Could you please get the Ariens model number and serial number from thge data decal on the machine.
Need both to view the owners manual/service manual to see a wiring diagram.
Of course you can wire direct from a 12V source and even add a switch if that is what you are determined to do.
BUT......why not try to find the cause of the problem in the existing electrical wiring before you go Frankenstein?
Refer to the photo below. It is wire damage found in the PTO clutch circuit of a Gravely ZT 1232 (which has an Ariens "counterpart" in their line-up) owned by another member of this forum. A new PTO switch would not have helped with this damage shown here, but this was not the worst of the man's problems. His PTO clutch had also disintegrated. But, the owner was able to repair, or circumvent the damaged shown by "wiring around" this plastic connector.

Your Ariens might have a similar connector with similar damage/high resistance that is preventing the PTO clutch from engaging with the OEM circuit and a new switch. If you want to check, you can run a new wire from the PTO switch down the the PTO clutch pigtail and see if the PTO engages dependably with a new run of wire. If it improves performance, you surely have some damage somewhere in the OEM wiring, possibly like the damage had by the other member.
Model and serial numbers please.

{{gwi:350139}}

Thanks a lot for your help!
model # 915077
serial # 020154
Ariens 1840 ZT IZT hydros, Kohler 18 HP engine

I was able to mow my entire lawn today with it taking only 10 pulls for the PTO switch to final start the blades. I'll check that clip in the morning. I spent about 10 hours this week in a hot garage poking around trying to find something. My ability to solve electrical problems is pretty limited. Thanks again!

Just 10 pulls, that's almost as good as a new mower!
I have the wiring diagram now. Will peruse it carefully. I already see that the PTO switch on this model does not carry the load of the PTO clutch. On this model, the PTO switch is only a "messenger" to operate the PTO relay, which does carry the electrical load of the PTO clutch.
I'll get back with more info after I have chewed on this diagram a bit.

I got lucky with only 10 pulls. Other times I haven't been able to mow my lawn after 30 minutes of trying to get the blades started. Thanks again - I'll got look at the clip.

Another bit of info - this winter I used the mower as a plow. It worked like a champ but got wet as it was snowing hard when I was plowing. I should have covered up some of the electrical areas with a plastic bag or something. Do you think that contributed to this problems (educated guess?).

I looked at the clip. All the prongs look like new. There are no signs of damage on either side of the clip after opening it up.

OK, I figured that would probably be the case after learning the electrical load of the clutch is borne by the PTO relay on this model of mower.
Find the component I have labled "RELAY" in the image below.
Your mower has three relays like this one.
Look on your mower and find the relay which has the following color wiring in the connector the relay plugs into. There will be a "GREEN with WHITE stripe" wire, a "BLACK with WHITE stripe" wire, a "PURPLE" wire, and a "PURPLE with WHITE stripe" wire.
Unplug this relay and inspect the wire terminals of the connector for signs of corrosion (green or white powdery appearance) or overheating (a blackened, blistered look and maybe some melting or distortion of the plastic connector body).
Inspect the male spade terminals of the relay for identical damage of both kinds.
I would suspect overheat damage (if any) to be on the PURPLE and PURPLE w/ WHITE stripe wire terminals and spades.
Corrosion damage might be found on any/all terminals and spades.
Post back what you find.

{{gwi:350140}}
{{gwi:350141}}

I found the 3 relays under the panel where the ignition switch is located. I inspected the relay you noted and found no visible sign of any damage. I inspected the other 2 relays and there was no sign of damamge. No corrosion at all - I keep the mower in my garage. I can try to clean them but they look like new.

That wiring diagram is very helpful. I wish I knew more about this mower. I didn't even know where the relays were located.

Should I try jumping something with a wire to isolate the problem???

Since you unplugged the relays and plugged them back in again, is the PTO clutch still not wanting to engage? Sometimes, it requires only unplugging and plugging in the relay to restore continiuty to the circuit. I'm more in favor of checking for 12 volts at some strategic locations than jumping with a hot wire.
I'll post some steps later this evening, got something else going on right now.

It still won't engage. I did jump a wire from the battery to the purple wire with the white stripe at the relay and it clicked the clutch. But that was kind of what I had already done just much further down on the clutch harness.

I gues the relay could be not working with no external damage?

I'm still willing to go Frankenstein.

Thanks again!

You can probably swap the relays to see if the problem manifests itself differently?????

It was dark out and I'm out of gas (go figure) but I swapped the relays (PTO/Starter Solenoid relay) and I heard the clutch click. I tried it several times and before the swap the clutch did not click! I also tried to start the mower and it cranked (but with no gas it wouldn't start). I'll buy more gas in the morning. What a great day! Thanks for all the help. I'll let you know what I find out. Should something else not work?

