cxxm

Just posting this for information based on my experience.

I have read about 100 different ways to do air conditioning, so this is the road I went down. I am not an ac expert. Just telling what I have read and what I have done whether it is right or wrong.

First it took me a while to get it into my head that the Firebird R4 /CCOT AC systems are not like cars of today. I have yet to meet anyone’s who’s ac system is not flat in their Firebird. I have a 1989 Dodge that is still blowing cold R-12 ac done from the factory.

I have read about two types of ac systems. Those that cycle based off pressure or based off temperature. Those that cycle off temperature use a Thermal Expansion Valve, while the pressure ones use a pressure switch.

The Firebird R4/CCOT AC system is a pressure based cycling system.

I did a retrofit on a 1990 Pathfinder from R12 to R134a seven years ago. I used one of those retrofit kits and did not flush the system. It is still running strong. I believe that system uses a Thermal Expansion Valve. I did replace the drier/accumulator and o-rings. I pulled the system down with a vacuum pump and charged it up with R134a until it was blowing cold. It was a slam-dunk. There was nothing unusual about the compressor cycling. It would run for a bit and then turn off. Never really noticed if it was on or off. Things just ran smooth.

Now the Firebird system has been kicking my butt. I did a retro fit last year from R-12 to R134a . I changed all the o-rings, new accumulator/drier and orifice tube. It ran, but it was cycling every three seconds and jerking the car every time the compressor engaged. Constantly on and off. I did find a bad leak out the high pressure switch in the compressor. Long story short it was toward the end of summer, so I just gave up till the next year.

I forgot to mention I did not flush the system. Everyone has their own opinions about flushing the ac system. Here is why I did not do it. I live in a dry climate. The ac system did not fail due to some catastrophic failure putting a bunch of contaminates in the system. I just replace the above items, pulled down the system and put some R134a in until it was blowing cold. The only problem was it was cycling like crazy.

Oils: The R-12 system uses 525 viscosity mineral oil according to the factory service manual. I have read that the mineral oil will not combine and move through the system with R-134a. It will find a low spot in the system, stay there and not cause any problems. The retrofit kits are 14oz cans containing 12 oz of R134a and 2oz of Polyester oil. I have read that Polyester oil combines with R134a and the mineral oil to move around the ac system. I have read that new cars use PAG oil and that it works great with R134a moving around the system. However, I have read that you should not combine PAG oil and the mineral oil. That the two together make a bad combination and eat things up. Not sure if it true, but why else would they sell Polyester oil with the retrofit kit cans. Since I did not flush the system and still have mineral oil in it, I went the Polyester oil route. Also, I heard PAG oil is corrosive like brake fluid. Anyway I bought an 8oz bottle of A/C PRO R-134a Ester Refrigerant Oil with ICE 32 (Medium Viscosity) (Part 765-3510). I think it was $10. From what I understand it is pretty similar to the mineral oil viscosity.

Please note that I have read things that completely disagree with everything I just wrote. Sooner or later you have to make a choice on what to do.

The factory service manual says the following:

R-12 CHARGING CAPACITIES
F Model …………1362 ml, (48 fluid oz., 3.00 lbs)
(The 420 ml (14 fl.oz.) disposable can of R-12 refrigerant is equivalent to .88lbs)

R-4 COMPRESSOR SYSTEM – Requires 180ml (6 fluid ounces) of 525 viscosity refrigerant oil.

The dictionary says 1 pound = 16 oz

I have read that R134a is heavier than R-12. The retrofit kit says to use 85% of system capacity. So here are the new numbers:

48 fl.oz x .85 = 40.8 fl oz R134a.
6 fl.oz x .85 = 5.1 fl.oz oil

I have read that the more oil you use the less space you have for the R134a, but nothing about any damage it will cause by having excess oil in the system.

At this point, I am not sure how much R-12 oil is left in the system, I put in 5 oz of Polyester oil along with roughly 30oz of R134a last year from the retrofit cans. The system was blowing around 60 degrees, but cycling like crazy.

This year: 5/10/13

Already replaced from last year: o-rings, accumulator, and orifice tube.
I know I have at least 5oz of Polyester oil and who knows how much mineral oil in system. I read that the compressor does not have a sump and maybe holds a ½ fl oz. The evaporator and accumulator hold the most oil.

I did buy a brand new ac compressor (Part MRY 58229) from O’reillys for $180. Made by an outfit out of Texas. They give very little instructions on how to get your ac working.

