I think most folks use a solvent based solution to cleanse their AC systems.  I don't think it's a good idea to introduce H2O to the system, and it won't lift much of the accumulated grime in there anyway.

I'm certainly no AC expert, but I've often heard that the expansion valves are frequently the choke points for system blockages.

Sent from my iPhone

On Sep 4, 2011, at 8:46 AM, Karl Wolz <wolzphoto@Q.COM> wrote:

> '85 Westy with 2.1L, using R-12
> 
> Only blowing around 80 degrees (better than 112, but not by much), mechanic
> says 300lbs high side pressure and only about 10 lbs low side.  Says he
> suspects a blockage "somewhere".  He drained the R12 and blew through the
> condenser - says that's clear.
> 
> Due to my ingnorance of things AC, the hoses were initially hooked up
> backwards at the compressor.  Mech says running the system in reverse may
> have damaged the receiver/dryer, causing these symptoms.  Last night I
> pulled out the expansion valve and am able to blow through it.  AC parts guy
> says that means little, as it could be locked open or closed (this means
> little or nothing to me [I feel like Rocket with this series of questions]).
> 
> I bought brass fittings last night with which to hook up a garden hose to
> the system (sans compressor & receiver/dryer) to hopefully flow out any crud
> hiding in the system, with the logic that any water inside will be boiled
> off when a vacuum is pulled prior to recharging.  Anyone care to comment on
> the wisdom of this procedure?
> 
> Hoping for cooler air,
> 
> Karl Wolz