Ran into an issue with the wifey's ride today. Coming home today she called and said the the fan wasn't working right. She said with the fan on high it was barely blowing like it was on low. I suspect that the evaporator may have frozen over. When I got home, I took it for a quick drive and it was working fine. I have noticed lately that it didn't seem like it was blowing as cold as usual, but I don't drive it much so I wasn't sure. Hoping it might just be a tad low on refrigerant.
I hooked up some gauges and this is what I get. 29-low/245-high. This is running at 2000 RPM on max AC with windows open. Ambient is about 92° and center vent temp is about 58°-60°. This is a 1234 system. Based on what I was able to glean from my search, these seem to be acceptable numbers. I read it on the internet so it must be true.
It dawned on me that this thing has a cabin air filter. My tuck doesn't have one so I completely forgot about the darn thing. Anyway, I pulled it out and it was pretty rough. I have no doubt that it was restricting at least some airflow. I hooked up the gauges again after taking it out and the high side pressure came down about 10psi at 2k RPM. At idle I'm sitting at roughly 45/200. Just wanted to throw that out there as well. I do feel like the vent temp should be a little colder though.
Part of the airflow restriction might have been the partially clogged cabin air filter. But if you suspect that the evaporator is icing-up, then it's most likely low on refrigerant.
As a first step, recover the R-1234yf, or have it done, and see how much refrigerant comes out. If the weight of the recovered refrigerant is lower than the weight-of-charge specified on the under-hood A/C decal, then the system has a leak someplace.
A few suggestions: At the condenser due to damage caused by kicked-up road debris; at the evaporator due to gunk accumulation (decomposed leaves, pollen, dirt, etc.) which, when combined with moisture, caused it to corrode-through; and at one or more faulty o-rings.
Another possibility is seepage at the compressor shaft seal due to seasonal losses.
Member – MACS (Mobile Air Climate Systems Association)
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