Is there a way to build/connect the following items to an AC system
and have it evacuate all of the refrigerant.
1. Manifold gauge set
2. 2cfm 2-stage vacuum pump 110v
3. emty propane tank.
My understangin is that the commercial units costing $4,000
essentially are built fromthe same components.
I have no plans to reuse the old 134a. All I want to do is
depressurize the system so that I can replace a bad compressor.
I have the manifold gauge. I bought it on Ebay for $25
I'll cost $30 to rent the pump for the weekend.
The propane tank was free.
2 cans of R-134a is about $12
I can purchase a brand new GM HT6 compressor for $220
I've called some ac shops and dealers and they want between $600 -
$1100 to do the job
If you have any refrigerant left, you can pump it out of the system into
an approved tank (but I am not sure the propane tank would fit that
requirement). You can even chill the tank with something like dry ice
to make the job easier. What do you intend to do with it then??
GM compressors often fail at the front seal and the refrigerant is mostly
lost anyway. Do you know if yours has a significant charge?
The sealed system may have a lot of contamination in it. Do you intend
to flush it and replace the expansion device (orifice tube or expansion
I have to do this job soon on my van to replace the evaporator core.
I might have a little refrigerant pressure left, but have no intention
to try to recoup the couple of grams of refrigerant. It will be just
It does take some expertize to do the job right/safely. Not knowing
what the gauges are 'telling' you can lead to a dangerous situation and
damage the ac system. None of it is rocket-surgery though and is easy
enough to learn.
As to evacuating the system: I'd suspect that was done already by the
compressor when it gave up. The gauges will tell you that. A vacuum
pump might be a good investment in the 'long run'
Those evacuating systems not only capture the refrigerant but also
clean/recycle it for reuse.
On Thu, 17 May 2007 08:26:53 -0500, email@example.com wrote:
I have the factory service manual for the truck that explains in
detail how to diagnose and repair the ac system. As long as I keep an
eye on the gauges and I don't open the high side while recharging,
it's pretty safe and starightforward procedure.
The manifold is in the process of being shipped so I don't know what
the pressures are. Assuming both high/low sides read zero, what is the
possibility of liquid refrigerant still remaining? If there is a leak,
will all of the liquid refrigerant boil off in a matter of a few
seconds once the atmosphere enters the system?
The whole system must be flushed. This procedure can not be
side-stepped. De-natured alcohol pushed through the lines under
pressure will do the job. Compressors are not a piece you want to
replace often. The orifice tube must be replaced and the accumulator
should also be replaced. Follow the procedures for adding oil into the
system. Check every connection for signs of leaking. While the system
is 'down', I'd replace the O-rings at all connections. Doing the job
right will be rewarded with a trouble-free AC system for years to come.
That is because compressor failure usually means you have a LOT more to
do than just replace the compressor.
To start with you need to evacuate the system.
Then pull the compressor and the lines to the condenser to see how much
crud from the failed compressor made it into the condenser.
Then you need to flush the condenser (IF it can be flushed,some cannot)
Then you replace the accumulator/drier because of the crud from the
compressor and the orifice tube is probably plugged as well. That gets
you back around to the evaporator which will need to be flushed at
least. Now that the system has been flushed and the plugged parts are
replaced you can reassemble the system (add the proper amount of oil to
the compressor & add an inline filter just in case you missed some crud)
and vacuum it down and see if it holds. Then recharge the system.
THAT is what the AC shops will do. If you JUST replace the compressor on
a failed system you may as well take the money your spending on the
parts and tool rental and burn it. Why? Very simply the new compressor
WILL suck in debris from the failed unit which will destroy it in short
As I suggested in my previous post, and in total agreement with Steve W.,
you may well need to flush the system even if you have not had a major
I just did my Reatta and upgraded it to R134a. It did not have a major
failure, just an R12 leak at the front seal. It was not even a big leak.
We did the job correctly. We replaced the compressor AFTER removing
the expansion device and filter/drier and flushing. It was full of black
There is a right way and a wrong way. You may get away with doing a
halfway job....for a while.
Even doing it the right way should not cost $1100.
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