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A friend has a STX38, the electric PTO clutch burned up on it and the engine would not even turn over. I removed the pto clutch and found it to be wasted. He bought one on Ebay that was said to be good. I installed it yesterday and now the motor won't do anything not even a click from the starter relay. Is there a way to check the PTO clutch to see if it is servicable? Or could I simply jump the two wires that connect to it and see if the motor will turn over? At first I thought it was a bad battery so I charged it and still nothing from the engine or relay, I then tried to jump start the mower and nothing. I could really use some help on this one as I am stumped.

12 volts to the PTO to see if it engages.

Most likely you have burned out the fuse or fusable link ( light duty wire ) or the power relay.
I don't have service information for that mower.

However power to the ignition switch generally comes from the batery terminal on the solenoid then to the PTO switch then to the PTO clutch.
You can check the clutch bu connecting it directly to the battery.
Run a light jumper from the battey + wire to one of the trigger terminals on the starter solenoid and another from earth to the other control terminal.
Motor turns , you have an electrical problem

I checked for a fuse or fusible link and found nothing. Ran a jumper wire to the starter and it turned the motor over. Jumped the starter relay and got nothing. Checked voltage to the starter relay, it's good. Getting nothing coming out of the other side with the key in the start position. I'm waiting on a phone call right now, then I will hook power directly to the PTO clutch and post the findings. I am thinking the starter relay might be burned up.

You can check the relay, or swap it with one of the seat switch relays as they do not stop the engine cranking ( earth magneto ).
You can make a short jumper with 2 male 4.5mm spade terminals and plug it into the relay socket.
This makes that circuit permanantly closed.
I do it all the time when doing a diagnosis .
Please do not use the mower in this state

tim2 said:

I checked for a fuse or fusible link and found nothing. Ran a jumper wire to the starter and it turned the motor over. Jumped the starter relay and got nothing. Checked voltage to the starter relay, it's good. Getting nothing coming out of the other side with the key in the start position. I'm waiting on a phone call right now, then I will hook power directly to the PTO clutch and post the findings. I am thinking the starter relay might be burned up.

Click to expand...

Starter relay or starter solenoid ?
Starter solenoid should be a 4 pole type and the safetys work on both the + & - sides of the relay control

Sorry just corrected my errors on the last post. I am thinking the solenoid burned up when he kept trying to start the mower with the bad pto clutch.

I checked for a fuse or fusible link and found nothing. Ran a jumper wire to the starter and it turned the motor over. Jumped the solenoid got nothing. Checked voltage to the solenoid, it's good. Getting nothing coming out of the other side with the key in the start position. I'm waiting on a phone call right now, then I will hook power directly to the PTO clutch and post the findings. I am thinking the solenoid might be burned up. Tried testing the solenoid and have no power coming out of it to the starter.

Ok, I am out of ideas. I replaced the solenoid and still have nothing for power going to the starter. Hopefully someone else has another idea on what to check and how to approach this Deere.

tim2 said:

I checked for a fuse or fusible link and found nothing. Ran a jumper wire to the starter and it turned the motor over. Jumped the solenoid got nothing. Checked voltage to the solenoid, it's good. Getting nothing coming out of the other side with the key in the start position. I'm waiting on a phone call right now, then I will hook power directly to the PTO clutch and post the findings. I am thinking the solenoid might be burned up. Tried testing the solenoid and have no power coming out of it to the starter.

Click to expand...

Jumped the solenoid ?
How, which wires to what ?
We can not see what is happening.
The solenoid should have 4 terminals
2 big ones for the power and 2 small ones for the trigger
One small one needs + and the other needs - to make the solenoid energise
I think on your mower the + is blue & the - is black.

