Blower motor

You have problems with one or more vacuum lines.
The flow of air is controlled by opening or closing ducts with vacuum.
Check the vacuum reservoir under the hood (probably a round plastic canister with two hoses attached) to make sure one of the spigots is not broken off (yeah, it's plastic) and the hoses are intact.
One of the hoses leads to the intake manifold the other goes to the in-dash control unit.

If you see no problem there, you will have to pull the control assembly from the dash and check those hoses too.

I wuld highly recommend you spring for ~$20 US for a Haynes manual for your Jeep. About any parts store will have them.
It will help you now and maybe keep some schlock mechanic (I know, I'm not talking about you guys) from ripping you off.