Safeties in cold weather - safety circuit

[BohoRex]

I have a quick question regarding safeties in sub-freezing weather. I have an OLD snapper LT125 - that I recently upgraded the pulse fuel pump to an electric fuel pump (and it runs SOOO much better now!!)

I typically use this mower as an ATV (with a pull-behind cart) to move equipment and tools across muddy fields - to remove the risk of getting my work truck stuck in those fields. This morning - we were at 13 deg. F. - and I went out to start the mower to put it on my trailer - ran it for 5-10 minutes - and once I released the brake pedal lock, (or eased up on the brake pedal) - the mower would die.

At first I though it was just not warmed up - but after several times of this - I realized it MAY be the safety interlock circuit not allowing it to stay running once the brake was let off. IS there a possibility of one of the interlock switches being frozen in position (either closed or open) and killing the ignition when I try to release the brake? I don't have a spot indoors to warm up the mower to above freezing temps - to see if it just needs to unfreeze a switch.... So was wondering which interlock might be the culprit. (I'll likely jumper the seat switch.... where are the others?)

I DO have a wiring diagram - and on there see the seat switch... what other interlocks are there for me to check? Diagram shows a "Pedal Switch" as well as a
"Reverse Pedal Switch" - are those going to be under the chassis/pedals? If not a switch frozen - maybe a squirrel or rat has chewed a wire or something....

Thanks,
Rex S.

 

[BohoRex]

It's too cold to mess with it today - even though I just went out and warmed up the engine again - and confirmed that yes - it DOES shut down when I let off the brake. I looked under the brake pedal, and saw a wire harness connector there - so I'll investigate later today (after lunch).

As a side note - I can start the engine without sitting on the seat - as long as the brake is set and the blade clutch is not engaged.

 

[BohoRex]

Fixed. On the lower right side of the dash - there's a big green button with a picture of as mower and a forward arrow on it. That button (switch?) is for "Cruise Control" -which- until today - I had no idea was on this old beast. After pulling up the button/switch - it allowed me to move from a braked position to regular transmission control in forward and reverse.

Today's work gets moved to tomorrow....

 

[BohoRex]

I was wrong. Yesterday - at the end of the day - something "happened" to work right, and I got the mower onto my trailer. Got to my client's field this morning (appx 18 deg. F) - and AGAIN - couldn't release the brake again without the engine cutting out. Frustrating - but ya gotta do what ya gotta do.

As a test while it was on the trailer today - I also tried engaging the blade clutch (with brake on). That action ALSO shut down the engine.

- Let off brake - engine shuts off
- Engage blade clutch (with brake engaged/set) - engine shuts off

Can someone walk me through the diagram - or explain what happens in the circuit that shuts down the engine? And provide suggestions of what I should be checking? (like is maybe the seat switch remaining engaged, so it grounds out the coil?) I have found a switch at the brake pedal, as well as over on the throttle pedals.

Of note - maybe - I also recently replaced the ignition key switch. I kept the old one - just in case I needed it - but the key portion was mangled, and I could use literally ANYTHING (like a screwdriver) to start the engine - so I replaced it. As far as I know - it's okay - but I see the purple lines in the diagram going trough it in the wiring harness - so trying to eliminate things that may have been affected when Mercury went retrograde on my mower this week...

 

[StarTech]

I figured you were wrong yesterday. Hint: What safety switch besides the PTO and Brake Switch that is in the grounding circuit for the ignition coil (Magneto)? And pay attention to the note on it too. Also the wire run for chewed wire grounding itself to the frame.

 

[BohoRex]

The only thing coming to mind - is the seat switch circuit. Mine is the 2-wire switch (as shown in the diagram above).... so in theory - if I simply unplug it from the harness - it *should* allow the magneto to not ground out... Just tested that theory - and it still kills the engine when the brake is released.

With switch unplugged from the circuit - the 2 wires in the harness that connect to the switch - have continuity - both at rest with the engine off, as well as with the engine running.

It's supposed to be warmer tomorrow - so I'll get out and see if I can trace the wires through the chassis and see if they're touching or something grounding somewhere.

Any other suggestions?

 

[StarTech]

Nope. Forgetting the automatic shorting strip in the seat switch connector. And I have seen one last that was damage to where it shorted all the time.

 

[BohoRex]

Nope. Forgetting the automatic shorting strip in the seat switch connector. And I have seen one last that was damage to where it shorted all the time.

Thank you - That gives me a good spot to start tomorrow. The connector looks good - I haven't removed the seat, yet to access the button on the seat switch. I didn't realize there was a connector INSIDE the harness connector itself - so that explains a continuity when it's disconnected from the switch.

 

[BohoRex]

Thank you! Took about 5 seconds with a pair of wire-cutters to correct my problem for the day. I'll properly clean out that connector with the spring-loaded conductor inside - later in the week. I bet there's dirt/grass that prevented it from losing connection when it was plugged into the switch under the seat.