Yes indeed, what a day. The image below shows what you should have in "hot wires" and when for terminals 30, 86, and 87.

Terminal 85 is the ground circuit for the PTO relay.
Terminal 85 must be checked with one lead of the volt meter attached to a "battery positive" source and the other test lead touching the 85 terminal.
Terminal 85 should show a "ground" under the following conditions: (1) Key ON, and seat occupied. (2) Key ON, PTO switch ON, steering controls at NEUTRAL, seat empty.

The relay Ariens has labeled "START RELAY" really should be called "RUN RELAY" because the only thing it does in regard to "start" is remove the magneto kill wire from being grounded. When the magneto wire loses its ground, the ground is moved to 87 of the start relay which grounds terminal 85 of the PTO relay.

I see that you have swapped relay positions and can now hear the PTO clutch click to engage. Bravo Bill Kapaun! I hope your eyes are doing great. It sure seems they are.

nycjsw, there is nothing exotic about these relays. You can buy a generic copy of this universally used Bosch type 5 relay almost everywhere now. Would not be surprised if Wal Mart has them. Or you can go to any auto parts store and get them for real cheap (under $10) and they will plug right in and work.
I suggest you put a new relay in the PTO clutch position and swap the other relay back to where you got it.

{{gwi:350142}}

Ok, I hope this is nothing. I got the relay 5 pin switch and plugged it in. If you remember I was out of gas so I also got gas when I got the relay. I poured the gas in and go to start the mower and the engine cranks but won't fire up. Because I tested the starter a few times during this entire process with no gas in the mower I figured it might take a bit more time to start. I tried it a few more times and no luck. The battery started to drag so I jumped the battery. Still no luck. The motor would turn but would not fire. Near the end the starter started to make a errrr noise so I stopped. I felt the starter and it was hot. I'm going to wait an hour or so and try it again. Hopefully the mower was just dry (no gas) and because of this I had battery/starter issues??? Please let that be it.

Did you return the "swapped" relay back to its original connector/holder?
If you still have the former PTO relay in one of the other connectors, that might be the problem.
Do not crank the starter for more than 10 to 15 seconds at a time with about 10 minutes cool down between tries.
You can place a fan to blow on the starter to hasten the cooling.
When you say it does not "fire", I presume you mean "It doesn't try to run".
So, unless you mean that you have checked for a spark at the plug vand found none, your next move is to determine if you have spark or not.

If you determine that you have spark but iut still does not try to start, dribble a spoon or so of gasoline into the carb throat, or give it a quick shot of spray carb cleaner.....DO NOT USE ETHER!!
If the engine tries to run on the "primer shots", your fuel system might simply not purged itself of air from the fuel out. Several attempts with the "primer shots" may help purge trapped air in the fuel hoses.
OK, I'm off the my Labor Day festivities, which means "I gotta go to work". Later

The funny and not so funny -
I sprayed quick start in the engine but that didn't help. It turns out the gears on top of the starter that engage with the engine were not making good contact. It appears over time that they have been ground down. I have noticed this before when the starter had gotten locked in the up position = in the engine gear. So I tried to adjust the starter to move it closer to the engine. Some of the plastic housing on the starter was cracked (heat)?. I put duct tape around it and tried to use duct tape and a popsicle stick to make one side of the starter higher so when I screwed it back on the mount it would be cocked/tilted toward the engine. After playing around a bit that worked. The starter now engages the engine and can still lower. Luck would have it that when I finally got it started and let it run for 10 minutes (with the engine cover off) that I forgot to put the engine oil dipstick/cover back on. So oil was spaying everywhere.

It looks like I may need a new starter down the road b/c I'm not sure how long my temporary fix will hold. I am bad about turning the starter when the engine is still turning trying to get it started. This is probably why by starter gear is so damaged.

Thanks Mownie and Bill for your help. Mownie, email me at nycjsw at yahoo (dot)com.

You have got to stop watching reruns of "the Red Green Show"

I just read this, and it made my day Mowie you must be a saint ? The guy with the relay prob, just hire someone to mow your lawn before you kill yourself :)

Just read the information regarding a PTO bypass switch. I did this on my John Deere LX188 and it works perfect.
The relay switches on my JD 188 are part of the circuit board for the ignition switch and are not removable. Put a new PTO on the machine as the other PTO was ruined by a water leak from the Kawasaki 2 cylinder water cooled engine.
Probably a safety issue but resolved the problem with the pto failing to engage.

Forgot to mention that I wired a 15 amp fuse in the circuit when I byplassed the pto switrch

Change that and your golden

I have the same problem