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HOW TO: DIY Cold AC with R-134a on a 1988-1991 Civic/CRX

24788 Views 38 Replies 15 Participants Last post by  NovaVTEC
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.
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Nice write up, and well timed too!

I've used Duracool. It is a propane based refrigerant. It works very well. Unfortunately, my system has a leak in it somewhere, so I'm going to have to track that down first before I can recharge my A/C again. Luckily, I had a shop put a squirt of UV dye in my system after they pulled the vacuum on it. Hopefully I should be able to find the leak at night with a black light.
I've used that dye before with great success, I just used a blacklite bulb screwed into a trouble light and found my leak in minutes :)
I would really like to try duracool, but after doing a proper vacuum on my system this year, it cools the best it's ever had with 134a.
Does duracool use 134a fittings? do you know if it's compatible with Ester oil?

Duracool uses the same o-rings as R134a and uses the R134a fittings for charging purposes. I found the whole oil compatibility thing to be bit confusing, so I went with an inert and universal oil called ROCoil. It is compatible with Duracool, the o-rings, and any residue ester/PAG oils you have in the system from your previous charge.
How much were you charged for the vacuum?

Duracool is illegal in the states, btw. But I ordered anyway. R134A sucks and kills R12 compressors.
I bought the vacuum pump from harbor freight for about $10.

I have run R-134a for over 4 years, and the only problem I ever had was that my pressure switch stuck last year and the pressure got so high that it popped the safety plug on my dryer. As long as you use the proper oil, and enough of it, you should have great luck with R-134a. It will not kill your compressor unless you overcharge, use the wrong oil, use too little oil, etc.

There is a high failure rate when using R134 on a compressor designed for R12. Apparently it has to work a lot harder. I will see if I can find the article.

Also, R134a doesn't cool like R12, especially on a retrofitted system. However, I am putting in Duracool, which works even better than R12.
I was thinking of revamping the AC system in my car... glad I didn't. I decided to pull it (I live in NY, how often do I really need AC?) When I pulled the condenser, the bottom row ripped off with the fitting on the hard line... I was so glad I didn't fill the system after that happened.

Anyway, nice write-up
Charles said:
How much were you charged for the vacuum?

Duracool is illegal in the states, btw. But I ordered anyway. R134A sucks and kills R12 compressors.
I was charged $20 for the vacuum and UV dye.

Duracool is illegal? Really? When did that change? I guess that's why switched over to HC-12 (Hydrocarbon 12) refrigerant recently. It's basically the same stuff as duracool anyways.
Awesome write up, and like Stikershop said, great timing. I did not realize how simple it was to make the conversion. Now I can finally get my small wallet to cough up the dough to fix my A/C (finally!).
Hey, does anyone know the capacity of the stock system. I'm looking to use Duracool, but I don't know how many ounces of the stuff to order.
stickershop said:
Duracool is illegal? Really? When did that change?
I was just reading some info online about this the other day. It's an EPA issue - they don't have enough data to determine if Duracool is safe to use in an R-12 system, so I guess they default to it being illegal. Duracool (HC-12? HC-12a?) apparently has been approved for use in R-134a systems. What exactly it takes to legally convert from R-12 to R-134a I'm not sure... but once you're there, Duracool is perfectly legal.
Isn't bureaucracy great? :?
No, I think Duracool is still illegal in the U.S. It always required swapping to R134a fittings. It is just that they haven't gotten approval from Big Brother and probably won't with all the vested interests. It is still a great refridgerant. Much better than R134a and slightly better than R12. Damn government.
Sorry. My mistake. It IS legal in the U.S. Didn't use to be I thought.
our cars are to be filled with approx 29-34oz of R-12 according to the HELMS.
R-134a requires about 80% of the amount of R-12, so if you're charging with R-134a, you would use 23-27oz of refrigerant.
They come in 12oz cans, so i would use about 2-2.5 cans.
you can use a pressure chart from one of the newer civics to determine when your system is fully charged. Sadly, the new reciever-dryer units from honda don't have a sight glass, so you can't tell when you've cleared it.

I read that duracool uses even less refrigerant than R-134a.. so you can use those figures with the guidelines from the duracool site to figure out how much you need.

djhankb said:
I bought the vacuum pump from harbor freight for about $10.
Just got mine. Thanks for the heads up on that. Now to find time to put in the Duracool...
6 ounces of Duracool = 15 oz R134 = 17 oz R12.

I've got a question though. Does the adapter for the R134 fittings come on the gauges or on the pump? The Harbor Freight down here didn't have a pump. I've got access to a very nice vacuum pump, only problem, no way to hook it up. Another possibility, does anyone know where to pump up fittings for a R134 fitting down to a normal air hose schrader valve?
This is what I got. Comes with the R134a fittings.


Venturi-type vacuum pump removes moisture from air conditioning systems so can you safely add refrigerant. Easy to operate, just connect an air line and it pulls full vacuum within 2 minutes. Ideal for automotive air conditioners, home air conditioners, refrigerators, freezers, and more!

* Includes 1/2" ACME (R134a) connector.
* Vacuum level: 28.3" of mercury at sea level
* Air consumption: 4.2 CFM
* Air inlet: 1/4'' NPT

Overall dimensions: 8-3/8"L X 5"W X 6-1/2"H, Weight: 1.75 lbs.
I actually have a friend whose family has a shop and would vac it for free, but the gas back and forth would have cost almost as much as just buying the pump itself!
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Oh, and I have an email coupon I can send you if you want another $2 off. It would then be $10 plus shipping.
lessonsinspeed said:
Does the adapter for the R134 fittings come on the gauges or on the pump?
The gauge set from Harbor Freight comes with two adapters that go from the R134a quick disconnect fittings to a 1/2" acme fitting. All of the manifold set connections are the same 1/2" acme fitting found on the above venturi vacuum pump - the pump just screws onto the manifold's center hose.
As for the adapters, are you looking for something to go from the stock R12 fittings to the R134a quick disconnects? Or are you trying to find an adapter to use with your vacuum pump?
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