Usually there is a thin wire also connected to the big terminal with the wire from the battery that takes power up to the B (battery ) terminal on the ignition switch.
When you turn the switch to the Start cosition, the switch bridges the B ( battery + 12V ) to the S ( Starter or solenoid if you like ) terminal
From there it goes to the PTO switch then to the hand brake switch and finally down to the solenoid control + wire, generally dark blue on Deeres
The other control wire on the solenoid goes through the seat switch relays, ignition relay and sometimes a few others before it gets to the black control wire on the solenoid or - if you like.

Some where before th 12V + gets to the key switch there is some sort of a fuse.
You might like to get the voltmeter or teat lamp and confirm you have voltage to the ignition ( key ) switch cause if you aint got power there nothing is going to happen and you can replace the entire starting system 10 times over , it will not go.
The power feed to the clutch will either come through the same key switch or go through a relay energised by power from the key switch which then goes through the PTO switch.

Yes I have jumped the solenoid, two large posts and got nothing. There is no power cgoing to the side of the solenoid that is wired to the starter. Yesterday I replaced the solenoid with a new one and got nothing when I tried to start the mower, then I replaced the key switch still nothing. I then jumped the seat and brake safety switches and again no power to the starter. I checked every wire for a fusible link or a fuse and have found none at all.
I am going to test to see if the key switch is getting power today, hopefully it is as it was working (cutting grass) about a week ago. If I find the key to have power CAN I unhook and jump the two wires going to the PTO Clutch and try to start the mower? Or will this damage the pto clutch.

So you bridged the two large terminals and the starter did not turn.
OK, Now we are getting somewhere as we are understanding each other.
To test the solenoid, dissconnect the two control wires. Run power to one and earth out the other,
You should get a loud click.
If that is the case run your heavy jumper to the starter terminal post on the solenoid.
Motor turns = starter feed wire is OK motor does not turn, lead is faulty.
Move the heavy jumper to the battery side of the solenoid and use the small jumpers to energise the solenoid as per before.
Starter turns = solenoid OK and the main power wire from the battery to the solenoid is faulty.
Leave the heavy jumper on the battery side terminal, reconnect the two control wires to the solenoid and try the key.
Starter turns = wiring & safetys are OK
Starter doesn not turn = another problem in the wiring.
Naturally brake on PTO off.

OKay I think I understand whate you are saying. The two control wires you refer to are the small wires on the bottom of the solenoid correct? It really has my mind spinning because the owner was cutting grass when the old PTO clutch burned up. Seems to me that it is the new clutch that is faulty and not making connection when I attempt to start the mower. Going to follow your last two post and once done I will connect 12v dirrectly to the clutch to see if if functions at all. Thanks for hanging in there with me. I will post results once the sun comes over the horizon.

Bert, I just tested to see if there is power at the key switch, and yes there is power going to the switch. I then removed the two small wires on the solenoid and ran jumper wires to the terminals, one ground and one power. I did not get a loud click the motor actually turned over. I checked continuity of the positive wire from the battery to the solenoid and it gave a reading of 0.03 ohms which tells me it is okay. I then plugged the small purple wire back onto the solenoid and left the other hooked to a ground, reinstalled the key switch and got no noise from either the solenoid or the starter.

I just thought of something else to test. The old PTO was liquid welded back togetrher and when it broke if locked the motor to the point it could not be turned over with an imp-act gun. What is the possiblity that it also burned one of the electrical wires running to it? HMMMMMM might have to get out the multimeter again.

Continuity tested great. Back to square one, haven't anthing that is keeping it from turning over..........

haven't read all the post just jumping in. Please excuse me for just jumping in but you may want to check the PTO switch with an ohm meter and make sure the contacts open and close. I have had the pto clutch to go and it takes the pto switch with it.

I tested the PTO switch and it is good. The mower was running when the old PTO clutch went out.

Again for the purpose of clarity.
The control wires are purple and black.
If this is the case you should see 12V at the purple wire when you turn the key switch to start.
You should also get continuity to earth on the black wire when you turn the key switch to start.
If no 12V follow the purple wire back .
It should go to the brake switch then to the PTO switch then to the key switch.
Generally it changes colour at every switch just to confuse you.

