Automotive Air Conditioning Information Forum

tbirdtbird wrote: ↑Mon Jun 07, 2021 12:01 pm Just noticed this,

" Since I completely charged the system with refrigerant before start up"

Details on that if remembered. How deep a vacuum, type of pump, etc, the questions go on. Use of refrigerant scale, vacuum gauge, etc etc.

I only bring this up because you are essentially starting over....

Pretty much "shade tree" answers to those questions. Harbor Freight pump. Vacuum to -29 (edit: for probably an hour), which I think is normal at 1,000 ft elevation. Small cans R134a, no sealers, PAG 150 preblended with dye, no micron gauge.

(Pre)charging consist of a process that does not require the compressor to run. I do it by pressure difference... heat the can, fan on the condenser. The original vacuum gets you better than half the first can for free. I usually figure 11oz per can, because I purge the yellow line on each can before turning the low side valve on the manifold back on.

If anyone ever wanted exactly so many ounces and a half outta me... I'm afraid I'm not that precise. I kinda thought these old cars were a little forgiving when it comes down to fractions of ounces, compared to the newer cars.

"(Pre)charging consist of a process that does not require the compressor to run. I do it by pressure difference... heat the can, fan on the condenser. The original vacuum gets you better than half the first can for free. I usually figure 11oz per can, because I purge the yellow line on each can before turning the low side valve on the manifold back on."

Would love input from other members on this method.

Harbor freight has several types of compressors, including the venturi type which is essentially junk.
I personally think if you are gonna flush that you should run the pump for 1.5 hrs anyway, and I would triple evac
The retard scale on the low side gauge is anything but accurate.

You'll never get all 12 oz out of the little cans anyway

ERROR
Harbor freight has several types of compressors, should be several types of vacuum pumps, sry

"Harbor freight has several types of compressors..."

The Harbor Freight item was the vacuum pump. I'd post a link to one that I think is it, but not sure if that would violate forum rules. Suffice it to say, it was around $100 a couple of years ago. Pretty sure it's the one they have for 89.99 these days.

As far as the air source for the actual flushing, I have a 60 gallon upright with a 12 foot tall dewpoint dryer mounted on my shop wall, with a filter/regulator at the output side. I haven't sandblasted with this dryer yet. But I did test it's drying ability by doing a 45 minute continuous open flow through a blow gun. Aiming at a piece of cardboard revealed not a single drop of moisture made it through (for that test). The humidity was fairly high during this test as well.

The velocity, volume, dryness, and cleanliness of the air are things working in my favor. Also, I have the ability to supply "purge air" indefinitely, without having to hold onto anything. Lack of agitation is my only concern. But the TFC is not on the vehicle. So I could always "shake it around" to create agitation. The evap is mounted however.

tbirdtbird wrote: ↑Mon Jun 07, 2021 12:43 pm "(Pre)charging consist of a process that does not require the compressor to run. I do it by pressure difference... heat the can, fan on the condenser. The original vacuum gets you better than half the first can for free. I usually figure 11oz per can, because I purge the yellow line on each can before turning the low side valve on the manifold back on."

Would love input from other members on this method.

To me, this method (I presume charging liquid refrigerant) seems like more trouble than it's worth. Why go through all of that when in just a few minutes, you can charge refrigerant gas safely and precisely through the low side into a well-held vacuum using a professional-grade refrigerant scale, a quality manifold gauge set, and a 30-pound cylinder (or small 12-ounce cans, if you choose to ramp-up the difficulty somewhat)? Or, if you have one, using an RRR machine?

any engineers in your family...