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Sears Craftsman Won't Start! Funky Switch Circuit Diagram

6625 Views 5 Replies 3 Participants Last post by  Whirly
My Sears Craftmans Riding Mower Won't Start!!!

It's a 12.5 HP 42" Riding Lawn Tractor Model 917.2555.81. I don't know the year. (old!)
Originally the Power Terminal from the Starter Relay on the Starter cracked and was shorting.
Took the Starter apart and repaired it with Gorilla Epoxy and Electrical Tape. Yeah! The Starter
works when connected to a battery when mounted on the engine! But there still seems to be some problem with the Starter Switch, or the Starter Relay/Solenoid.
Both of the parts are available from Sears Parts Online. But I don't want to order the parts untill I've
definitively proved which parts is bad, and probably gotten the mower to start by bypassing it.

I found a circuit diagram for the mower at:


which is great... I will probably bypass all the safety interlocks to make it easy to diagnose...

The question I have is about terminal M on the Ignition Switch. It appears to be connecting to ground
under various conditions: (Seat Switch Not Occupied), (Attachment Clutch Off), (Key Switch Off).
This puzzles me because it apparently connects the ignition module to ground when (Key Switch Off)
or ((Seat Switch Not Occupied) and (Attachment Clutch On)). Which makes sense as far as that goes,
but what about when ((Seat Switch Occupied) and (Attachment Clutch On)), or (Seat Switch Not Occupied) and (Attachment Clutch Off))? You want the mower to not start in all these conditions, and
only start when (Key Switch On) and (Seat Switch Occupied) and (Attachment Clutch Off)!

If the wiring is actually wired this why, I don't see it resulting in the desired Behavior; only starting when the last set of conditions are true.

The other issue is that I don't see anything other then Black/Ground being connected to the Ignition
module and spark plug; it seems to me like there needs to be a connection to power somewhere
there!!! I would think that Terminal M should connect the Ignition Module to Power at least during the
right starting conditions!!! But that's not what the circuit diagram seems to say!!!

Also the Ignition Switch Table doesn't seem to say anything about turning on Terminal M to the
Ignition Module when the Key Switch is in the On or Start positions. It seems to just say that it isn't
Grounded when ((Key Switch (On or Start)) Or (Seat Switch Occupied) Or (Attachment Clutch Off)).

This implies that I should be able to get this to run merely by clipping the Black wire on Terminal M
to the (Attachment Clutch Switch) and (Seat Switch). This leaves the Ignition Module Grounded only
when the Key Switch is Off; Which sounds like usefull behavior.

Am I reading this Right??? I'll try it tomorrow!

Thanks, Jaimes Beam, Franklin ME
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...I found a circuit diagram for the mower at:

Link seems to be broken. :(
Here's the circuit diagram...

Here's the Circuit Diagram at:

The forum SW seems to have garbled the URL.

I had also tried to attach it to the post, but I guess it's too big.

Jaimes Beam
the black wire from the ignition module does NOT need a power just grounds out the module & kills the spark....thus stoppin the engine or not lettin it fire up....theblack wire is grounded at the ingition when key is in OFF poaition....when one of the saftey switches is faulted out driver off seat....this grounds out the black wire...& kills engine or will not let it start...
if starter does not turn over when clutch/brake pedel is down & the attackment... clutch is disengaged... the solenoid is prolly test it....remove the white wire off it & run a test jumper from the positive post of battery to treminal u took white wire off....if this doen not turn over the engine....install a diff solenoid.... ****** note....(not all solenoids r made the same.....some r a grounded type & some r a ungrounded type 2 wire (both small) AND all will have 2 big post type for starter) this wiring diagram indictates to me this is a grounded ...(one wire) type
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