Deere STX38 will not start with the key [Solved]

[aceatpool]

STX38, black deck, 12.5 Kohler, Sn # 2415222878, can't find motor #. Batt ref 12.54VDC. Unit will not start with the key. Replaced ign switch with aftermarket switch. Old one checked bad according to service manual. Unit will crank but not start. If the switch is turned to the "off" position quickly the engine will catch & run OK. It dies if the switch is turned to the "on" position so I replaced the aftermarket it with a switch from a JD dealer. Same problem. Jumped brake safety & engine will start if jumped to the solenoid but still not with the key. All the wiring checks good as far as I can tell. Could the new JD switch be faulty? I've had that happen before or am I missing something simple & obvious.

[HondaG100]

To answer the question you are missing something simple. The 2 new keys are telling you the same thing so not likely faulty. Why did you jumper the brake safety? Does it not activate when you step on the brake? Make sure you are installing the wires correctly. By this I mean follow them to their destination using the diagram to make sure no one has messed with the harness before you got it.

[aceatpool]

Thanks for the reply HG. I jumped the brake safety because I was getting the same readings across the terminals engaged or disengaged. The unit still would not start with the new aftermarket switch until I jumped the brake switch. When I did it started/ran fine as per previous. When I remove the jumpers & reattach it to the brake switch it will not start. I'm not a big fan of jumping safeties but sometimes it is necessary. Since I had to remove the motor to work on the bolt holes is there a possibility that I have pinched a wire that will allow it to run but not start? As per previous the machine tried to start with the key prior to my motor repair but not after the motor was reinstalled. Could the wires being reversed on the mower clutch be causing the problem? I have traced the wires from the switch harness to their destinations & get good readings. I have not changed anything in the wiring. I'm not real good at reading schematics but I get by. It is acting like it is missing a ground or is permanently grounded just like when a safety is open. That is why I ended up jumping the brake switch. With the switch in the "start" pos I get 0 VDC at the starter obviously. I can jump from the hot to the solenoid wire in the switch harness & it tries to start so I know that part of the wiring is good. The mystery is why the ign switch will not do the same thing as a jumper??? I know how difficult it is to diagnose from afar as I get calls all the time wanting solutions like my machine is going "clunk, clunk" what is wrong"? My reply is it depends on what your "clunk, clunk" means.................. I do small engine repair as a hobby & don't get paid much for my efforts. I was paid $100 for this repair & I figure I have about 20 hrs in this project so far & it is still not resolved.

[KE4AVB]

What are the part number of the switches you tried and do you have copy of the STX38 black deck wiring diagram that you can post? It and the yellow deck have different switches. I only have a copy of the yellow deck diagram here which is a 6 terminal setup and your switch per IPL a 5 terminal version.

[aceatpool]

Unfortunately I am not able to post a wiring diagram. My TM does not differentiate between yellow/black decks. Only Model number & serial numbers. There is no number on the switch(s) themselves. Only the mfg which is INDAK. The numbers on the JD box is 1(space)AM 119111 and 20140313DY2. All 3 switches (old, aftermarket & new) have 5 terminals. If it had 6 terminals I would have rejected it at the dealer as being the wrong one or at least not matching the old part I removed. I took the old part with me. Learned that lesson many years ago.The new JD switch checks good according to the service manual specifications but the old JD switch does NOT. The aftermarket switch has the ground in a different place which I didn't snap to when I put it on. It wasn't until I got it to run in the "off" pos that I noticed the difference.

[KE4AVB]

Without a valid circuit diagram you will need ohm out the switch terminals in each of the positions and back trace the wiring from each component. It may evenrequire repositioning the ignition switch wires in the connector.

