2011 CTS Prem Ed Sedan Climate Control not cooling the aiir

[cadillacmike68]

OK the car has been running fine. About 120,000 miles on it. Never had an AC problem.

We took it from Tampa to Miami last Sun (8 days ago) and I noticed that the AC was not keeping up with the heat load. I shut it off (pressed the snowflake button) for a few minutes, then set it back on Auto and it was a little better but would degrade again. We parked it for a week, literally. This past Sat we drove back and same thing, it gradually lost the ability to keep up with the heat load. Same partial remedy, shut off snowflake button for a few mins and set it back to Auto. Did that several times on the way. It was parked on Sun. Today I took it to a shop. Took about 20-30 mins to get there and the air output was NICE AND COLD all the way. I should have just left it alone. The shop evac'd it (about.85 lbs) checked for leaks - none - and then recharged .92 lbs.

But now I get ONLY WARM air. It's still pretty hot here in mid FL, 88F when I left the shop.

What the hell happened??

The compressor clutch engages when it's on AUTO I can see it. Air comes out - plenty of it, but at ambient temp, 86F or hotter.  Running at speed on the interstate it gets Slightly cooler, but that's only the cooling effect of the air flow in the engine compartment.

Low side reads at or near Zero on the shop's gauge and both of my Gauges. It doesn't seem to want to take any refrigerant either. High side was about 40-50 PSI too low as well.

NOTE when the system is OFF the low side gauge is at 45-50. That's the normal pressure for this temp range. When I set it to AUTO it goes right down to ZERO.

Basically it appears that refrigerant is Not moving through the system. It's charged up, pressing the high side valve lets out refrigerant pretty definitively (I only pressed if for a fraction of a second).

Did something get stuck in a tube, expansion valve or condenser or line and is now blocking refrigerant? Can this be flushed or will the condenser (and perhaps expansion valve orifice tube, etc. need to be replaced?

Was the compressor on the way out and that Evacuation did it in?

Any other ideas? This is the boss lady's car and she is already bitching at me to get her a newer car. She has the newest car of the four already.

[cadillacmike68]

They didn't flush the system yesterday. After they evac'd and determined there were no leaks, they recharged. That's when the low gauge started to read zero and it would only output warm (ambient) air.

The dryer was Not getting cold, and it wasn't last night when I checked with my own gauges.

Now for the fun news.  This morning I went back and turned it on after giving the interior a cleaning, and it's blowing cold air again!!. Soooo, there is Something causing a restriction. The compressor by the way is nice and quiet.

I'm going to see about getting it properly flushed.

["Cadillac Kid" Greg Surfas 15364]

Mike
Doesent that car have an electronic TX valve and isn’t that HFO 1234yf?
Greg Surfas

[cadillacmike68]

Hi Greg, these are still R143a It has the 143a fittings.  I don't know abut a TX valve.

[cadillacmike68]

Hooked up a good set of gauges to it:

Ambient temp 90F+ It's still HOT here!

Low side 40-42 High side 200, so I added about 1/2 LB R143a. 

Low: 45-47, High: 250

I Still think the low side should be a little higher because it was over 90F when I was doing this. The high side is still within the green zone on the gauges.

While driving it cools nicely, but stopped in traffic for a while it slowly cools less effectively. This tells me that the condenser is not Internally free flowing enough (the air movement at speed helps the condensation process), but what would be causing that other than debris.

Debris from what??

["Cadillac Kid" Greg Surfas 15364]

Mike,
Pressures sound a bit high for what is essentially a semi critically charged system.  I would start over with an empty system, new dryer and evacuated down to 28" for a couple of hours.  Then recharge by weight EXACTLY  the charge indicated in your FSM.  Then pressures as well as temperatures will be a bit more meaningful.
Greg Surfas

[cadillacmike68]

These things do not have a receiver dryer. There's an expansion valve.  It was just evac'd two days ago. The pressures are well with the green range on the gauges, especially with the high temps here in FL. It's STILL over 80F right now.

What I'm concerned about is the slow lessening of effectiveness in stopped traffic. Something is causing a sub-optimal flow of refrigerant through the condenser (or another part before the evaporator). The AC subsystem condenser is effectively the same as the radiator. If the refrigerant can't flow through it unimpeded, less of it will condense down and be available for evaporation, which causes the air to not be cooled as much. More air through it will negate that, improving cooling the same as moving the car helps the engine coolant temps stay in range.

["Cadillac Kid" Greg Surfas 15364]

Mike
If it cools sufficiently at higher speeds then the condenser is not clogged internally or at least
That doesn’t seem to be the reason for poor cooling at low speeds. If your radiator fan(s) are working AND there is sufficient oil in the system AND the expansion device is correct and unclogged you might have bad or failing valves in the compressor. The reason to recharge by weight to factory specs is that then you cAn use the diagnosis matrix in the FSM. I have never known them to fail

[cadillacmike68]

Mike
If it cools sufficiently at higher speeds then the condenser is not clogged internally or at least
That doesn’t seem to be the reason for poor cooling at low speeds. If your radiator fan(s) are working AND there is sufficient oil in the system AND the expansion device is correct and unclogged you might have bad or failing valves in the compressor. The reason to recharge by weight to factory specs is that then you cAn use the diagnosis matrix in the FSM. I have never known them to fail

Greg, The cooling effectiveness is most noticeable while stopped. If the valves in the compressor are failing, then they could be shedding debris which from what I understand these cars use the more "modern" condensers which have very small passages. I'd have to see one to be sure. That or talk with my engine re-builder who is ac AC Expert. It's not low on refrigerant. It was 3 days ago, but not now.

I never bought the FSM for these CTSs. It is three volumes and is over $300. I'm going by my knowledge of AC systems, which is quite extensive. And yes a partially blocked condenser will manifest itself with reduced cooling efficiency at lower air flow.

["Cadillac Kid" Greg Surfas 15364]

Mike
You have a lot of electronics tied int your control system. If this were me I would bite the bullet and get the FSM and diagnose the individual systems before you start chasing your tail blindly.
Again that is what I would do.
Greg Surfas

[cadillacmike68]

Mike
You have a lot of electronics tied int your control system. If this were me I would bite the bullet and get the FSM and diagnose the individual systems before you start chasing your tail blindly.
Again that is what I would do.
Greg Surfas

Anyone have one on digits??

["Cadillac Kid" Greg Surfas 15364]

This "looks" promising


https://www.ebay.com/i/174489247114?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=174489247114&targetid=935694487826&device=c&mktype=pla&googleloc=9028074&poi=&campaignid=10459841961&mkgroupid=104612009980&rlsatarget=pla-935694487826&abcId=2146002&merchantid=119106302&gclid=EAIaIQobChMIve-Ptfjk7AIVDNvACh0KzgnbEAQYDCABEgKEz_D_BwE