I need to replace the a/c compressor. Purchased the unit and it look easy enough to replace, but the guy at the parts store said DO NOT drive the truck until I have recharged the unit. Didn't really seem right, and he really couldn't explain why, just said don't. Is there any truth to what he said? Or can I replace the unit then drive to the shop that will vacuum and recharge the system? He also said that I needed to add oil to the compressor before it was driven as well. Obviously I'm not a master mechanic, and any advice would be appreciated. Thanks in advance for all of your help!

 

If the guy knew how to do AC system service, he wouldn't be working in a parts store for $9/hour.

If the system is not charged, it simply will not operate, the pulley will just free-wheel. The system has to have it's oil installed before the system is operated. Some compressors come with it already installed, some do not. Read your instructions that come with YOUR replacement unit.

 

I know most recommend to change out the drier unit when ever opening the charged system.
Hopefully taking it to an a/c mechanic will get it right before activating.

 

I don't know of (any) Replacement A/C Compressor that will be Warrantied if you don't replace the Receiver Dryer and at least the Orifice Tube. You didn't say how or why the original A/C Compressor failed. If it Seized there will be substantial contamination throughout the A/C system. All of which will need to be replaced before your A/C will work again. In addition to the Compressor and Receiver Dryer, I've seen Condenser, Expansion Valves, Liquid Lines even Evaporators become contaminated after a Compressor failure. All of which require replacement before the A/C will work again.