OT Another Air Conditioner Problem: Followup

Saturday I posted about an AC problem on my 2013 Silverado. This truck is new to me, so don't know the history of the AC problem. Apparently the previous owner had been having problems, assumed a leak as it has die in it. I had tried adjusting the charge, ended up over charging it.

Today I took the charge out, vacuumed the system for an hour, recharged 25oz by weight per capacity label.

The pressures are now correct, at least they were in the air conditioned shop where it was 75*. The return line is sweaty cold. The compressor is cycling as it should. Time will tell if there is a leak. At this point I don't think there is a leak, never could see anything with the UV light.

Now I think I am back to the original problem. The air is cool, but not cold. It seems "thready", as if warm air is being intermittently blended with the cold. I don't think it is the cycling switch, it is too sudden and irregular. Sometimes it is quite cold, then a second later it is back to just cool. Thinking there is something up with the blend door or the actuator. Maybe something has fallen down the defrost and is jamming it, something loose, something broken...

It will go through all the motions, dash, floor, defrost, hot, cold. Just something is not quite right. But for now it's working better, I'll dive into it another day. Any ideas? Typical problems with this model?

Thanks for the help!
Steve

Steve
I have been following your post and am having the same trouble with the service van I drive. It's a 2009 1 ton Chevy. Has worked good until this summer. I know the charge hasn't been added to i have been driving the truck since it had 80 miles on the clock. I'm an HVAC guy and sort of ashamed to say vehicle AC is not my deal. I'm used to big building stuff, chillers boilers heat pumps etc.
Anyways. I'm going back to basics and am going to clean my coils and check if I have a cabin air filter. I made a wand to clean the condenser coil using copper tube with holes drilled in the side of it to slide between the radiator and AC condenser. I'm going to wash it out and start with clean coils this is a very common problem in the commercial AC world I guess I will try to see if it applies to vehicle AC too. Sorry for the ramlbe it's been hot here in PA and my brain has been on alot of other AC problem jobs the van is getting to the top of the thinking about it list lol. I will post and let you know how it works.

try pinching of the heater return hose and see if the air gets cold .

I had somewhat the same problem. one of the vacuum operated doors, either wasn't opening or closing on max air. i'd have cool air and then not have it as condenser froze up. started running AC cool adjustment off max air and just on normal AC air. problem went away and works good to this day.

GM has used orifice tubes but I don't know for sure if they have them on that model. If they do that is classic orifice tube problem. Usually the tube screen collects debris from somewhere in the system and it affects the air conditioning as you describe.

The cabin air filter plays a very big part. I bought my 2001 Silverado brand new. I was disappointed from the first day with how the AC and the heater worked. Just simply didn't do a very good job. Decided that is just how it is and lived with it for a few years. The we had that first warm day one spring where the AC was really needed, but it just barely cooled the cab at all. Got home, started looking for that air filter, found it and pulled it out. It was filthy. I left it out, started the truck, turned on the AC, and it WORKED!!. In fact it had NEVER worked that good. Not even when brand new. I tossed that filter in the trash. 10 years later all is well. Never did replace that filter.

(quoted from post at 09:11:26 08/02/16)
The cabin air filter plays a very big part. I bought my 2001 Silverado brand new. I was disappointed from the first day with how the AC and the heater worked. Just simply didn't do a very good job. Decided that is just how it is and lived with it for a few years. The we had that first warm day one spring where the AC was really needed, but it just barely cooled the cab at all. Got home, started looking for that air filter, found it and pulled it out. It was filthy. I left it out, started the truck, turned on the AC, and it WORKED!!. In fact it had NEVER worked that good. Not even when brand new. I tossed that filter in the trash. 10 years later all is well. Never did replace that filter.

Click to expand...

here is filter & how do I get to it?

(quoted from post at 08:30:33 08/02/16)

(quoted from post at 09:11:26 08/02/16)
The cabin air filter plays a very big part. I bought my 2001 Silverado brand new. I was disappointed from the first day with how the AC and the heater worked. Just simply didn't do a very good job. Decided that is just how it is and lived with it for a few years. The we had that first warm day one spring where the AC was really needed, but it just barely cooled the cab at all. Got home, started looking for that air filter, found it and pulled it out. It was filthy. I left it out, started the truck, turned on the AC, and it WORKED!!. In fact it had NEVER worked that good. Not even when brand new. I tossed that filter in the trash. 10 years later all is well. Never did replace that filter.

Click to expand...

here is filter & how do I get to it?

Click to expand...

On mine, there is a door, held on with 2 screws, on the bottom of the plenum, right above your passengers left foot. Remove those 2 screws, the door comes off, and the air filter is right there. Just pull it out.

Not all of'em are fitted for a cabin air filter, you will have to look and see. You will need a 7MM and 5.5mm socket and driver. The filters (2) are directional.

https://www.google.com/?ion=1&espv=2#q=2001 silverado 2500hd cabin air filter

One of the nice upgrades and why in the ell did they not use it on all of'em :twisted:

Pinch off heater return line with vice grip, see if that changes it

(quoted from post at 10:06:09 08/02/16)
One of the nice upgrades and why in the ell did they not use it on all of'em :twisted:

Click to expand...

The filter is too small. Even when new and clean, it won't flow enough air. Why in 'ell didn't they redesign the whole system instead of just cutting a hole and sticking a filter in there?

What you describe is a textbook example of a bad expansion valve. I would bet that your system uses one.
Here are a few facts:
A blend door does not move "back and forth" by itself. It is operated on most modern vehicles with an electronic stepper motor.
An erratic water flow control valve is a slight possibility - BUT, they usually either work or not. Not sometimes. Many modern vehicles also do not use them.
Perhaps not an expansion valve, but a variable orifice valve may also be the problem. I have heard tell of them, but have not worked on one personally.

If you can get hold of a good scanner you can see the counts on the actuators and watch for fully closed and fully open. It will also set a code if the command and actual counts are not meet.

If a blend door is sticking a indicator would be.

Shad-tree approach.

set the temp mode fully cold Shut off the engine let it set for 5 min.
Start it does it blow heat HOT heat before it starts blowing cold air.

Feel the inlet and out at the evaporator do they both feel COLD about the same temp.

Do you have a pressure gauge reading you can post.

I am putting a compressor on a 04 pontiac GP today if it does not COOL I am going to be looking for HELP
It has a variable displacement compressor with a TXV :twisted: