Loyale93v Posted June 2, 2012 Share Posted June 2, 2012 My 93 Loyale 1.8L has an R-12 A/C system , I was hoping someone one this forum could tell me what the rule of thumb is for diagnosisng the high & low side pressures. I am a auto tech by trade, I have a set of R-12 guages(that i have never used, (they just were giving to me years ago and i have never needed them) any ways the A/C isn't cooling as I thiink it should so I am looking for some Diagnostic help . What are the correct pressures on a 70 degree Day? The guages have RED= High Side BLUE= Low Side YELLOW= Aux ? Recovery Tank? Re-Charge Tank? Can I use the guages with out the YELLOW Line? What do bubbles in the site Glass really mean? Thanks for any help guys-n-gals Quote Link to comment Share on other sites More sharing options...
FlatFourFrenchy Posted June 2, 2012 Share Posted June 2, 2012 On a 70° day high side might be over 200 and low side below 100. I don' have a chart handy. The bubbles usually indicate that system needs a charge. As using gauges, red=highside, blue= lowside, and yellow is for source of charging freon or recovering freon. To check pressures just turn valves closed or the precious freon will dicharge out yellow hose. Quote Link to comment Share on other sites More sharing options...
Loyale93v Posted June 2, 2012 Author Share Posted June 2, 2012 So ...safe to say that if I keep both valves in the closed position, I will not need to use the middle, yellow hose, and sill be able to get an accurate reading, correct? Quote Link to comment Share on other sites More sharing options...
Crazyeights Posted June 2, 2012 Share Posted June 2, 2012 (edited) As I recall good rule of thumb for the pressures on an R12 system are 25-46 PSI low side with the compressor running and (2) x ambient outside temperature + 10 - 15% for the high side, also with the compressor running. Example if it's a 70 degree day with good air flow through the condenser and evaporator cores the high side pressure would be about 155 to 160 PSI. Both low and high side pressures will start to equalize when the compressor shuts off. There are LOTS of variables that will affect the pressures (IE outside ambient temp, CCOT vs Expansion valve type systems, ect) but at least this should give you an idea of what to look for on a working system. BTW - Yes with both valves closed. Edited June 2, 2012 by Crazyeights Quote Link to comment Share on other sites More sharing options...
Loyale93v Posted June 2, 2012 Author Share Posted June 2, 2012 Thank you every one for your info / input. I'll keep you all posted as to my diag and what comes of it. Thanks. Quote Link to comment Share on other sites More sharing options...
presslab Posted June 2, 2012 Share Posted June 2, 2012 (edited) Yes keep both valves on the gauge set closed. The yellow hose hooks to whatever, vacuum pump, evacuator, freon can, etc. Also when measuring pressures keep the engine at fast idle like 1500 RPM, and the interior fan on high. With R12, if there aren't many bubbles in the sight glass (fast idle, A/C on of course) you are probably charged ok. With R134a you can't really use the sight glass. Cold A/C is a wonderful thing. I just got mine working again after my engine swap and it's cold. The A/C systems in the EA82 seem to be a good working setup. I use a hydrocarbon replacement for R12 and it works good, if yours needs a recharge that's a cheaper way to go. http://autorefrigerants.com/co00033.htm Edited June 2, 2012 by presslab Quote Link to comment Share on other sites More sharing options...
987687 Posted June 3, 2012 Share Posted June 3, 2012 After the compressor is off for a minute or two, the high and low pressure should be almost the same. If there's a considerable difference that's BAD. That means one of the tubes or check valves is clogged up. It's a recipe for bad day. I can't say exactly what the pressures should be, as I'm not used to working with r12 systems, but the fundamental idea is the same as r134 systems. And since it deserves repeating, make damn sure the valves are closed when you hook the gauges up to the system. Quote Link to comment Share on other sites More sharing options...
Storydude1 Posted June 3, 2012 Share Posted June 3, 2012 There are many temp/pressure charts. google is your friend. Sight glass is there for a reason. bubbles means the refrigerant is flashing to vapor BERFORe the metering device(in the dryer or evap., depending on system) and making things go all whacky. Foam looking stuff in sight glass=add more refrigerant. Without a solid column of liquid hitting dryer and sight glass, you'll never get cold air out the vents. Here, Ambient of 104*F I shoot for 28-35PSI low side. Below 25PSI gives a saturation temp below freezing and you'll see evap icing and ice on the low side hoses. Icing is where the problem is. Icing on evap=bad orifice tube/metering device. Icing on compressor inlet=bad valving in compressor. Assuming full charge this is. Below 65*, unless you want to do wetbulb tests, you cannot test an AC system by pressure. No heat to remove means nothing is happening and refrigerant is just moving through the system. Need a heat load to move heat. Quote Link to comment Share on other sites More sharing options...
