I have a 200 silhouete, v-6 3.4 it blows cold air thru the front vents but hot air thru the rear vents, i have messed around with both front and rear controls and still no cold air on the rear vents

Not likely, but Is Hot water flowing to heater coil in back? How hot is "very hot" Is it a refrigerant line? If a refrigirant line, Very Hot means it is hot gas from the compressor that "should be going to the condenser coil usually in front of the radiator. It's almost impossible for that Hot refrigerant gas to go to the cooling coil in the back unless you had some repairs done and they weren't certified. My guess is the radiator hot water is not being controlled properly, due to bad valve or control system components.

could be blend doors in heating duct work.

Usually a sign of a faulty blend door under the dash.
The blend doors direct air thru the ac and heater core along with the upper and lower vents.

Could be a blockage in the lines to the rear unit.
Might be low on freon too. Or a blend door problem.
Can you check under the floor and see if one of the lines is cold ?

you have a vacuum leak in the selector switch for front heat explorers had similar problems

is it just the hot air that wont blow, or is it both hot and cold?

Hard to read your question, do you mean it blows cold air out of the front vents and hot air out of the rear passenger vents?

If the air coming out of the front is just cool and not cold, and the rear vents are warm, you have low freon and need to have it serviced.

Hello according the the manual, the back vent are to blew cold air only..the fronts vents are suppose to the entire car...

check you antifreeze level and make sure its full