I have a 2008 Scag 36" walk behind (belt driven) with probably 50 hours on it. I've had a few problems in the past with the engine dying when I place the transmission into gear. Some fiddling with the Operator Presence Switch and it seemed to be OK. The other day I just started mowing and after 30' or so it dies. This has never happened before. I was able to get it started but now if I engage tranny or blades it dies. If I remove the tranny switch then engaging tranny is fine. I tried jumping the Operator Presence Switch and it still dies engaging either. The blades or blade drive mechanism is not jammed as they turn easily. It definitely seems like an electrical kill and not a mechanical kill. It's possible the tranny engage and blade engage are entirely separate issues and both have become issues at the same time. I did some voltage checking at one point and was surprised to find a varying voltage between 20 and 28 volts on one of the wires on the blade engage harness. Guidance?