shaking split ac unit

[hayhay]

today I came across a split ac unit & everytime it's turned on it begins to violently shake for a second or two and then shutoff. I have to get it up and running for a trade school project and I have no clue were to start! before this I've mostly only worked on small units, so it's a little new to me. I've never seen anything like this. please help me? thank you

[Redwood650]

Well, which part of the split is shaking? The condenser or the furnace? If it is the furnace, check the blower wheel and make sure the bearings/wheel is ok.

[Gross]

sounds like a fan problem either way....or one hell of a compressor issue.

[SwampTromper]

Sounds like compressor issue and its shutting off on thermal overload and/or pressure safetys. Was it rigged for a problem or a normal unit that just started doing this? I don't see any fan or blower issues to cause such rapid shutdown on residential unit. Can't be much help without more info.

[mgenius33]

Single or three phase?
If it's single check the cap wiring and size, and then the refer pressure.
If it's three reverse any two lead and then check the refer pressure.