If the black wire has no continuity to earth then you are looking at one of the relays

I poked around for a little while on it yesterday and came up with nothing new. I will check your last tip today, I have an appointment this morning so it will be later today. I have not seen any signs of relays, it appears everything is just straight wired with no relays, fuses or fusible links. Anyone have a wiring diagram for this STX38 or ideas where the relays and fusible links are?
Bert, the purple wire from the solenoid goes directly to the PTO clutch and the other wire goes back to the PTO switch. I will post back what I find today.

tim2 said:

I tested the PTO switch and it is good. The mower was running when the old PTO clutch went out.

Click to expand...

How did you test the PTO switch? What is the engine model number?

To test the switch I loaded themower and took it to a repair shop and had them test it. The engine model number is CV13S. I really need to know where the realays and fusabily links, and fuses might be.

tim2 said:

I poked around for a little while on it yesterday and came up with nothing new. I will check your last tip today, I have an appointment this morning so it will be later today. I have not seen any signs of relays, it appears everything is just straight wired with no relays, fuses or fusible links. Anyone have a wiring diagram for this STX38 or ideas where the relays and fusible links are?
Bert, the purple wire from the solenoid goes directly to the PTO clutch and the other wire goes back to the PTO switch. I will post back what I find today.

Click to expand...

No it does not not.
It should go to a safety switch and that is usually the brake as that in under the mower just near the solenoid.
From there to the PTO switch and from there to the key switch.

The starter solenoid is not connected to the clutch or the engine would crank whenever you turned the blades on.


The PTO clutch wires are Blue + 12V and black ( earth )

Try unplugging the lighting circuit from the PTO switch and then report back.

Okay, I chased these wires yesterday and this is what ids on this mower. The purple wire leaves the solenoid and goes to the PTO clutch, there is a black wire leaving the PTO and it goes to the switch to engage the blades. That is how it was wired when the guy pushed it up my driveway. There is no wiring from the PTO to the lighting system. I have NOT FOUND a relay, fuse or fusible link yet. I am at a total loss with this no power to the starter.

Well no wonder it did not go.

There should be a blue wire and a black wire that goes from the PTO switch to the clutch.
Where they go through the mower floor there should be 2 wire plug so you can change the clutch.

The starter solenoid and the PTO clutch can not be on the same circuit because they are mutually exclusive.
You can not start the mower with the blades engagd and the blades can not engage while you are starting the mower.

Now this is going to be a PIB type job but as some one has been in there making a mess out of things you now have to set it right.

Nice thing about JD is their wiring colour scheme is farily well consistant.
We will start everything from the key ( start ) switch because this will keep things simple as possible.
Remove the plate with the start switch & pto switch on it, it should have enough cable to pull up clear of the fender.
Flip it over and test for 12 V at the red wire and ground on the black wire.
If you do not have 12V at the red wire , nothing will work
Look closely at the back of the switch you will see the following
G - Ground wire,Black direct contact to ground
M - Magneto kill wire , White can be single double or tripple , connects to the magneto and the safety cut out switches. Kills the spart to turn off the engine , connects to the black wire with the ignition off.
B - Battery wire, Red, 12V connects to the + on the battery or the battery lead on the solenoid. This wire should have the fuse on it.
A - Accesory ( run) wire, Yellow , goes to the carb solenoid ( if you have one ) and the light switch ( if you have one )
S - Start wire , purple, usually goes to the PTO switch and becomes purple + white ( or + yellow ) then goes to the brake or neutral switch and becomes full purple again hence on to the starter solenoid.

Connections go like this
OFF G + M
ON B + A
START B + A + S

So check the ignition switch and report back
If your brain is not fried you can try tracing the purple wire. It may got to a few other things and usually will change colour every time it goes through a switch so purple + white, purple + yellow , purple + black etc etc etc.
Even worse it can go purple then purple + trace then revert to purple then purple + trace so just because a purple goes in and a purple come out it does not mean it has not been through a few switches.

