A/C technical assistance needed.

[nswst8]

I am going to be converting back to R12, so I need alittle advice. The Texas heat has proven to be alittle more unrentant than Florida and Connecticut. And I just passed and received my 609 certificate.

I have nothing against R134a, I've used it since 1997 and it did great. Its just that I can afford the R12 doing all my own a/c work and now I can purshase it legally

Here are my plans: Just replaced the compressor, so remove and completely drain and replace mineral oil.

Replace drier
Replace expansion valve
Replace evaporator
Replace all O-rings
Replace condenser with good junk yard condenser, Known to hold pressure (I already have it)

If I have missed anything let me know about it.

Thanks all.

[system-f]

You might want to pour some A/C flush through the lines while they are disconnected, but other than that you are more than golden with that process.

[DBMaster]

I would go with one of the hydrocarbon refrigerants. I have had the certification since before Freon was banned in 1994 and still have it in my A/C, but if I were having to replace the compressor I would go with something like this.

http://hc12ausa.com/

The reasons are that these types of refrigerants work BETTER than R12. You use less and end up with even lower head pressures than R12. The output temperature will also be colder than R12. Also, since they are compatible with mineral oil you won't have to worry about an oil issue. Even though I have been able to buy R12 over the years it is $35 a can retail and I can't always count on my "Mexican Connection" to get me $2.50 cans from Mexico.

ALL auto air conditioners lose some amount of refrigerant over time. In my case I lose about half a can of Freon per year. It has been that way since the car was new and remained that way after replacing everything in 1999. I think it is better to stick with something that you know you will be able to buy for a reasonable price for the foreseeable future and that does not have the disadvantages of R134a (i.e. high head pressures, requirement of different oil, and poor performance in an R12 system)

[2oodoor]

all that sounds like a helova plan.. except... the used condensor. Why?
That is where the nasty stuff winds up, an unknown condensor would be risky. Also the metel inside condensors can start to distort, causing problems as well.
I would also try some newer style cooling fans.

[nswst8]

Question, I installed a new Denso compressor which I've been running R134a in for about 2 months.

Now if I'm reading correctly its a direct replacement even thru the coupler adapters I have installed for R134a.

Its designed to charge as a liquid thru the low side, won't this hydrolock the compressor?

Have you used this product?

[DBMaster]

Pnem3 (a fellow member) charged his system with a blend of propane and butane. That is also similar to the HC12a stuff. It won't hydrolock the compressor, but I admit that I have not used it. My research and the direct testimony of a Pnem tell me that this is a better way to go. We are talking BETTER performance than with R12. You use only about one third of the amount of refrigerant and you ignore the sight glass (I don't even think driers have them any more). You charge by weight and output temperature.

If you are not feeling adventurous then R12 is definitely a better way to go than R134a. I currently have nine years on my replacement system with R12. It was the Honda kit with the Denso compressor, bracket, drier, and hoses.

Pnem's claim about 37 degree vent air sounds really good, though. I can get 40 in the garage and about 45 on the highway in the summer heat. He was going to post a how-to (possibly) about charging with propane (from a gas grill) and butane (Ronson lighter gas). I would call that the really cheap way to go.

[Oldblueaccord]

I thought I would post this since in some AC post someone ask about vent temps. Old system,junkyard compressor, converted to 134a in 1995 i guess.

August here temp about 93 F humidity was low about 43%. Car sat all day in the sun I left to go do a bar gig about 4pm. AC on high/REC. I let the car run 1 min to get the oil temps up

1st mile I hit one stop light and ran up an entrance ramp to I-40. Came up to 60 mph 4th gear and has a middle vent temp of 70 gegrees. After 3 miles I got to 50f 60-65 in 5th which is 3000 rpm. My whole trip is 30 miles one way. After 20 miles I went down to fan speed 3 since really I felt cold vent temp held at 45-46f. The car felt comfortable after the 3rd mile but I flet relief even after the 2nd mile into the trip.

I don't have guages but I would say high side would be around 200 psi. The compressor does not run the car down engaged. I had just added a can of 134 about a week before. I think it would be a little better at 225 maybe a little more.

I agree mine leaks around the evap I never changed those O rings to much PIA at the time. Cleaning my evap really helped and I don't get the water build up like I used to inside the box.

wp

[nswst8]

Your high side with 134a will average 2.5 X ambient outside temp not to exceed 350 on a 90 degree + day.

