I have a 25HP 2003 model Sears tractor that dies each time I either release the clutch or turn on the mower PTO. I have replaced the plunger switch under the seat but that didn't solve the problem.

There is a similar switch on the linkage for the clutch. The one you replaced keeps you from getting off the tractor while the blade is engaged. You were on the right track.

My mower is not a Sears but the condition you suggest occurs on my MTD

When you try to go in reverse - while the mower blade is engaged...

A Switch by shifter and switch on the mower engaging lever kill engine

The one on the seat kills engine when you get up off seat...

I would say to call Sear's --- They can probably help but it usually takes

A long time on phone to talk to them...

Biggsie, that was a very unpopular safety feature MTD tried, can't go in reverse with the blade engaged. I think they have dropped that feature since it caused a lot of complaints and people bypassing the safety switch.

Ball is correct on the aggravation part of the reverse kill switch. I mean you purchase a unit with the hydrostatic transmission that is operated by your foot and mow forward, then pull up close to something, mash the back of the pedal and it dies. Many of these have been bypassed. That is something we do not do except for diagnostics and will not even tell someone how to do it themselves. That keeps it safer for us.

Actually I think we have Iremin headed in the right direction but here is an inetresting note. I just took delivery of a LT2000 Sears tractor that has an option on the ignition switch called ROS (reverse operation switch). If you just start the tractor and leave the key in the on position it will kill if you put it in reverse with the blade engaged. If you leave the key in the ROS spot it keeps running with the blade engaged and in reverse. I only tell you this because it is new to me and may affect how we answer questions in the future.