The switch labels I find here are:
M = magento
L = lights
S = start
G = ground
B = battery

Just guessing....
Start position will probably be B + S + L
Run position will probably be B + L
Stop position will probably be M + G
If you have a fuel solenoid then it would connect to L

[aceatpool]

Thanks KE4.
JD does not letter their switches (new or old). The aftermarket does. I do have a circuit diagram I'm just not able to post it here. I have no reason to suspect any problem with the wiring unless I have created the problem somehow. As per previous the crank/start/run was OK until I pulled the motor to do the internal repair. I pulled the starter & the regulator which eliminated all the wiring attached to the motor except for the mower clutch. Had to pull the clutch assy to get to the bottom of the motor and I disconnected those two wires. Put it all back together & this no start problem reared its' head. I did not disconnect any wires to the starter just removed the mounting bolts and set it aside. I never arced anything. I have found no inline fuses or fusible links. It does not have a hydo neutral switch or if it does it is working because it will start & run with the aftermarket switch just like it is supposed to except it only runs in the off pos. If the circuit works with that switch it SHOULD work with the JD switch but it doesn't. I'm opposed to switching wires on the harness. It only creates diagnostic problems for the next guy.

Based on your photo the wiring is as follows to the switch.
G=Black (ground)
L=2 Yellow(mower switch)
B=Red (battery hot)
M=2 White(safeties)
S=Purple (start solenoid)
based on my understanding but the colors I mentioned are correct.

The test in the TM is:
OFF............G & M
RUN............A(L) & B
Start...........A(L) & B & ST
I have no fuel solenoid or working lights on this unit.

In your photo L = A in the manual. All other letters are the same.
Back to the original question? Why will it start & run with the aftermarket switch but not the replacement JD switch? If it were a wiring problem it seems to me that it would not start/run regardless of which switch I installed. Am I missing/overlooking something in that logic??? Sometimes I can't see the forest for looking at the trees!!!

[KE4AVB]

I'm opposed to switching wires on the harness. It only creates diagnostic problems for the next guy.

I agree whole heartily on this as I have had to straighten out no how many makeshift wiring.

And I have seen A and L for the same terminal label by different manufactures.

As for the rest I see no problems with the wiring either here based on your info. I wondering if someone has switch the OEM switch in the box. I have had it to happen to me a couple times @ my local JD dealer. It is the reason I always ohm out a new to me switch before installing. I know you said you test the new OEM switch and it tested okay so I am too at a lost to explain.

I have no fuel solenoid or working lights on this unit.

Understandable but that terminal is use the PTO power too so lights could be added later if someone wanted them.

[aceatpool]

Thanks KE4.
The switch came in an unopened bubble pack but that does not guarantee it is the right part or even functional. Factories make mistakes like we all do. I also have had "new" parts that ended up being faulty that is why I suspected the new OEM replacement even though it checks good according to the TM procedure. I hate to spend another $28 to find out that it is still NOT the problem!!! I'm already out $15 for the aftermarket switch which I was convinced was the problem of it not starting. I want this thing out of my shop..............
I learned a long time ago that diagnosing by replacing parts can get very frustrating not to mention unnecessarily expensive.
It certainly has my head twisted in knots & I'm pretty good at troubleshooting. I reached out to this group because I know there is a lot of school trained, certified techs who have been doing repair for a living for years. I've had several problems solved by the knowledgeable folks on here for which I am
eternally grateful !!! I'm a hobby mechanic & it was/is above my pay grade.

[Luffydog]

is there a safety switch that the pedal hits on under the engine area? also had one in my shop did the same thing as yours. it came in as a service ran good. the guy drove it in and parked it because i was busy and it was at the end of day. next day tried to crank no go just spung over we check all wiring evrything looked good to the eye. so we pulled out the meter same thing all good. so out of frustraiton sitting on the mower thinking and beating my head with a hammer. i slowed down and thought. . then after 4 days of this headache for some reason i pushed the throttle all the way up to choke and guess what it started right up . then i turned it off and guess what same thing would not start. looked at the cable all seemed good. but for what its worth i checked to see if it was firing and it wasnt and didnt until you pushed the choke and throttle cable all the way up. just simple little things cost so much time. anybody else ran into this prob? i failed to look at the carb to see if it was somekind of safety switch that was on the carb b4 it left. just some thoughts and probs i have seen lately.