Z425 JD zero turn

Bought new in 2011. Kept all maintenance up. Recently while mowing it died. Started it again and when engaging mower blades it dies. Not a safety switch problem. After a day of not finding the problem I locked out all the safety wires and it still dies when blades are engaged, other than that it runs perfect. Anyone have any ideas??
Thank you.

Remove the deck drive belt from the pto clutch pulley and then try to engage the deck. If it keeps running then the problem is in the deck. If it still dies then need to start looking closer for electrical issues.

I found the problem. Seems there are 2 ground cables, One from the battery to the motor and one from the deck pto clutch. The nut on the pto clutch ground cable loosened and came off, I put a new nut on and it fixed the problem.