I have a MTD yard machines lawn mower. I have put a new engine on it and the charging system is putting out ac volts instead of dc. Every time I try to hook up the charging wire, the dc volts on the battery drop and the mower shuts off. I don't know if there is a converter I'm suppose to hook up or something. Other than this the mower runs good. I just jump it off and mow my grass, but that's getting old fast.

Hi,
It may be that your replacement engine requires a rectifier that did not come with it; it would depend on the version of engine and which stator it came with. Briggs uses shapes and colors on its stator connectors to distinguish them.
You could provide engine numbers and a description of the stator connector there at the starter and dipstick area.
Peace,
Clarke