idle to kill the engine.

Just jump 12V to the small solenoid terminal to start.

 

Why would search for the part# you have, when it's wrong?.

I guess I'm trying to justify my purchase. I remember asking the seller if these switches would work in an Sears ST/16 garden tractor, I was told yes. We know different now. I thought that maybe a pinout would be available for the part number to help me understand the switches operation/use. I doesn't work for this application but maybe it would work in another situation so I wouldn't be left holding onto/junking the leftovers.

 

GT_80 had posted a while back he found a direct switch replacement through NAPA, I would have to search is threads to find it.


Here is the back of my ST16 switch for spade placement


Just make sure the Mag wire only goes to mag spade on switch, that's your biggy.

You have these correct, I edited the last one

Spade G brown wire goes to ground near the voltage regulator.
Spade S yellow wire goes to safety switches and finally the starter solenoid.
Spade M brown wire to center of 3 wire plug on the engine - blue on eng. side.
Spade L red wire to fuse and voltage regulator.
Spade ? (no mark) red wire with dash tracer goes to amp meter. goes to B terminal on switch

 

Found it.....



Part Number: SME 701850

Product Line: NAPA Small Engine







Attributes:

Power Equipment Manufacturer : Economy, MTD, Murray, Noma, Roper, Toro/Wheelhorse

# Switch Terminals : 5 Spade Term

Contents : Ignition Switch

Fits Power Equipment Model # : Most L & G Tractors w/ Magnetos

Replaces OE Part # : 03-2028, MTD 725-0267, 925-0267, Murray 21064, Noma 44745, 300295, Roper 3621R, 4406R, Toro/Wheelhorse

 

Found it.....


Part Number: SME 701850

Product Line: NAPA Small Engine

As I said already, I plan to use the switch called for in the manual for my ST/16 Model 917.25743 and that is a;

From the manual at Sears;
Sears Parts Direct has the correct switch listed for on-line purchase ~ $23.

Switch Part #: 3492R
Substitution: 583732501


Thanks anyway. The lawn is mowed and I await parts for the necessary repairs.