Well, in a nutshell, when you run a system with a partial loss of charge you decrease the systems ability to use the suction gas to cool the motor in the compressor. The motor starts to overheat. As the motor overheats the insulation on the windings begins to break down and disintegrate to the point where the windings short out. ZAP, you now have a fried compressor and maybe a burn with acid, (from the broken down insulation) now in the system. Your method will work for a little while, but nowhere near as long as you figure. Pay now or pay later. The older the system gets the less economical it is to sink dollars into that old system.

Sorry, a bit more clarification. My AC guy told me he found a leak in teh evap coils of the air and that he will need to replace the entire unit with new govt regulations. The compressor is only 5 years old and the air handler is 13 years old.

But, now I'm reading a post below, and he seems to be full of doo-doo. Can I just replace the coil? Thanks

Ah, so I knew there was a reason to consider a change :-(. So, can I have someone simply replace the coils for less than 3000 dollars?

Find a different service guy. All you need to do is repair the coil. Many times a coil is replaced rather than a repair. If the leak is in an accessable place it can be repaired easier than replaced. The problem is warrantee of a repair. A typical customer will complain when the coil leaks again. Many coils are replaced with this logic.

First of all if you have an air handler thats 13 years old you may want to consider a replacement. Just not with that guy, thats all. A leak repair in a coil in an air handler can be a royal pain in the butt. The actual repair of the hole or crack can take less then 5 minutes but you can easily spend half a day taking the thing apart to the point where you can access where the leak is. So now you get a bill for all this labor etc. which will probably give you "poopy pants" and somewhere in the not to distant future another problem arises. Maybe the blower motor quits, or the drain pan has rusted out and water is leaking all over, if its an air handler in the attic you probably made a hell of a mess to your sheetrock ceiling and if its over a furnace who knows what damage it can do in there to cost you more bucks. And heres another scenario. That old unit was rusting out and the blower bracket lets go. You hear one hell of a racket coming out of your duct work, (oops, more poopy pants) and you find out the whole blower assembly has to be replaced. But the unit is so old getting the right parts are almost impossible. So its 95 degrees out and no relief in sight for days. The service tech appears to be sympathetic to your dilemma but inside he's saying "serves you right you cheap SOB, I wanted to replace that POS when you first started having problems" So you try to make a deal, you ask him if he would be interested in a can of freon as part of the deal for a new unit. You say you paid over 300 dollars for it and only used a few pounds. The guy says sure, I'll know off 50 bucks to take it off your hands and I'm doing you a favor, you're not supposed to have the stuff anyway! One of the interesting side bars of the heating and air conditioning trade is that you collect sooooo much money from some people whose original intention was to save themself a few bucks by doing it half as---!