ok now doing all that and taking those considerations. what is coming out of your center vents? 60* ? theory is great until it is put into practice. theoretically it should probably be 45* in practice its closer to 60.

 

One that affects pretty much all older full size GM's (and other brands as well) are the fresh air inlet door and the blend doors which are both inside the ducting inside the dash have foam seals that break down over the years and simply do not seal as well. This allows a small amount of fresh air to always come in and the blend doors will always allow a small amount of the hot air from across the heater core to get mixed in. Still seems like 60 is a bit excessively warm though. Another thing to always be sure of an AC is blowing warmer is that it is not overcharged with too much refrigerant - that will also make them blow warmer (a tad low will usually actually make one blow even colder).

 

what's coming out your center vents if you don't mind me asking.
with enough responses of actual temps maybe we can debunk the 60* lore.

 

Humidity at 20% is funny to me. I live in the south. I've ran various pressure and temp checks at 65-75% humidity generally, I want to say 80-85F ambient. I don't have the numbers in front of me, but I did take humidity into consideration by looking at a R134A pressure chart that took into account temperature (measured in front of the condenser, not from the weather channel) and humidity. It will cool slightly lower than 60 if I rev up and hold it to 2k RPMs, with or without a fan blowing on the condenser, but not as cool as driving at 45MPH+.

I didn't find any metal pieces in the orifice tube and with deciding that it was the clutch that went out, I didn't replace (or flush) my condenser. I did clean the outside of it with coil cleaner with it still in the Hummer. Based on the inlet and outlet temps to and from the condenser, I don't (think) a condenser clog is my issue.

How do you check the blend door for complete functionality? Heat gives off heat and cool gives off cool and that's all I know.

 

I saw an old post I think from you where you installed a cabin air filter. But you had a lot of leaf debris once you removed the blower motor or cut the hole for the filter. If that was your post, do you think a clog in this area could be affecting temperatures any? I'm always pulling out pine straw from those vents by the windshield so who knows how much gunk has made it down there on mine.

 

It works by recirculating the cool air you get from your A/C when you first turn it on. The longer it's on for, the cooler your vehicle will get! If you don't use it, the car will use the air from the outside that is a lot warmer, and your A/C will work harder and continuously to cool the hot air.

 

Yes that was me that posted about adding a cabin filter slot. Relatively easy to remove the blow motor and fan - that leaves a fairly large hole that you can reach up in there and feel around for debris.

As far as checking the blend door seals - not really a viable thing to do. Removing the entire air ducting assembly is a massive project that requires removing the entire dash structure and those blend doors are inside of it. There is also on an aged vehicle, particularly ones that do not have a cabin air filter, quite high odds that the actual evaporator and heater cores (which basically look and work like little radiators) are also covered in a nice thick coating of dirt from years of usage. When I did cut the slot for the cabin filter that did allow me to actually see the one core and it was visibly quite dirty but still no easy way to try and clean it. At first there was a LOT of leaves and whatnot built up along the bottom of it. I used a long round tube brush to rake the leaves and junk out and I actually did spray some AC condenser cleaner spray up into the slot on the side I could get to and brushed it more and then let it dry. I cannot however say if it really made any difference in temperatures. But I did feel better knowing I got all that crap out of there and had a functional cabin filter after.

I did find one other picture. This was just after I cut the slot and had not cleaned anything out yet. The flat part going up inside on the left is the AC evap core and you can see all the crud on it along the bottom.

 

i have a mac, a/c temp probe in my air vents on both of our Hummers, the H3 stays at 35 degs at night and usually around 40-45 in the heat of of the day, after the interior cools off, the H2 does about the same, the difference in the H2 is when the temperature on the mirror gets scrambled at first start up, the a/c will cool to 60 degrees untill the mirror starts providing the ambient air temperature, then it starts cooling down to 35-40 degrees…..the probs have been replaced several times and wires checked, it just takes about 20 minutes and when the mirror temp starts reading the outside temperature it starts cooling the truck….

 

Can you elaborate on this? What do you mean by scrambled? I wouldn't ever say my mirror is "scrambled" but it definitely seems to read a lot higher ambient than true ambient.

 

what year is the H2 with the scrambled ambient temp?