Well I have not fried my brain. I checked the switch as suggested and everything checks out. I am still baffled by the purple wire going from the solenoid to the PTO Clutch. When I started trouble shooting the mower you could here the solenoid click every time you turned the key but the motor would not turn over. I pulled the spark plug and tried the key again, solenoid clicked and motor did not turn over. I removed the plastic cover on top of the motor and tried to turn it over first by han then with a wrench and could not move it. I then looked underneath and found the PTO clutch burned out. I removed the clutch, both wires in one plastic housing(one wire is purple). Installed the new clutch plugged the wires into it. Turn the key and nothing at all not eventhe clicking noise from the solenoid. It looks like it is going to need to be taken to a shop. I would really like to see a wiring diagram for this model engine CV13S. Hopefully someone has it and can post a copy of it or a link to one.

I thatnkyou for the diagrams. Now does the guy want to pay $200 for a new wiring harness or not?

I can't stop trying to figure this thing out. I just replaced a whole bunch of the wiring and got fed up with it. I have a couple ore to replace and then to test two wires for continuity. I have little faith that this work is going to correct the no power to the starter but I will keep you posted. He does not want to purchase a new wiring harness.

Now we have a wiring diagram things will get a bit more simple.

Check the entire power ( purple wires ) feed to the starter solenoid. Forget about the clutch for now, one thing at a time.
Pull the plug off the back of the starter switch and connect 12V to the purple wire in the key switch plug.
I like to use a test lamp rather than a meter but it dosent really matter.
Follow the 12 V through the PTO switch and then all the way to the starter solenoid.

Some where along the line you will find the black hole to the parallel universe where 12 V goes in and nothing comes out.
By probing for your 12 V signal you won't have rip all the loom open to find where the wires actually go.

Do one circuit at a time, forget about what was there that did not make any sense.
People with no idea what they are doing shove wires all over the place bypssing this and cross wiring that willy nilly.

When I started out I got into the same trap you are in trying to figure out what I was seeing in front of me rather that checking and repairing what should be there.
One circuit at a time and all of a sudden you will see wires that are not supposed to be there or hooked up to the wrong place.

So once you get the starter wire sorted out then go to the PTO clutch wires.
They are easy as they go directly from the PTO switch to the clutch.

I Well I thought I got the wiring figured out until yesterday. I tested the PTO switch and it was bad, bought a replacement and gave it a shot. The ignition switch did nothing when turned, but I can now jump the solenoid and make the engine turn over. I will test the ignition switch today and see if it is good or burned up also. Will post results this afternoon.

Ignition switch was bad, bought a replacement and no change at all. It still does nothing when I turn the key. HELPPPPPPPPPP.

I'm just curious, with all this testing , have you checked the battery voltage...??? are the battery cables CLEAN & TIGHT ?? Is the start solenoid properly grounded ( clean & tight connections ) SOMETIMES we overlook the most obvious. .... Boobala

The battery is brand new all the cables have been cleaned and are tight everything at thee solenoid is correct. I think when the PTO clutch burned up it took a bunch or wiring and the ingnition and PTO switch with it.

Yesterday I replaced th PTO switch Ignition switch and found the seat safety switch to be bad. I can now jump the solenoid with a screwdriver and the motor will turn over, getting nothing when turning the ignition switch. I also checked continuity on some of the wiring and found none to be burned up.

OK,
You have a circuit diagram.
Read it.
Seat switch is not in the starting circuit. It is in the magneto cut out circuits.
Depending upon which model you have the starting circuit has 4 or 5 switches
1) ignition switch
2) Pto switch
3) Gearbox neutral switch
4) brake switch
5) solenoid.
Do as advised.
Pull the ignition switch plug and put 12 V into the purple S wire on the switch plug and follow it through the machine.
Stop fantasy thinking.
Look, then do
One circuit at a time.
IF IT DOES NOT CRANK THEN THE PROBLEM IS IN THE CRANKING CIRCUIT