Summer is upon us, and many of our cars are equipped with Air Conditioning systems that have long since lost their ability to cool.
This article will cover doing a retrofit to R-134a, and charging your system so you can stay cool this summer.
This article assumes that your system has either lost all of it's coolant due to an old leak, or has been professionally evacuated. This article will not cover the evacuation procedure. That should always be done by a professional.
Your system has probably been open for awhile, so you're going to need a new receiver/dryer which collects all of the system's moisture, and since it has been open to humidity for some time, should be replaced.
The Receiver/Dryer is Honda P/N 80351-SH3-A11
You will need 8oz can of Ester oil, preferably the screw-top style, this will allow you to pre-lubricate your O-rings. You can also use an Ester oil-charge can readily available from your Auto parts store, but this will make it difficult to lubricate your O-Rings. The article will cover the screw-top style can.
You will also need about 3 cans of R-134a, I like the UV stuff, so incase you have a leak, it's easily detectable with a black light. You should also pick up an O-ring assortment from your auto parts store, get the green colored ones, I think the 24-pack is under $3. I'd get 2 of them just to be sure to have enough of the correct ones.
You will need to get some retrofit fittings, Interdynamics makes my favorite set, they are metal and come in a universal pack. These are screw-over fittings that go over the Schrader valves on your R-12 fittings, with integrated Schraders and are of a quick-disconnect type, Similar to air fittings.
As for tools, I highly recommend a set of R-134 gauges and manifold. I got mine from Harbor Freight, item #92649 which cost me about $40. You could get a cheap charge hose, but that will not allow you to measure the coolant in your system once it's charged.
I also got an R-134a venturi type vacuum pump, also from Harbor Freight, item #92475 and cost about $10. You will also need a way to hook your can up to your manifold, there are a few ways to do this, I prefer the fitting that screws on top of the can and incorporates a valve for opening the can. There is also a type that screws into the manifold and then wraps around the can and has a needle to pierce the can and charge that way. Either will do, but I recommend the L-shaped valve type.
Getting to work, you need to take apart all of your A/C lines, and replace all of the O-Rings. Most of them are pretty easy to reach, and come apart with a 19mm box wrench, if I recall.
Remove the old O-Rings, and replace it with one of the same size from your universal kit, making sure to lube them up with ester oil before closing the fittings, a wet o-ring will seal better than a dry one.
There are 2 10mm bolts holding the receiver/dryer to the chassis of the car. Undo your 2 hoses, and these bolts, to pull the dryer out. It's in a bracket held together with a Philips head screw. When replacing, make sure to clock the dryer the right direction in that bracket so the bracket lines up with the bolt holes, and the dryer lines up with the hard a/c lines.
The rest of your fittings are located on the firewall at the evaporator, one is on the pressure switch, one on either side of the condenser, one where each of the metal lines mate with the rubber hoses, at both sides of the receiver/dryer and finally where they enter the compressor. While you are doing the o-rings on your compressor fittings, pour about 2oz. of Ester oil into the suction side of the compressor. (the hole closest to the pulley) this will guarantee your system is lubricated properly.
After you finish replacing your O-Rings and dryer, your system should be completely sealed, barring the fact that you don't have any leaks in your condenser, rubber hoses, evaporator, etc. Most a/c leaks are caused by the O-Rings wearing out over time.
At this point, screw on your Retrofit fittings, making sure not to cross-thread anything. Hook the blue hose and yellow hose up to your manifold, we can leave the high pressure side alone, we don't really need it to get the system charged. The Harbor freight kit features a valve on the quick disconnect side to lock it into place, you need to open this completely to get it to seat on your fitting, and then tighten it down to lock it into place and depress the Schrader.
Close all of your valves on your manifold and hook the yellow hose up to your vacuum pump. The venturi type pump uses air pressure to draw vacuum, so hook your compressor up to the other side of the vacuum pump.
Turn your compressor on and set it to about 85-90 PSI. This will start pulling vacuum. At this point open up the blue valve on your manifold to allow it to pull suction on your system. You will see the gauge slowly drop into vacuum, and at around 90psi of pressure you will see the vacuum slowly reach the max of about 27-28 in-Hg. Leave this on your system for a good 5-10 minutes to let it reach full vacuum and pull all of the moisture out of your system. You will see a puddle of water ac*****ulating near the air compressor side of the venturi pump. You do NOT want water in your system!!
At this point, you can close the blue valve and disconnect your vacuum pump. Watch the gauge closely, and make sure the vacuum holds. If it drops this indicates a leak and you will need to repair it before continuing. Hopefully it holds perfectly, and you can continue. I will assume it does.
At this point, you are ready to take a charge. You can hook your can up to the manifold using one of the 2 methods mentioned above, I will assume the L valve for instructions sake. Hook the L-Valve up to the can with the valve in the full open position. Hook the other end of the valve to the yellow hose on your manifold. Close the valve completely and then open it all the way.
Now open your blue valve slowly and the refrigerant should flow into the system, you can see your gauge move from Vacuum to Positive pressure. You can also see it moving across your sight glass. The whole can will not go into the system without the compressor running, this pre-charge will allow it to run.
At this point start your vehicle, set the temperature to cold, fan speed to 4, and A/C button on. You should hear the compressor Click when you press the A/C button, and you can watch the can charge the system. To ensure you can completely empties, I like to submerse the can in hot water, which will cause it to completely rush into your system. Once it is empty, Close your blue valve, and remove the can from the adapter valve. Add your 2nd can and close the adapter valve, and open it all the way, then open up your blue valve and repeat the same process. Do this until the pressure reaches the "full point" this can be determined using a chart, I used the one from the 95-97 Civic HELMS manual, which is a similar system that came stock with R-134a. For example, on an 80 degree (Fahrenheit) day, about 45-46 psi on the blue gauge @ 1500RPM.
At this point, your system should be fully charged an operational. If you have any Freon left over, DO NOT just vent it into the atmosphere, close the valve on the adapter fitting and save it incase you develop a leak in the future, or use it on a friends car or something.
These same tools and techniques can be used on other cars, and newer vehicles already equipped with R134a. If you wish to use an alternative refrigerant, such as DURACOOL or FREEZE-12, it is also very similar. The pressures will differ, but the technique is the same. DURACOOL uses a R134a can and fitting, I'm not sure about FREEZE-12. I believe both of these are propane based, and I have heard rumors that all future refrigerants will be propane or ammonia based.
If you have any comments/questions you can reach me @ henry_at_crxohio_dot_org.