A/C Flushing

fastsc92

Registered User
How should I flush my A/C system? Right now I have R-12, but I want to flush the system and change over to R-134a. Can I flush it myself, to get the old oil out? If so...how can i do it? Air Compressor? Do I need to bring it somewhere? How much am I looking at if I just bring it somewhere and have them flush it, and not charge it? Any help on this would be great. Thanks
 
Take it to a shop and have them evacuate the A/C system. I have done this a few times and the shop I take it to charges around $20. It usually takes an hour or so and they can tell you if it holds a vacuum. If it drops off as soon as they turn the machine off thats bad, and it means there is a leak somewhere.
 
You can flush it yourself if you want. As long as your compressor is in good condition. What you have to do is disconnect the hoses at the condenser, evaporator, accumulator and back manifold of the compressor. There is a special tool to loosen the spring lock fittings to unhook the hoses. They sell them for around $10 at auto parts stores.

If you're going to do this on the car, you'll need either a compressed air, or a special pump to blow out the parts. If you remove the parts from the car, you can get by with lung power and some hose, or an air pump (like for air matresses, etc.)

Starting with the condenser (cooler in front of the radiator), fil it with some flushing solution and push it in with air.. let sit for a few minutes and push it a little bit more. Repeat until it starts draining. Catch the outflow in a suitable container. Then blow it out, and repeat until the flushing fluid comes out clean. Then blow it out good and let dry for a few hours.

For the hoses, fill them mostly with flusing solution (brake parts cleaner works good), let sit, blow out. If you catch and filter the outflow, you can probably reuse the fluid a couple of times. The suction hose (the hose which goes from the accumulator to the compressor) should be filled from the compressor manifold and pushed out the accumulator end. The high pressure hose likewise should be filled from the manifold and blown out the condenser end.
Note: The liquid line should be filled from the evaporator end and blown out through the condenser end. This is because you have a fixed orifice tube filter on the condenser side.. you want to push the contaminants back out.. not forwards.
Be sure to let the lines dry for a while to remove all the flushing solution.

On the evaporator (the part inside the car with the 2 tubes sticking out the firewall), push the solution into the top fitting (the inlet) and push out the lower tube (the outlet) which hooks into the accumulator (black steel canister with a wiring connector). You will need to remove the accumulator to get the fitting opened. Its a bit of a pain, but doable.

Now, as for the accumulator, I'd advise you replace it (around $60), but if you decide not to, then cap it immediately to keep it dry as possible, turn it upside down and let it sit for a while, then drain the oil out from the front facing tube. Don't flush it! The solvent could cause the dessicant bag inside to break and that'll ruin your system. Measure how much oil you recover.

As for the compressor, don't flush it either.. turn it by hand for a while until no more oil comes out. Likewise measure how much oil you recover.

Refill the accumulator and compressor with the same amount of PAG/POE as came out of them. Then add enough PAG/POE to bring the whole amount to 10oz. Including what you put in the compressor+accumulator. Spread it out between the condenser, evaporator, accumulator and compressor (1,2,3,2 if you needed 8) and install NEW Orings and lubricate with nylog (what the pros use) or mineral oil (yes even for 134a) on the tubes.

Now, snap it all back together, and bolt the manifold back on the compressor and intall the required r134a fittings.
Promptly take it to have it vaccuumed out and charged with refrigerant.

Also, check out this web site: www.ackits.com/mastercool/flush.htm
lot of good info there, and they sell just about every thing, including a flushing kit.

Now, if all this sounds like too much, call around and get a explanation of the work and prices from a few shops, ask a few questions about the procedure they will perform, and take it in. They have equipment to do the job a lot faster than us.

Hope this helps.:)
 
yes..thanks man....that helps a lot. I think what i'm going to do is have a shop flush it out and get it ready to be filled, and i'll just get one of those a/c retrofit kits and fill it myself. If the system is flushed right, then it should be fine if I fill it with that kit. At least i hope so.
 
You might save $50 or so doing the charging yourself, but if the shop can vaccuum it down and it holds the vaccum, you should charge into the vaccuum. Think of it sort of this way; with a vaccum, the refrigerant will be sucked in.. not mearly pushed in by the pressure in the can. Also, with a vaccuum, you will have almost no air in the system to start with. Air=bad.

Be sure to bleed the air from the hookup tube before you hook it up. The instructions should tell you how. Then charge into the BLUE fitting. Once the system has sucked in all the 134a that it can, start the car and engage the compressor to suck in the other can(s).. You want about 32oz, 34oz tops, of r134a.. Don't overcharge it. Don't turn the can upside down either as that sends liquid refriegerant into the compressor; warm it if necessary with a bowl of water at around 120 degrees.

I believe they state that you run the A/C on norm/high with the windows down at 1500 RPM to get the final proper amount in.
So, its 3 stages: off, idle, fast idle


And if the compressor won't engage on its own, unhook the pressure switch and jumper it with a paper clip. Thats the connector on top of the accumulator.

Needless to say, you're better off with a set of guages, not just the 1 they put in the kits. Being unable to see the compressor outlet pressure is sort of a shot in the dark; but at least we can tell you the amounts, so it should be a well aimed shot.

If you do all this, you should have good results.. the industry standard (albiet a sucky one) is 30 degrees below ambient which means basically, if its 100 outside the you should get at least 70 from the vents on NORM with the windows open at idle. Norm means its taking in the outside air and cooling it, max means its recirculating the inside air and cooling colder and colder air. You will get much better results when the car is moving obviously. You should see vent temps in the 40s. :)
 
Back
Top