"Can i run the switch directly off the battery"

Yes you CAN with no problem,however, this bypasses safety features, I'd check connections, broken wires. Does it have an "Interlock" module?

Walt Conner

I have inspected the wires that I can see, but a lot of them pass through the frame. Safety features are nice to have but way, way too many wires. It has a button switch that is engaged by the foot pedal, is this the interlock?
Actually I have already replaced the pull switch and the electric clutch. It ran good through one cut, but the next time I had the low voltage again. I want a simple solution. Thanks.

Everybody wants a simple solution, but sometimes that can't be arranged.
Let me ask you this question, when you are checking the voltage at the PTO clutch circuit, do you have the PTO clutch "disconnected from the wiring harness connector" or are you simply slipping your tester probe into the end of the plastic connector to touch the wire terminal while the clutch is still part of the circuit??
If you are not unplugging the clutch when you test the voltage, you are not getting an accurate showing of whether voltage is actually low, or if the voltage drop is due to excessive current draw by the clutch coil.
I have a Warner clutch manual in PDF format that covers testing and adjusting. If you would like a copy, use the forum e-mail feature and send me an e-mail.

I guess my tired old eyes missed the part about having alread replaced the PTO clutch. So that would seem to eliminate excessive current draw by the clutch itself.
Before you resort to adding any "non-OEM" switches, you need to check the resistance in the wiring from the PTO switch down to the PTO clutch connector with the clutch unplugged. You also need to test the ground side of the PTO connector (on the chassis harness, not the clutch pigtail) to see whether the ground side is sound.
If the stx 38 has a PTO interlock module, it's possible there could be a faulty connection in the wiring, but not having a schematic for stx 38 makes it impossible for me to say for sure.
Normally, PTO interlock circuits only inhibit the electric starter from engaging ifthe PTO switch is engaged (so it will not start if blades are on).
Tractors that have interlock systems featuring "no mow in reverse gear" will have a switch to sense reverse gear and some have a switch to "over-rule" that so you can mow in reverse after setting the over-rule switch. If the stx 38 has this feature, the reverse sensing switch could be faulty, or the over-rule switch itself might be faulty.

Thx for the info. I did test the voltage with the wire disconnected. I read some related threads and decided to hotwire the clutch to see if it is engaging when it gets 12 volts. If that works then i will buy an aftermarket switch. I dont know how to test all the safety modules and they are too expensive for trial and error. Aftermarket is the simple solution. I will let you know what happens. Thanks.

Cory, two points:

1) I suspect that you've got a grounding problem. I suggest that you check resistance through the ground wires.

2) Since you have a meter, you might want to walk through the steps in the link below; it's something that I posted several years ago. It might look complicated, but it's really not.

And BTW, both my STX's do not have interlocks to prevent mowing in reverse - maybe some of the later models did, but my STX manual doesn't indicate it.

Here is a link that might be useful: STX PTO testing

A couple of areas of interest in the wiring harness. 1)Check the other end of the ground cable from the battery. If this is one that attaches via an engine mount bolt especially. Look for the ground wire to the PTO clutch iteself and confirm it is not compromised 2) There is a small red wire coming of the + battery terminal or the solenoid lug where the + battery cable attaches- follow it. Most times there is a spade connector that has issues 3) You will notice a wrapped loom of wires coming from the dashdown above the frame behind the engine. Unwrap and look for brittle, corroded wires. The harness can seem stiff as it deteriorates. Tossing a switch in may seem like a quick solution, but soon enough something else will deteriorate to the point in won't start next.

"Well now pilgrim", if you think you're smart enough to wire up an aftermarket switch..........you ought to believe you're smart enough to follow some instructions and learn to do it the right way.
But you are entitled to your own "philosophy".

LOL you are right pardner, Im looking for shortcuts through this herd of wires. I wish I would have found this place earlier, but Im afraid the neighbors are going to call the lawn police on me. Im going to try hotwiring the clutch, then follow all the good advice here to solve the problem for real.

Well I got the old mare running again. After following all the good advice here, I rechecked my pto leads with the key switch on (engine off) and got a strong 12 volts. After reassembling everything and starting the engine, the clutch was dead and the wire leads were 2 volts again. It seems that the problem is with the key switch. There is a lot of play between start and run on my key switch. With the key in the run position (engine running) I am not getting enough voltage to the clutch. But when I move the key close to the start position, the pto will engage. Well I got the lawn cut, I will do more testing today.

Hang in there Cory, we'll help you whip this thing into submission.

had a similar problem. The engine mount bolt that grounded the PTO black ground wire was loose- causing the pto to work erratically. To see this bolt (13mm I think) you will have to lie on your back and look under the machine. It is above the front steering arm of the right tire. If the wire is dangling you will need a new bolt. Thanks for the previous posts ;)