I put 2oz of the A/C PRO R-134a Ester Refrigerant Oil with ICE 32 (Medium Viscosity) inside the compressor and spun it by hand many times.

At this point, I figure I should have plenty of oil in the system. As my reasons stated above I chose not to flush the system. I installed the ac compressor, pulled a vacuum, put some R134a and found I did not have any power to the compressor. It took me awhile, but here is what I found out.

1984 Firebird does not have an A/C relay. It took me hours to figure this out. The Pressure cycling switch located on the accumulator controls power to the compressor. When you move the lever over inside the car to ac, it provides power to the pressure cycling switch (along as there is proper pressure in system), which then goes to the compressor. I had no power from switch to compressor. Therefore bad pressure switch. Also, any time you move the lever inside the car to ac, it will turn on your radiator fan and the throttle idle kicker solenoid on the carburetor.

I was using the original R12 pressure switch. I got a new R134a pressure switch from Napa Auto (Part 207883, $20.98). I charged the system with some R134a. Long story short the new switch was bad. When I put the R134a in I heard the switch pop. It was giving power to the compressor all the time. Even if the system had no pressure. It was making the compressor run all the time. The compressor got very hot to the touch. We are talking burning your hand hot. Not good. I got another new pressure switch. Before I put any R134a in the system, I made sure there was no power to the compressor to make sure the switch was working not sending power to the compressor while system was flat.

I put in about 30 oz of R134a until the system was blowing cold (high 50 degrees) out the vents.

Pressure Switch Information:

Low Side (Pressure Cycling Switch on Accumulator): I got this from other folks and saw pretty similar numbers with gauges.
- 25 psi (opens)
- 46 psi (closes)

High Side (Pressure switch in compressor)
- 430 psi +/- 20 psi (closes) according to factory service manual.

At first inside the garage, I put in about 30 oz of R134a until the system was blowing cold (high 50 degrees) out the vents. It was cycling, but no real set pattern. Car 1000-1500 rpms. Eventually, the compressor just stayed on. Constant 30-35 psi on low side and 150-200 psi on high side, no compressor cycling.

Going down the road the compressor was cycling every 3 seconds. 49-50 degrees out the vents.

Pulled back into the garage, held car at 2500 rpms. No cycling. Low side 35 psi and falling very slowly. High side was 250 psi and trying to climb, but very slowly.

I let the car cool down and took a static pressure test. The gauge said 75 psi, when system was cold and R134a was equalized through out system.

The temperature outside that day was in the high 80’s.

Took a break….

5/18/13:

The temperature outside was high 60’s.

Static pressure test. 70 psi. Not sure if I am losing R134a or lower due to temperature change. I might have used a different gauge the previous day.

Cold start in garage.

Low side: 25 psi open, 45 psi closing
High side: 100 psi to 150 psi as low side pressure switch opens and closes.

System was cycling up and down about every three seconds.

Added more R134a. I must be around the required 40.8 fl oz of R134a. The factory manual describes putting in the R-12, by measuring the weight. At any rate you are going to need 4 12 fl oz cans of R134a. Walmart was the cheapest at around $10 a can. Also, it is a lot easier to add R134a when the engine is cold.

Temperature out the vents was low 40 degrees.

After the engine was hot:

Low side: 25-45 psi
High side: 200-250 psi

Cycling down the road at 50 mph:

Compressor on: 4-6 seconds.
Compressor off: 7-8 seconds.

Temperature out the vents was low 40’s at its coldest and high 40’s at its warmest.

The compressor was warm, but not hot to the touch like I described before. In fact I was surprised how cool it was.

I read on another post that the systems cycles every 7 seconds. What I did was hook up a LED light to the power side of the compressor. I then had someone else drive and I counted the seconds as the compressor went on and off. At an idle the compressor stays on longer and cycling pattern changes as rpms change. I would say at 50mph it was pretty consistent with the above cycling.

The key is definitely the right pressure even if it is blowing cold out the vents. The cycling is not like other cars and I would say cycles a lot more than what I am use to, but much better than every three seconds. I am still not sure if I got it right, but its cold going down the road. The factory manual talks nothing about the compressor cycling time that I could find.

Lastly, here are some references I found to be helpful:

Technical Article on retrofitting to R134a.
https://www.thirdgen.org/retrofitac

Youtube Video: How to Recharge an AC System – EricTheCarGuy

Information about ac oils:
http://www.e38.org/pparish/oil.htm

Someone’s post about (oil capacity on R4 compressor)
http://acsource.net/acforum/viewtopic.php?f=1&t=1409

4 Seasons: Manufacturer of my new compressor advice.
http://www.4s.com/upload/Four%20Seas...ty%20Parts.pdf

I will post some follow up information when I know more. Good luck….