I had mine at max pressures 40/350 22-24oz of R134a / 4oz of ester oil. But I had not cleaned the evap at that time.

Had I taken the time to replace the expansion valve o-ring I honestly believe the R134a would have held up. But I had the R12 so I used it.

[nswst8]

Basic Charging Procedures
REFRIGERANT CHARGING PROCEDURE IN AUTOMOTIVE A/C SYSTEMS

We recommend reading this procedure completely before charging. You may need information before charging you want to keep handy. Have this procedure with you while charging. Although it can be done by a single person, we recommend having a helper around.

This procedure outlines the steps to perform a complete charge. These steps are not to be used to refill or make partial charges. Toping off requires system parameters monitoring and knowledge, specially in R134a-based system. Excessive gas will harm your system and will keep it from cooling properly. MORE REFRIGERANT DOES NOT MEAN COLDER TEMPERATURES

CHARGING IN GAS OR LIQUID - Please read step 10

Do not use the sightglass (if so equipped) in R134a-based systems as if were R-12 based.

SPECIAL EQUIPMENT REQUIRED

1) Vacuum pump

2) Gauges (R12 or R134a)

3) Service port adapter (as required in most R12-based systems) R134a systems do not require adapters other than the couplers in your gauges in the majority of applications

4) Refrigerant gas (R12 or R134a)

5) Optional: 2-3 ounces of specified oil.

**************

1. Make sure what is the required amount of gas. From factory, all systems have a decal under the hood that give the data. If the decal is missing or you are not sure, please specify make, model, and the type of refrigerant used and whether your system is a factory or an after market unit here. It is very important to know if your system has oil. Oil starvation is the main reason of compressor failure. Oil can be added to the system in two ways: with oil injectors or through the low side port under vacuum. The procedure to add oil through vacuum is described here. Some refrigerant charge and other useful specifications are provided here.

2. Connect both blue and red gauge hoses to the system's service ports. The discharge port (red hose) is located somewhere between the compressor and expansion device, either before the condenser or after it. In R134a systems, the port is the thicker of both, while in R12 systems is the thinner one. In some aftermarket systems, the port is located in the back of the compressor. If your ports are located in the compressor, the low side is marked by an "S" and the high side by an "H". Port caps have an "L" for low or "H" for high.

3. Open both gauge valves. Connect the common hose (yellow one) to the vacuum pump. Make sure both gauge needles are zeroed down. Needle is adjusted by turning a fine screw inside the dial. You must remove the plastic lens to do this.

4. Turn the pump on. You'll notice that both gauge readings begin to drop. The blue gauge's needle will even dip into negative values. The desired low side reading should be less than -25, while the high side will remain at 0.

5. After approximately 5 minutes, close both gauge valves. Turn the pump off, and observe the needles. Any movement will indicate vacuum loss. The faster the movement, the greater the loss. If after two minutes you don't see any needle movement, open both valves, turn the pump on, and continue vacuum for not less than 30 minutes. Close both valves then turn the pump off.

6. Get ready to charge. Have the necessary refrigerant amount handy. Cans make charging easier and more precise unless you have a charging cylinder or a precision scale.

7. Disconnect the yellow hose from the vacuum pump and connect it to the can tap or charging cylinder valve. You can charge in two ways: liquid (can upside down) or gas. Liquid charging is a lot faster but not recommended unless you extreme care or have experience. Traditional (gas) charging is slower but safer.

8. Once you've decided, and with the can or container connected, unscrew the top yellow hose connection (at the gauges) allowing refrigerant to escape for a couple of seconds. This will purge the air out of the hoses so you make sure that all you dispense is refrigerant. You can do this venting in liquid form so you can see when a fine, steady stream of refrigerant escapes indicating that all the air is gone from the hose. Don't breathe refrigerant and don't charge in a flammable environment.

9. "Flood" the system with liquid refrigerant (can upside down) by opening the red valve (high side) until it won't take anymore. Close the red valve. Jump the low pressure cycling switch (if so equipped). If you don't know what this is or where it is, ask for help here.

