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68 DVC, 96 FLTWD Brgm, 11 CTS Premium (two)
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Discussion Starter #1 (Edited)
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.

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.
 

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68 DVC, 96 FLTWD Brgm, 11 CTS Premium (two)
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Discussion Starter #2
I'm thinking that Evacuation got something stuck, possibly in the condenser.
 

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2011 CTS Coupe Premium
Orlando - We take orphans
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Older GM cars are famous for the hot/cold diverter valve getting stuck. Key is whether the dryer is getting cold. Did they flush and recharge the lubricant ?
ps GM spec for the refrigerant charge is 1.2 lb of R134a.
 

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68 DVC, 96 FLTWD Brgm, 11 CTS Premium (two)
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Discussion Starter #4
No they didn't flush. 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.
 

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2011 CTS Coupe FE3, 2003 Thunderbird, Gone 2013 ATS, 02 Deville
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What is high side pressure?
You should have pressure on the high side and low side when the car is running with the AC on.
Does a radiator fan turn on when the AC is running?
 

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Discussion Starter #6 (Edited)
Yes the fans come on. I'll put the gauges on it again.

Low side is only reading 40-42. I returned my high side set too cumbersome to set up. I'm getting another set today.
 

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2011 CTS Coupe Premium
Orlando - We take orphans
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40-42F is not bad, 40-42 psi is a little high but static (AC off) should be 70-90 psi depeming on the ambient and under 50 psi on the low side should be cooling. Is the dryer getting cold ? Are you sure the dash air is coming from the AC and not the heater (common problem) ?

ps going to a shop may be a fast way to spend a large.
 

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Discussion Starter #8 (Edited)
Down here the low side should be about 50-55 with the 85-90 deg temps. I am getting another set of low and high side gauges and will check it tomorrow. When the system is OFF the low side pressure is at 75-85.
 

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Discussion Starter #10
OK, with the good gauges and outside at 90F+ (it still HOT here):

System OFF low 70-90 This is normal.

System on AUTO and temp set at 60 (max cool): Low 40-42. High: 200

Put in about 7oz of R134a: Low: 45 or so. 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??
 

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Discussion Starter #12
It sounds like they are, but I didn't look. Engine temp does NOT creep up in traffic. I'll check them tomorrow.
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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When stopped try putting in Neutral and raise the idle to about 1200. What happens ?
Agree, but when the car was on the highway at speed then there should have been plenty of cooling through the radiator(s) whether the fan(s) worked or not. Therefore the A/C should have been blowing cool.
 

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Discussion Starter #15
Agree, but when the car was on the highway at speed then there should have been plenty of cooling through the radiator(s) whether the fan(s) worked or not. Therefore the A/C should have been blowing cool.
As I noted above:

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.

It's fine going down the road. but stopped, it slowly cools less effectively.

You can have 100MPH winds going through the condenser and radiator but if the condenser is blocked internally it will NOT cool the air.

The engine coolant temp DOES NOT CREEP UP when the car is stopped. The fans are working. Otherwise I'd have overheated it a half dozen times this week.
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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I know a couple of guys on this forum who are a few ounces low.
 
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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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I'm constantly topping off, usually 12-16 oz at a time.
Proper maintenance is underrated. You are a shining example!
 

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Go ahead, blame me. Everybody does 🙄
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Proper maintenance is underrated. You are a shining example!
I'm guilty of overfilling the reservoir quite often though.
 
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