Reid Fleming

iTrader: (2)

I applaud you for your detailed research and work put into this.

1) What state are you in? Ambient temp and humidity make a big difference. 80° weather is pretty easy for monitoring pressures in the system. 60° is very difficult.

2) 25 psi is too high of a cycle off pressure for an R-134a system. Most people run it around 22 psi. I like 20-22 psi depending on where you live. Hot south? Go for 20. Northern state? 22 is fine. But 25 is too high. Turning the screw in the low pressure switch by 90° to the left = 8 psi reduction. So turn it 45° and you should be in the ballpark of lower 20's cycle off psi.

3) Some people recommend 85% charge. Some people recommend 90% charge for R-134a conversions. Are you removing a hose from the low pressure port every time you change a can out? Are you losing a lot of refrigerant while doing this? My yellow charging hose has a **** that seals the hose from leakage. This prevents A LOT of refrigerant from leaking out while swapping cans.

4) What size orifice tube did you use? Many people swap out the white GM 0.072 model for the blue Ford 0.067 orifice. What people don't know is that a smaller orifice tube requires more refrigerant. Combine that with potential losses of refrigerant while changing cans and it can make a car seem properly charged by can size. But in reality undercharged.

5) That the system is supposed to cycle every 7 seconds is hogwash. A vehicle in Houston, Phoenix, Miami, Vegas will generally not cycle at all during the summer months. The same car in the same cities will cycle quite frequently during milder spring/fall weather.........The ONLY reason our compressors cycle at all is to prevent the system from icing up. That's it. Compressors are designed for continuous operation. That is the preferred route. That's one of the reasons why variable displacement (non cycling) compressors were invented.

In the residential world, homes will have design temperatures of say 95° and 75°. That being that if it's 95° outside, the system should (in theory) run forever and just maintain 75° inside the home. This would be the preferred system both in energy efficiency and equipment lifespan. The reason I mention this is to let the compressor run. Compressors only burn out when they have no oil/too much oil and too little/too much refrigerant. If everything is at the proper amount, they'll last you for a long time.

6) You need more refrigerant. You're close. But not quite enough.

KITT1983

iTrader: (3)

Any updates

cxxm

I have not had a chance to dig back into it yet. I had some other projects get in the way. I should be able to provide an update in a week or two.

hrspwr

iTrader: (3)

From my experience, when the compressor cycles that often it means that there is not enough refrigerant in the system. Adding a bit more usually cures it.

cxxm

Did my best to answer the questions. Sorry for any mistakes and do not mean any disrespect nor looking for any arguments. This is all new to me and just fumbling along based on my experience, right or wrong. I think “time will tell”, will be the deciding factor here.

Answers to questions:
1) I am in the Boise, Idaho area. It is considered high desert and very dry.
2) Clarification. The high pressure switch I got from Napa Auto said it was a R134a high pressure switch. The 25-45 psi numbers, I got from one of the many books I have read about auto a/c. Honestly, when I was trying to track it on my a/c gauge set, it seemed pretty close. It was opening and closing pretty fast at the time, so I just went with the numbers from the book in my research. Not disagreeing with what you wrote, just had read something else and went with it.
3) I was using my yellow hose on my gauge set to swap out cans. I do not think I lost very much refrigerant.
4) I got the orifice tube from O’Reillys, part number MRY 38623 for $1.99. It looked like the stock one.
5) In Idaho my house a/c cycles all the time even in very hot weather. The cooler it is the more it cycles. The hotter it is the less it cycles, but once the temperature in the house reaches the set temperature the compressor shuts off. Even in a 100-degree weather, I can hear my neighbors’ a/c units shut on and off when I am sitting in the back yard just like mine does. I am not sure if it has something to do with humidity, but I’ll I know is that when I go from Idaho to a humid climate, I feel twice as hot and cannot work all day like I do in Idaho. I have family in Virginia and the humidity there about kills me. I am not sure how a/c units run in humidity.

So with all that said, I carefully consider everything Reid Fleming wrote about adding more R134a. I also spoke to several mechanics and they thought if it is blowing 40 degrees out the vents leave it alone and the cycling was normal in the 80 degree weather.

I decided to hold off on doing anything until I got into some 90 degree weather.

