My experience with R-134a.

[Dfeland]

I would like to share with all of you what I went through and exactly what I did to convert my truck to R-134a. Just to give some background on myself and those around me my dad is a retired district manager for Chrysler my brother works for the local dodge dealership as tech and I have worked for the state for the last ten years doing commercial heat and air. Before I did the conversion not being very familar with auto a/c's because I don't deal with them much especially conversions. I had heard all the rumors about not cooling as good, smaller molecul,e gel oil, and higher pressures etc. Before I did the conversion I called Sanden compressor corp (who makes our compressors) to find out if our compressors would work. The guy I talked to said yes if fact our compressors would work and to not worry. He also stated to me that at the time R-134a was introduced that they believed a different type of o-ring was required (note I said required not reccomended) becaused they believed at that time the others would fail. He told me that over time that theory was proven untrue it is not neccesary to change the 0-rings. My next two phone calls were to Auto air of Oklahoma and to M. D. Heck corp here is oklahoma. Both of them told me that the hoses would work fine and they do not need to be changed. They also told me that the only reason to change the oil in the system was because the R-134a would not adhere to the mineral oil and would not travel thourgh the system to lube the compressor and the compressor would fail within a year if not changed out. My air quit because the pop-off of the back of the compressor blew due to high head pressure caused by a faulty fan clutch. Otherwise it would still have r-12 in it. When I did the conversion I had to pull the system apart to put a new expansion valve and blow off. I had to pull the compressor to drain the oil while I was there I went ahead and put new o-rings and yes they were green. I flushed the system with mineral spirts and blew out with an air gun. I put a new expansion valve which is the exact same one as R-12 and a new dryer. The dessicant in the dryers are different meaning the R-12 dryer will release the moisture it has trapped using R-134a. But I was told that a R-134a dryer will work for R-12. After all this I put the system back together and pulled a deep vacuum for about an hour. Checked for leaks and pulled again for another 30mins. So far I have only added 24oz of R-134a and I consistently get 50 degree air from the vent. The coldest I ever got from the R-12 was 55 and yes my expansion valve was probably bad. The book calls for 38oz of R-12 and everyone told me that you use 80% for R-134a so I think it will probably need more but I am just seeing how things are going to work first. Oh and just for FYI our compressor call for 135cc of PAG 100wt which I believe is around 4-5oz. Overall I am very happy with this conversion it beats going out and paying $20 for 12oz of R-12 and my initial impression is it is going to work just fine. I am not suggesting that everybody go convert but these are some things I found out while doing mine. My pressures at this point 85degrees outside 200psi high and 20psi low. I have not checked superheat or to see that the whole evaporator is saturated. I think that there is room for improvement and will post end result later. Again other experience's may be different from mine and if any info that I was told turns out to be untrue I will post. Now its time to go enjoy the cold.

 

[bgilbert]

Thanks for sharing that info, can't remember but I think its Danny?. I sure am jealous. I've replaced everything in the system cept for the hoses and condensor, my pressures are too high for some reason, the bro in law says theres a blockage or restriction in the condensor and to change it. ?

 

[Dfeland]

The guy at M. D. Heck told me that the hose can sometimes break down and cause blockage or something could be stuck in the condensor. But and this has been my experience as well usually high head is caused by lack of airflow. I would seriously check your fan it should move alot of air at idle. If it does check for cold spots around your dryer and condensor because usually a blockage will freeze up right after it because it acts like a metering device. Good luck hope that helped.

 

[Paychk]

The Dodge TSB on 134A retrofit says to put in 32 oz. or 2 lb. of 134A.

 

[MRickard]

Sounds kind of like there is not really any gain over R-12, and that if the R-12 system is working just fine, than no need to switch. (?)

 

[dan brooks]

Originally posted by MRickard

Sounds kind of like there is not really any gain over R-12, and that if the R-12 system is working just fine, than no need to switch. (?)

That is correct. The advantage of R134 over R12 is the cost: Last time I checked, R12 was around $90 per pound, so if your AC system needs to be fully recharged because of a bad compressor, leak, etc. , it's often cheaper to convert to R134, even with the cost of the new parts figured in.



When I had my F150 done, it was cheaper to install a rebuilt compressor, new dryer, and orfice tube, and convert to R134 than it would have been to just replace the clutch and recharge with R12.

 

[Detroitiron]

I'm a card carrying mobile A/C tech, and Dfeland's experience, and his thoroughness, are the way it should be. ANY system will fail if it's not in good working order. I've done several conversions, and sometimes I have to replace something not known to be bad until I start the job. Vacuum down, check for leaks, vacuum down again, and use a dial-a-charge or a recycling machine. Oh yeah, 32 oz of r-134 should be right for most,if not all, conversions on CTD's. Always use the recommended oil, and don't worry if you use a tiny bit more than called for, a little more won't hurt, because it doesn't flow/lube quite as well as it does w/r-12. You can do most conversions for less that $100. A refill w/r-12 could go over $300-400. Big difference for a bunch of workin' stiffs like us.

 

[John - K5AWO]

Hello DetroitIron



Got a question for you. I bought my truck used six months ago so have no history to refer to. The a/c has been marginal on it thru the winter (Phoenix) but was okay sort of.



Last week we broke the 100 mark earlier than usual. Mildly cool was the best it would do. I added about 10 oz to the a/c system and quit when it started blowing cold air.



