Never "flush" an A/C system with anything!!!

The following are "standard" procedures.

First you should remove the compressor oil and replace it with new. Consult the dealer for the type and quantity. (note refrigeration oil has to be wax-free oil unlike standard oils) Whatever the recommended quantity, you only want to add 95% of that figure. (about 5% always remains inside the compressor). Do not overfill the oil level.

Next assemble the system using all new gaskets and hoses. Nothing like putting the entire system together to find that you have a leak in some awful spot to reach and it is due to a reused gasket or o-ring.

Now leak check. Simple method. Using a nitrogen bottle and a regulator, pressurize the system to 120#. Disconnect your guages from the system, install new caps on the access ports and let sit overnight. If pressure is 120# in morning move on to evacuation below.

Finding a leak...well here is a simple method... Pressurize the system back up to 120#. Using a mixture of 15% liquid joy dish soap, 10% glyceron (from local drug store) and 75% water in a spray bottle, spray all the joints and connections. Leaks will show up as bubbles that grow. If this doesn't work, more extensive equipment will be required.

Evacuation - using a vacuum pump, pull a vacuum to below 29" on your guage. Once there, leave it go for another hour. Care must be taken to close all the valves before turning off the pump or air will suck back in.

Charging should only be done under the direction of a trained professional. Using proper proceedures, purge the center hose and weigh in your charge.

Now with favorite beverage in hand, climb into your vehicle and enjoy the a/c.

Good Luck!

 

Compressor oil (which moves thru the whole system) is removed with a special flush that costs ~$16 / pint. The flush won't affect the new oil or refrigerant, so it's not necessary to remove the residual flush other than blowing it out with compressed air. R-134a causes mineral oil (the type used with R-12) to gel, so R-12 systems MUST be flushed before converting to R-134a. The oil used with R-134a is PolyAlkaline Glycol (PAG), and although Ester oil is marketed for it, it's not recommended by vehicle manufacturers.

Most new Ford compressors require unusual low-viscosity PAG oil (PAG 46), so don't use standard PAG oil in R-134a systems. Most retrofit kits include PAG 100 which will damage Ford compressors.

New O-rings & dessicant (inside the accumulator/drier) are compatible with R-134a & PAG oil, but old ones aren't, so they should all be replaced on any vehicle made before ~'92. Prelubrication of external O-rings should always be done with mineral oil because PAG will cause rust.

When coverting an R-12 system to R-134a, be sure to use the R-134a orifice tube (usually red compared to the blue R-12 tube) for proper performance.

 

Most of the flushes I had found left some sort of residuals in the system. Thanks for the tip on "Clear All". I will look into it.

Second note: my first post is strictly for servicing a system that has been open to atmosphere, not for a refrigerant conversion. Obviously, a conversion requires additional steps.