I went on a road trip to visit some family in California (Los Angeles Area). The weather was above 90 degrees leaving Boise. I was traveling at 75 mph with the A/C running at Max full fan, blowing 40 degrees out the vents. At first it would stay on for around 5 to 10 minutes at a time. Eventually, things got pretty cold inside and it would start cycling the compressor on and off. Not sure of the frequency, because I was driving, but could tell by the LED lights hooked up to the compressor wire. Other than the LED lights, I could not feel the compressor go on and off. I turned the a\c on and off many times to let the car heat up inside to see how long the compressor would stay on before cycling. The amount of time depended how hot the car was inside. I was pretty worried about things, so I was only running the a/c for around 20 minutes at a time for a couple of hours before I no longer needed it.

One day in California, I let my wife drive. We were right next to the ocean, it was humid, not too bad and not like Virginia, the temperature was in the high 80’s. We ran the a/c for about one hour straight. At first the compressor ran non-stop for about 15 minutes, then it started cycling once it started getting cold inside. The compressor would be on for about 10 seconds and off for about 6 seconds. It just did this over and over again. We were running at 70 mph down the highway and did not feel the compressor shut on or off. It was nice and cold inside the car. It was blowing 40 degrees out the vents.

I am guessing it is the ocean air, but the engine felt like it had more power next to the ocean than it does in Idaho in the high 80’s.

Lastly, here are my mpgs for the roughly 920 mile trip to California.

Boise to Twin Falls: 17.7 mpg at 75 mph (had some hills, head winds and turned ac on and off a lot.)
Twin Fall to Ely, Nevada: 20.3 mpg at 70 mph
Ely, Nevada to Las Vegas: 20.6 mpg at 70 mph
Las Vegas to Los Angeles: 21.2 mpg 70 mph (Seems like there were a lot of down hills.)

I was running cruise control for the entire trip.

I am running all stock, including the E4ME carb.

More updates to follow……..

cxxm

Another follow-up….


I ran the ac all summer and it was a great 41 degrees out the vents. Nice and cold...

When it got in the high 90 temps, the pump did not cycle. It stayed on pretty much the whole time. In traffic, which the fan running, the engine temp would run about 230 degree. I normally run the car about 210 degrees, which is what it runs going down the road at speed. If I turn off the ac, the engine temp falls right away.

So to recap, when the outside temp is in the 80’s or lower the ac compressor cycles like I mention above. When the outside temp is in the high 90’s it runs constantly with no cycling.

Even when it does cycle now, I do not notice it jerking the car around when the compressor engages.

It is all working very well and I am very happy with the results.

84'Firebird

iTrader: (1)

How bad of a job was it too do all of this? My 84's compressor is locked up and I'd like to have working a/c next summer. As of right now there is no charge, I'm assume it's from the compressor failing. It looks to have been retrofitted at one point.

KITT1983

iTrader: (3)

Call classic auto air for a kit

http://www.classicautoair.com/OEM-Air-Conditioning.html

Jeffs82TA

iTrader: (1)

I have done 4 a/c systems on 134a based cars and just use my harbor freight vacuum pump and charge and it works great.

R12 I guess has issues when you try to use a 134 with a r12 condensor, the r4 compressor is garbage simple as that.

I did a r12 to 134 on my 90 vette and it did really good, so maybe that r4 compressor is the issue.

97 z28 vacuumed down and held overnight



charge and blowing at around 42 degrees this is where compressor turns on



this is where compressor turns off



air flow over condensor makes a big improvement, That and I notice pressure and cooling differences between a 97 camaro 3.8 and a LT1

The 3.8 keeps its compressor runing all the time the z28 cycles but they both cool the same.

84'Firebird

iTrader: (1)

How much did the pump and gauges set you back?

Jeffs82TA

iTrader: (1)

pump was about 100 gauges about 75 I think. I've don't a total of 5 cars with it and each gets 40 degrees.

Also used the pump to bleed my camaros brakes which it did it extremely fast, has a lot of good uses.

cxxm

It is not a bad job at all, but it can be labor intensive, especially if you decide to pull apart the whole system and flush everything. I took a chance and did not do this. Plus you have the advantage now of everyone's experience, which increases your odds. Mine is still going strong and it was worth the struggle and money to get it going.

KITT1983

iTrader: (3)

I replaced my a/c compressor with stock
A/C compressor replacement & R-134a retrofit kit (accumulator , cycling switch, office tube, r134a coupler fittings, o-rings)from Napa. My a/c still works since 8/2008. My KARR is daily driven.