A/C Trouble Confirmation

[elprup87]

I am having some trouble with my A/C system and think my expansion valve may need replacing. Here is some back story:

I had the system evacuated to recycle the old R12 (what was left in it) after noticing a leak around my accumulator. I replaced the accumulator with one from NAPA and did a retrofit to R134A. After vacuum passed, I added freon to the system which went well until I noticed my gauges didnt work (ones I also got from NAPA). My cooling temps were good and I added the right amount of 134a into the system so I decided to unclip the gauges and call it done. I was puzzled about the gauges because I had high pressure readings, but no low side. Sight gauge looked good. I thought just a bad gauge. I went to unclip and somehow the highside gauge damaged the valve. The valve shot out the engine bay along with 134a

I cleaned up the truck and pulled vacuum to start work again. Purchased a better set of gauges and started over. This time my compressor highside readings rise to about 500 then the comp shuts down. Low side readings were about 20psi and I had not added all of the needed 134a into the line. Sight gauge looked normal during adding charge. I stopped and decided to take it to a friend for a second set of eyes. The unit would not cool below 80*

He hooked gauges up and it just looked low to him. He started to add 134a and it started cooling right away, down to sub 40s. Sight glass was normal. He stopped adding after a new ounces and noticed that the gauges were 25/250. The car started to stop cooling again and the pressures were the same. No coolant visible through the sight glass now that we are not charging.

Now we are both a little stumped and I wanted to consult you guys before I start opening the line again. I can stand driving around without A/C, but the boy and the misses dont like it much. Any thoughts?

 

[1972FJ55]

If the expansion valve is going bad, usually you will see the low side go really low or into vacuum. Is it possible that there is still air in the system? Is the heater valve closing all the way? 25/250 are decent readings, so it should be cooling. When it stopped cooling, were the gauges still reading 25/250? Fan clutches are a known problem, but you would see the high-side go way up. These are just some ideas to check, hope they help.

 

[elprup87]

Thanks for the help. I noticed that it wasn't cooling while I was putting the gauges away. However, I noticed later down the road that the A/C light on the dash was not working. Come to find out, the fuse was blown. I am not too sure of the cause at this time, but I replaced the fuse and its working normal now. I will want to look at the readings too see where I am on the list, but its too cool out right now. The temps are blowing 38/40* at a stop.

 

[Flank]

Question about your retrofit: proper retrofits will involve new seals in all joints, new gauge valve fittings (IIRC, this is to make sure that both refrigerants are NOT mixed in a system) and a system flush. R12 and the mineral oil lubricant and R134a and its lubricants are incompatible with each other, which is why a flush is needed. Without a proper flush, the mixture will become corrosive to seals and compressor vanes alike. Improper flush will create a sludge in the system that can eventually damage the compressor, depending on the type. While I admit having no training in the mechanics of how to perform A/C repairs, I did work at my Uncle-in-Law's compressor re manufacturing factory, and saw the aftermath of compressors imploding from improper flush and evacuation of the systems. R134a can also be destructive to the seals used in R12 systems, as they are saturated with the mineral oil lubricant.

Did you change your valve fittings? If not, that could account for the valve damage. Typically, the chemical damage to seals from incompatible lubricants takes a while, but have you tried charging with a leak test dye to see if there is a leak somewhere else in the system?

Just a few ideas. I have no idea of your expertise with AC, or if you just left a lot of stuff out of your explanation of the retrofit, but from what I learned, a proper retrofit (especially in a 15 year old+ vehicle) needs to be dis-assembled and have all system seals between all parts replaced.