Excellent point. I mean, why not? I figured it would be too difficult to flush the entire system; however, now that I look at it, I see that it's doable. Thanks for the encouragement.The only things I would point out are that the receiver/dryer absorbs moisture so you don't want to leave the system open with the new dryer installed.
If you already have everything removed from the vehicle and are replacing the condenser,dryer, and the compressor, and then flushing the hoses, that only leaves the evaporator and expansion valve to be flushed and cleaned. Would it not be easier to flush and clean that before putting it back together? Then once the evaporator is clean, put it all back together, vacuum it down and then add a fresh charge. Make sure you properly charge the system with oil. You basically have a dry system with exception of whatever comes in the compressor.
As you can tell, I obviously don't hold a grudge and my memory is good but short. Apparently the same can't be said for you. Thanks for calling me out...it's always appreciated. /Sarcasm.Ah, Mr. Clark. We meet again. I'm still waiting for my "must replace" bolts in my timing belt job to bust too since I scorned replacing them. I appreciate meticulous, but I maintain that some folks overdo it.
It's true that water doesn't boil at -25. But I didn't submerge the stupid truck for crying out loud. The system was exposed to atmosphere for all of 2 hours during the job (the failure didn't vent the system) - and that was in an electrically heated garage. I didn't NEED to make any liquid water boil. 24 hours at -25 is plenty to allow mere evaporation to work fine. Any minute liquid water that was in there at the beginning was vaporized after that amount of time and the final pump job I did before recharge would address 90% of that. The dessicant pack (system never before opened) is plenty for the couple milligrams of moisture possibly left in the system. Not worth jacking up the cost of the job by 15% to improve on minutely. I'll fess up if it goes bad, but I highly doubt it.
Potentially good tip about the free tools at Autozone though. I forgot about that. My past experience with them has been that 80% of those loaner tools are worn out, but YMMV.
John, come on now . . . open for 2 hours in a heated garage? Seriously, how much moisture is going to get in there? Now if the system had been left open for a year, with the vehicle sitting outside, then you have a valid point. I appreciate that you're trying to ensure people don't do something incorrectly, but I've been doing automotive A/C work myself since the early 1980s and what was described above was FAR from being a hack job.I just didn't want anyone to follow your lead. It's a hack fix on your AC system and while you may get away with it, at least for a while, it's a good way to ruin an AC system.
manualman,It's been a rather long time since high school physics and gas law, but here's my answer.
If there is NO liquid water in the system, then once you reach a certain measurement of vacuum and the running pump is just holding that level, then it is not actually evacuating any mass. If it's not evacuating mass, then it's not removing any remaining water vapor. Basic conservation of mass.
Holding vacuum in a closed system over time CAN turn liquid water into vapor. In my case, that would have manifested as a drop in pressure. In the case of a motor pump holding constant gage vacuum, that extra water mass would be evacuated. Since my vacuum reading didn't drop any in 20 hours, it's reasonable to conclude that there was no liquid water in the system at the time I applied vacuum. So the difference between my vacuum pressure and the 'proper' one is limited. If we knew the total volume of the system and the humidity of the air in starting conditions we could calculate the actual water mass difference between -25 and -30. But I didn't bother because the answer is clearly: negligible and well within the desiccant capacity.