lawn tractor not charging

I don't want to hijack RRR's mower thread so I will ask this here! Since it is so hard to get up and down, and I have no love for small engine stuff, I take my mowers to a small engine shop, and so far I have not found one worth *** and save myself when I have to work on my old cars. Latest issue is the 7 year old Cub Cadet and charging. The last "mechanic" replaced the "what you all it" that charges the system, but it ain't working. I called CC tech twice, they sent me a electrical diagram that I can not read and the "tech" knows where to put in the gas and thats it.

Whats up? Bad ground? New part bad? Should not the charging system be really simple?????