10. Turn the engine on. Turn the A/C into MAX on its third or higher blower speed. You'll note that both gauge readings are now positive. The red gauge should read between 100 and 150, while the blue gauge between 5 and 15. If you are charging with cans, don't forget to purge air out the hose after hooking a new can as described in step 8 above. Now, charge will continue through the low (blue) side (see note below) . If you haven't jumpered any switch (you don't have to), you'll notice the compressor cycling frequently on and off. That is normal. The cycling will disappear as you dispense more refrigerant. The only disadvantage of frequent compressor cycling is that charge will take longer. Needles will move up and down with every cycle. This is normal. Do not jump any switch unless you are absolutely certain!.

WARNING: DANGER

NEVER OPEN THE RED VALVE WHILE CHARGING. The red valve is to be opened only during pre-charge, vacuum, or when a system is evacuated. Its function is keeping an eye on the high side only. It must be closed at all times. If you have any doubts, wait until you receive information. Severe injury or death may occur. Remember: ALWAYS wear safety goggles. NEVER charge your system in a closed environment.

GAS OR LIQUID CHARGING?

There are two ways to charge: gas (can or cylinder up), or liquid (can or cylinder upside down). A compressor is designed to compress gas. Direct liquid charge will harm the compressor if suction pressure is not controlled. Liquid charging is faster, yet is riskier. Liquid charging should be made by professionals or under supervision. Liquid charging can be done if the suction port is away from the compressor (some compressors have the suction valve in its body).

Liquid charging can be done never exceeding a 50 PSI suction pressure. If you can't control it, charge in gas form. In cooler weather, cans may freeze. You may immerse them in water and shake them while charging.

11. Once about 2/3 of the charge has been dispensed into the system, spray water in the condenser to optimize heat exchange and speed the process. When you get the condenser wet, vent temperature is likely to raise. This is normal. You'll also note pressure drop in both gauges.

12. Once the specified amount has been dispensed, close the blue valve. Let the system run for a minute. Turn the A/C off and then the engine. Wait another minute and disconnect the couplers from the service ports. Disconnect the low side first. If you jumpered a switch, reconnect it too.

Optimum cooling performance is attained after 10 minutes of operation. Our own acceptance criteria is at least 50°F in the center vent to the driver side at idle after 10 minutes or less. Remember: cooling increases while the vehicle is in motion.

VERY IMPORTANT

Due to the physical properties and chemical composition, R134a and R12 charging amounts are different. Never, if you are retrofitting, charge the same or specified amount of R12 with R134a. If in doubt, please e-mail us here. Do not use this procedure if you are using any other refrigerant. This is just for R12 or R134a. Although procedures and parameters may be similar, we do not use nor recommend alternative refrigerants.

HOW TO DETERMINE OPERATING PRESSURES

Every vehicle has its own operation parameters specification. Depending on whether or not the vehicle has a factory or an after market system, and whether it was retrofitted or is still original, among others. There is no established calculation to determine the exact operating pressures.

The low pressure (blue gauge) should be 35 or less at idle, regardless of the type of gas. Only if you're running a dual system, the low pressure may be between 45 and 50 at idle.

The high pressure, for starters, is directly related to ambient temperature: the higher the temperature, the higher the higher the pressure.

Bear in mind that dispensing a complete charge without lowering the pressures with water will result in higher readings. This is normal, and that is why you should spray water in the condenser at 2/3rds of the charge or once you have completed it. You'll note an immediate pressure drop when you spray water in the condenser.

To obtain a ballpark high side value, multiply ambient temperature by 2.2 if you have an R12 system. If you have a factory R134a system, use 2.3. To convert °C to °F, use this formula: °C X 1.8 + 32.

Remember: this is only a ballpark. If in doubt, we have factory charts to help you determine the correct pressures. Please have your vehicle's make, model, refrigerant type, and year and click here.

Factors like a an obstructed or very dirty radiator and condenser, weak or inoperative fan clutch, weak or inoperative radiator fan(s), either electric or mechanical, will make pressures go up and impair cooling, even in mild days.

[Oldblueaccord]

Yeah I don't have guages or a 30lbs tank. I just use cans and a small hand made hose 134a(can) on one end and r12 on the other(port). I am quite happy with mine and how long it has lasted me.



wp

[nswst8]

This youtube video gives alot of no nonsense advice even charging without gauges

http://www.youtube.com/watch?v=PqNR7PGuE1s