Cub Cadet,model 2135. Is there a relay betwee switch and electric pto?

May be electrical connection/wiring, safety switches issue. Do you have power to PTO.
https://www.youtube.com/watch?v=fIeTNfn4fGc
https://www.tractorbynet.com/forums/cub-cadet-l-g/340940-pto-will-not-engage.html
https://www.tractorbynet.com/forums/parts-repairs/290384-cub-cadet-lt1050-pto-problem.html
https://www.youtube.com/watch?v=UsntNTb3y1Y
https://www.youtube.com/watch?v=pUNDzfDQk0c
https://images.homedepot-static.com/catalog/pdfimages/ec/ec85ed98-2dbc-4952-9d13-88053dca9e6c.pdf

Winding in electric clutch grounded, hopefully just wire going to clutch as these get torn by sticks etc. and ground against frame. Also could be bearing gone out in clutch causing bad clutch coil windings to go bad.

There are several things that can cause the fuse to blow. PTO stands for Power Take Off and most likely this will not be the problem unless it blows the fuse when it is turned on. What you are saying is the fuse is blowing by just turning on the switch will be a short which can be anything from a pinched wire, shorted diode, short in the stator. bad voltage regulator.etc

IF connecting that one hot wire to the pto made it engage then you either have a broken/cut/bad connection/wire to the pto or the switch is bad.
What you did by using the hotwire to the pto is bypass all the wiring and the switch for the pto.
You can determine if it's the switch real quick if it only has two connections/wires to the switch. Pull the switch, remove the wires and touch them together, after you have the mower in the condition under which the pto would engage. If the pto engages it's the switch for sure.
Take all the proper safety precautions. Don't let the wires touch anything else.

on my cub the blades keep shutting down when im mowing . I replace the pto switch and it doesnt help .. got a recommendation

Sounds more like a PTO clutch failure, rather than the switch. The clutch is mounted on the engine shaft, between the hydrostatic drive pulley (nearest the chassis) and the mower deck belt pulley (farther from the chassis).
Since it's an expensive part, make sure the problem isn't in the switch or wiring first. You could do that by probing the wires to the PTO clutch with an automotive test light - they are inexpensive and handy. Clip the ground wire of the test light to the chassis, and probe the hot wire to the clutch (it's the one that doesn't connect to ground) when the engine is running and the PTO switch is engaged. Obviously a helper has to be in the seat, and you should be careful doing this. If the light glows brightly, and the clutch doesn't engage, you definitely have a bad clutch. Good luck! Please rate my answer if helpful, thanks.

check wiring and fuse maybe switch

if this an older machine i would unpug your ign switch,and your pto switch and your relay and check to see if you have a faulty connection or rusty terminals either on the switch male spades or the female plug.clean or scrape with emery cloth,sandpaper or a pocket knife.spray with electrical contact cleaner.using a twelve volt test light check for voltage going from ign switch to your pto switch--- yes---,then test for voltage to your relay. if ther is it should then go from your relay diectly to your clutch and you should hear a click or your cltch will engage. if not check plug in on your harness to clutch harness.clean terminals.test clutch by using a test lead from positive to one of your cltch wires and anothe from the other wire to ground ,if good it will click.good luck

you have a wire that is shorting out somewhere, i would trace the wires from the clutch all the way back to the fuse including the relay and pto switch. You will more than likely find your problem in the control circuit between the fuse, pto switch and relay since this is what is fuse protected.

I had the exact same issue early this mowing season on a LT1045 with 184 hours on it. On a wild hunch I lifted the seat and simply sprayed the PTO shut-off safety switch with electronic contact cleaner/enhancer and have had to problems since.