However, it isn't working the way it should. My son has the same truck for comparison. His blows 38-39 degree air at idle. Right next to him, mine blows about 70. Ambient about 98 and humidity less than 5%.



In the evening going home from work, temps 100-102, the a/c starts working fairly good blowing about 48F in 35 mph city traffic. About 5 minutes later at the RED light I can never seem to miss (gotta check that lens to see if it's okay, ya know) it starts blowing 75F air. Roughly a mile later (50 mph now) it starts to cool down until it reaches 43F. Best I have ever seen is 41F at 70 mph, on outside air, temps 98 today. I can reduce the blower to the 2nd notch from the top and it drops to 40-41 air.



Coolant temp stays at 195 consistently regardless of load or outside temps.



After dark, it will blow 38F air. I feel it has too much oil in the system. Your opinion?



I have gauges and a vacuum pump but just haven't done anything with it yet. No recovery system at my disposal, so if I do any work on it, it means a new dryer and purging the lines and compressor to get rid of all the old oil, etc...



Oh, one other thing I forgot to mention. About 10 Sq inches of condenser fins have been knocked over by the dealer's wash boy and the high pressure hose. I gotta comb them out, just never got to it.



Tnx for any help...

John

 

[Paychk]

I'm not a mobile HVAC tech, but from the symptoms, comb the fins out and it should start working much better. Truck movement = better A/C, idle = yuck. The heat transfer from the condenser is inhibited unless air flow is really high.

 

[BCaldwell]

My ac ain't working period. But thats beside the point right now. Welcome to the nut house detroitiron.



Bill

 

[Dfeland]

You have to remember that an air conditioner is nothing more than a heat transfer pump. It blows cold air in(evaporator) and blows hot air out(condensor). If either one are blocked or partially blocked you get poor performance. Your a/c should not have to much oil unless someone put it there. Even then if it does have to much oil normally it will get trapped in the condensor. I would first check your pressures and see what they are. If the head is to high you have either a blockage in the condensor or an air restriction. You say that it works going down the road, I would lean towards an air problem, bad fan clutch, air damn missing, bent fins, bugs in the condensor etc. I know this I will not be without A/C and will do whatever it takes to make it work. Have a Happy Day.

 

[Detroitiron]

Hi guys, and thanks for the welcome. I'm right at home in a nuthouse. I'm a Mopar driver for longer than I can remember. (John, you got too many chebbys) Also, Dfeland is right on with his advice. I might add, check the simple stuff first. Like ensuring all the wiring is tight on the connectors and has no breaks which can cause intermittent current delivery. Harbor Freight has a great fin straightener for cheap, get one, it has 5 sizes in 1 tool so it works on most condensers/evaps. Also check function on the vacuum actuators on the blend and recirc doors, under the dash. My shop manual, a DC pub the dealers use, said that at ambient of 100, 70-75 at the center discharge vent is normal, also that 60-70 psi on low side (suction) and 270-330 psi on high (discharge) side is normal at 100 ambient. You could have internal/intermittent system blockage,only way to tell for sure is step by step diagnosis. Hope this helps some, hard to see from VA to AZ.
good luck,
Dave

 

[John - K5AWO]

Thanks guys for the good feedback.



I knew I was going to have to comb out those fins, and with 117+ days in the near term... ... having the best performance I can get out of that a/c unit is imperative.



Last summer, we hit 118 in our parking lot. Asphault temp was 157 read with an IR pistol. Cab temperature was 175 when I got in... jeez marie, I couldn't get any wind in my sails. My asthma kicked in big time. I was nearly home before the a/c could overcome the heat load (18 miles and 25 minutes).



This year, I have a covered parking space. Hope to be able to retain it all year.

 

[Detroitiron]

more info for John-K5AWO

Your bent fins on the condenser are,IMO,something to fix but not critical. Carrier published a tech paper wherein they say that a condenser can suffer a 1/3 surface area reduction and still deliver near peak performance. Dirt/debris on the tubes/fins hinder heat transfer more than bent fins will. I still think you have an internal blockage or very low refrigerant in the system. Possibly a slow leak. My '87 had a receiver/dryer and my '01 has an accumulator,both have internal dessicants that can be saturated and are not serviceable,but replacing them isn't too big a $ bite. I replaced the receiver/dryer when I converted the '87 to R134. Hook up your gauges and see if you have pressures in spec. You might also try a dye check. Airflow over the condenser is critical, as you know you have more cooling when you're moving than when you're idling. I've been known to pedal up the idle at a red light on a really hot humid day here in Southeast VA,just to move some air over the condenser. You have the dry heat,we have all the humidity we can stand,90% is nothing unusual. I know I sort of jumped around from one cause to another, but I'm thinking you might have more than one defect, and I hope this info helped a little. It could be something as simple as a loose fan belt, but I'm hoping you already checked that. Notice I did not say "assumed". I try to assume nothing and check everything. As I said in an earlier post, Dan was very thorough in his post and that's how he got good results. If you want, send me a direct email and I'll try to address specific issues. One more thing,I am a IMAC certified mobile A/C tech, but I don't do it for a living,there are lots of guys that are very knowledgeable and do it every day. Me,I'm a hotshot driver, an o/o,and I like being on the road making that turbo sing.