DenLors Car AC Repair Articles – Keep Your Cool
April 25, 2011 7:36 am Air Conditioning
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© DenLorsTools.com Summary: Repair information for automotive AC (Air Conditioning) systems. Hot AC can be a very frustrating thing to deal with, we at DenLors have answers and tools to repair car AC the right way!
Auto AC Repair Articles
1. Basic Car AC Gauge Set Hook-Up
2. Adding Freon to Car AC – Gauge Readings Explained
Ron S. :
Date: June 18, 2011 @ 8:12 pm
Saturday, June 18, 2011
I think your web auto air conditioner info is excellent and helps many folks out. Sorry for the long explanation of my problem but maybe the history will help.
I have an 87 Nissan using Freon 12. The system has been relatively trouble free until recently. I had 10 good years out of it then the dryer desiccant broke up and plugged the expansion valve. I flushed the lines, installed a new expansion valve and dryer, and had no problems for another 13 years. Freon was slightly low in 2006 and I topped it off with R-12. It worked fine until about a year ago, then Freon was low. I recently leaked checked it with a good Yellow Jacket AccuProbe ll and the only leak I could find was on the service caps. Tightening them seemed to fix the leak problem.
Current symptoms were signs of low Freon. It would cool as normal (38 – 42 deg F) on low setting with high RPM but when the RPM dropped or using a higher fan speed, the temperature would rise up. Sight glass showed bubbles all the time, indicating a low charge. The book says there should be no bubbles at idle or high RPM.
The only Freon 12 I had left was a can purchased in Mexico in the late 90’s. The can was marked Freon 12 “Dicloro Difluro Metanoâ€. It has “DuPont†on the label with some Spanish indicating Mexico origin. I put that can in the system and immediately lost the performance I had before with the low charge. The system ran about 20 degrees hotter putting out around 60 degrees F instead of 38 to 42. The slight glass has some bubbles at low RPM but shows solid liquid at higher RPM (2000). (Still signs that it is slightly under charged). The static pressure is (both sides) 108 psi. The pressures are running, vehicle cold at idle – Low – 45 psi, High – 195 psi. At 2000 RPM, vehicle cold = Low 35 psi; high – 250 psi. After vehicle warmed up idle – Low – 49; High 195. At 2000 RPM Low – 32, High – 230. Outside air temperature was around 100 F (Arizona). These pressures are close to the book spec so I don’t think anything changed with the expansion valve and I think it means the compressor is pumping normally.
Please give me your opinion if you have heard of anything like this with Freon 12 from Mexico?
My diagnosis is that I think something is wrong with this Freon. Is it possibly it was recycled Freon 12 that was full of oil or mixed with something else? Would an excessive oil charge cause the performance loss like I have? Or could it be something other then Freon 12 (like mixed with Freon 22)? It looks like I’m going to have to recover the Freon and flush out the system but I welcome your suggestions before I proceed. If you think it may be excessive oil how can I test for that and is there a way to measure for the correct amount of oil without taking the compressor off?
I’m afraid to do the conversion to R 134 because I hear the performance will not be as good as the original with Freon 12. Here in Arizona you cannot tolerate a system not working at its peak. What is your opinion on converting to R 134? Thanks for your help.
dennisb - Auto Tool Sales :
Date: June 19, 2011 @ 7:17 am
Ron, the Freon 12 (Dichlorodifluoromethane) shouldn’t really be the problem. It’s just R12 labled differently from Mexico, as you already know the USA discontinued the production of R12 in 1994. I learned long ago to NOT rely on the sight glass to determine the level of charge (not dependable). Since you say the dessicant bag came apart, I would suspect a partially blocked condenser. When the dryer is mounted near the condenser, it’s more likely that the desicant can contaminate the condenser if it comes apart. The tiny tubes in the condenser may be restricted some making it less efficient. Flushing may help, however it may not. Replacing the condenser may be necessary if it’s determined that it’s blocked partially. I would convert to 134A as a last resort, the compressor should be replaced if converting, since it’s the only component that the old mineral oil will not be able to be removed from by flushing. Good Luck.
Ron S. :
Date: June 20, 2011 @ 7:42 pm
Thanks Dennis,
The desiccant bag came apart in 1997 and after that repair it worked well until now so I don’t think there is contamination in the condenser. The expansion valve should be the first to plug up if the desiccant failed again and since the high and low pressures seem to be in spec I think that is working. If you run the blower on low and let the temp get down the compressor starts to cycle off-on normally so it appears the expansion valve closes down the flow as it gets real cold. Assuming the Mexican Freon was okay what else could cause a loss of performance when adding it? Could it be overcharged and still show bubbles in the sight glass at idle. Maybe I didn’t have a slow leak and its something else. Should I try pressure washing the condenser first? Should I recover the amount of Freon of the Mexican can and see if it goes back to the way it was?
I ordered an o-ring set and new dryer and am prepared to take the whole system apart and flush it out if need be. Thanks again for your help.
dennisb - Auto Tool Sales :
Date: June 20, 2011 @ 8:00 pm
Yes, it could be overcharged and still show bubbles. You could try spraying water on the condenser as a test. Good Luck.
Randy :
Date: July 21, 2011 @ 1:24 am
the R12 you added was probably “wet”, the descant gets saturated over time and low quality R12 contains a lot of moisture which will make it worse. Your description sounds exactly like a saturated system and adding any moisture when the extra can was added will cause what you describe. evac and Recharge with a new Reciever dryer.- 20 years master Tech w/MACS and Imaca certifications.