No problem, but I had to go to the store - so a lot of info was left unsaid.
1. If the system has been allowed to drop to atmospheric pressure, it will be contaminated by moisture and non-condensable gasses (i.e. air). It will be necessary to evacuate the system before even attempting to recharge.
2. More importantly, you still have the original R-12 service fittings. So it would probably be safe to assume that the refrigerant has never been converted to 134a (which I am assuming you intend to use).
Below is how I convert to 134a, ignore it if you are staying with R-12 - or if the conversion has already been done:
It is a good idea to remove the
hoses and tubing that connects the 3 main components (
compressor, condenser & evaporator) - then blow the hoses/tubing and components. The
oil will be far more effectively removed.
You can't blow through the compressor - unbolt it, and tip it over to drain the oil (rotate the internals if possible). This will get the bulk of the R-12 oil out.
Here is a
134-A conversion procedure written by someone with too much time on his hands:
No component changes are required to
switch over from R12 to 134a. All the currently installed
parts can remain and will work just fine with a 134a charge. While the system is open you will want to replace the filter drier and the expansion tube.
Couple of notes:
You will have to dump the remaining R12 before anything else is done.
You can legally release it to atmosphere, but certified shops cannot.
They have special re-re (refrigerant recovery) equipment that captures the R12. When they have a
full bottle it gets sold to a facility that purifies and repackages it for re-sale. The production of new R-12 was banned worldwide years ago, so the only source is what can be reclaimed.
Anyway, if a shop does this conversion, that recovery process will trigger an extra charge. If you do it yourself it is free.
Whatever way you do it, after the
system gets dumped, it will need to be flushed, evacuated and recharged with 134a.
Flushing is required because the oil used with R-12 is non-compatible with the
oil used with 134a. There is a specific, involved, expensive way to do this - or there is the easy way. Provided your system is not being changed over due to a "black death" casualty you can do it with all the components in place and using just compressed air.
Black death is simply a term used to describe a refrigeration system that has been disabled due to a catastrophic failure of the
compressor. All the components and connecting tubing/hoses are contaminated with burnt (caked on)
oil and all the metal particles that resulted from the compressor failure.
Release all the tubing fittings that connect the 3 main components (compressor, condenser & evaporator). Remove the suction/discharge hose manifold from the back of the condenser. Pull the existing expansion tube from the tubing that leads into the evap. Remove the filter drier.
Using 100 psi compressed air at a good volume:
Blow the residual
oil from the condenser and evaporator
coils. Do this in in both directions. Repeat until you feel that the bulk of the old oil is removed.
Blow out the liquid line that connects the condenser to the evaporator.
Blow out both compressor hoses.
Understand that the old
R-12 oil is not like "poison" to the newly added 134a - its just that it does not behave in exactly the same manner. So if there is a bit that remains in the system it will not be an issue.
That's it for flushing.
Using new o-rings at the fittings, replace your
filter drier and expansion tubing.
Add
PAG 100 oil in quantities as below and close the system up.
•Compressor- (1 ounce)
•Evaporator - (3 ounces)
•Condenser - (1 ounce)
•Accumulator (2 ounces)
Evacuate, leak check (
system should hold 28" Hg for a few hours) and charge with about 50 ounces (4 cans) of 134a. You will have to jump your low pressure cut-out switch to get the first 2 cans in. After that the
system will have enough pressure to allow the low pressure switch to operate normally and keep the compressor running.
You will need to buy a set of adapters for the
service ports so you can charge and attach your gauges - if you have them. The adapters just screw on to the existing service ports.