Storydude1 Posted June 3, 2012 Share Posted June 3, 2012 Yes keep both valves on the gauge set closed. The yellow hose hooks to whatever, vacuum pump, evacuator, freon can, etc. Also when measuring pressures keep the engine at fast idle like 1500 RPM, and the interior fan on high. With R12, if there aren't many bubbles in the sight glass (fast idle, A/C on of course) you are probably charged ok. With R134a you can't really use the sight glass. Cold A/C is a wonderful thing. I just got mine working again after my engine swap and it's cold. The A/C systems in the EA82 seem to be a good working setup. I use a hydrocarbon replacement for R12 and it works good, if yours needs a recharge that's a cheaper way to go. http://autorefrigerants.com/co00033.htm You can dump straight propane into your AC system for 2.50 a gallon. EA-12A is mostly propane without an odor agent in it. I just hope one never blows an evap with it running and smokes. Quote Link to comment Share on other sites More sharing options...
presslab Posted June 3, 2012 Share Posted June 3, 2012 You can dump straight propane into your AC system for 2.50 a gallon. EA-12A is mostly propane without an odor agent in it. I just hope one never blows an evap with it running and smokes. The ES-12a hydrocarbon refrigerants are a blend of 80% propane and 20% butane to get the pressures like R12. So while propane will work, it's not quite the same. Also the mercaptan in regular propane might not be so great for the A/C system. I've heard of people running straight propane though. The welding supply store has 70%/30% mix for brazing, maybe it will work too. ES-12a is only $45 for 6 cans so it's really no biggie. I use 2.5 cans to charge mine. Good thing I only smoke when I'm on fire. Quote Link to comment Share on other sites More sharing options...
Crazyeights Posted June 4, 2012 Share Posted June 4, 2012 What about using ester for oil and converting to 134? It has worked for me but I haven't done a lot of them. Quote Link to comment Share on other sites More sharing options...
Storydude1 Posted June 4, 2012 Share Posted June 4, 2012 I did ester and evac, 34PSI lowside, 104* ambient, getting 55* out of the vents at idle, 49 at 65mph. Sight glass is clear until 3000 engine rpm when it flashes due to lack of airflow over condenser. Quote Link to comment Share on other sites More sharing options...
presslab Posted June 4, 2012 Share Posted June 4, 2012 What about using ester for oil and converting to 134? It has worked for me but I haven't done a lot of them. That's not a bad idea as R134a is readily available. I tried R134a for a while but I get better cooling with ES-12a. In any case I'd say use ester oil, it's just easier and doesn't absorb moisture like single end-capped PAG. Ester oil is compatible with any refrigerant. With mineral oil (as normally used with R12) and R134a, the mineral oil is not miscible and won't lubricate the system. So if using R134a, it's a really good idea to flush the system to try and get as much old mineral oil out as possible. Then add the ester oil, vacuum it down, and charge it up. If any mineral oil is left in the system it's not the end of the world. It will just pool up in low areas, and will diminish the cooling a little. But the key here is to add a full charge of ester oil when converting to R134a. Quote Link to comment Share on other sites More sharing options...
Crazyeights Posted June 4, 2012 Share Posted June 4, 2012 Sweet, thanks for the tips! Quote Link to comment Share on other sites More sharing options...
Loyale93v Posted June 4, 2012 Author Share Posted June 4, 2012 [Original Poster] Thanks for the info guys. It's all good stuff. I am a little weary about using Propane/Butane in my nieces car...Leak + Spark = BOOM I dont know I'll need more info on that. Unless the amount of lubricating oil being carried by the gas charge is enough to differ the combustibility ...if that makes any sense , let me know. {it sure sounded good though} Quote Link to comment Share on other sites More sharing options...
987687 Posted June 4, 2012 Share Posted June 4, 2012 The main problem with the mixture of propane, butane, etc. Is that if you get a leak in the system, the gases will escape at different rates. Meaning you can't just top the system up. It will be an imbalance of gases. Having the system leak and explode is kind of a silly worry. How often have you seen an AC system leak fast enough for that to be possible? It's usually a tiny little leak that lets all the refrigerant out over the course of months. That's not enough to cause an explosion. Also, as has been mentioned, propane isn't really that flammable, just a small leak will not catch on fire. If you're worried about propane leaks, and a fire starting with a mere 20-30 oz of fluid in the system, I advise not putting 15 gallons of gas in your gas tank. And yes, the fuel lines DO run though the entire length of the inside of the car. Quote Link to comment Share on other sites More sharing options...
Storydude1 Posted June 4, 2012 Share Posted June 4, 2012 Big difference between propane and gasoline is propane vapor temp is WAAAY under what Gasoline is. Gasoline at 85* ambient will flash to vapor over time..Propane at 85* ambient is already a gas. Now, Propane is an approved refrigerant in many chiller systems. Any gas that can be compressed to a liquid will work as a refrigerant. My problem with EA-12 is that it is not approved to use in an R12 system in the USA. And without using the proper fittings and labels, if you take that vehicle to a repair shop and do not have labels and fittings, the guy will contaminate his entire recovery tank if he reclaims the EA-12, thinking it's R-12. Sure, he should use an gas checker first, but many shops go by fittings and labels alone. 3Oz of EA-12 makes an entire tank of recovered R-12 useless. But, regarding EPA laws...It's perfectly legal for your system to vent to the air and be refilled every year...But if the Tech working on it cracks a valve seat without being hooked to a system, he is liable for a 15,000 dollar fine. Figure that one out. Quote Link to comment Share on other sites More sharing options...
987687 Posted June 4, 2012 Share Posted June 4, 2012 So put a big sticker somewhere obvious that says what you did. Or just don't take your car to a shop to have it worked on. Quote Link to comment Share on other sites More sharing options...
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