Mower deck Cub Cadet 1515 PTO issues

Hello all, just got a used cub cadet from my brother-in-law. I am having issues with the PTO, when I first got it the PTO used to disengage by itself and reading some of the posts it may have something to do with the seat safety switch, some say that the safety switch under the seat is used to disengage the blades, mine kills the engine. Any way now the PTO disengages by itself even when the lawn mower is not moving (the engine is running). I just ordered a new PTO switch, will be double checking the safety switch under my seat. It痴 my first lawn mower and I believe I am the 3rd or 4th owner. Any suggestion on what the problem may be??

Thanks,

http://cubcadet.custhelp.com/app/answers/detail/a_id/1722/~/cub-cadet-professional-shop-manuals

http://service.mtdproducts.com/Training_Education/769-02100/1000_1500_series_shop_manual.htm try adjusting air gap at PTO clutch

http://www.messicks.com/Articles/FixingElectricClutch.aspx

https://www.google.com/webhp?source...v=2&ie=UTF-8#q=how to troubleshoot pto clutch

The electric PTO will disengage all by itself any time it gets too hot or when the voltage drops.
This is done to protect the PTO.

I'm checking on this for a friend of mine with a Cub Cadet. He says he can engage the PTO and it will stay engaged when the mower is at a crawl but if he increases the speed at all the PTO will disengage. He has to re-engage the PTO at idle.

I suspect he may have replaced the battery with one not rated for his engine. I haven't looked for myself yet. He says it's a new battery and will struggle to start sometimes. If I am correct and the battery is under rated, would this cause a drop in voltage if he increases the mower speed and result in a safety PTO shut off? I would have thought an increase in RPM's would result in an increase in voltage, but I know next to nothing about electrical systems! Could the problem be related or does this sound like something else altogether?

Thanks folks!

An update... I replaced the PTO switch and it works better, if I go over a bump it will disengage the PTO. But it is better than before.