A/C recharge blows very cold at first, but then...

[FSUDAL]

My parents gave me their old 2010 Buick Lacrosse CXL AWD. The a/c blows only a little cold (60 degrees at vent in 75-85 degree weather). I added pure r134a and the temperature dropped to 30 degrees. Thought success! Later that day it was back to 60 degrees at vent. Gave up and took it to repair shop (national chain). The evacuated the system and recharged, checked for leaks, checked pressure, and changed an old Schrader valve on the low side that leaked briefly when disconnecting manifold gauge. Right after it was recharged, once again, blowing nice and cold. Thought success! A day later back to blowing 60 degrees at vent. Drat. Took back to shop first thing in morning. They rechecked pressure, leaks... and said everything was working properly. Of course, it was only about 65 degrees out at the time and blowing close to 40 degrees at vent. Explained that when warmer will not cool that low. Sure enough when it warmed up to 80 degrees I was back to only getting 60 degrees at vent. No real changes when idling in park, driving around town, or on the highway. Shop said I could bring it back when warmer to have them look again. It doesn't seem to be an intermittent problem.

The only clue that I have is it blows nice and cold right after a recharge but then back to 60 degrees at vent in 75-85 degree weather. What do you think could be causing this?

 

[richardnewton]

We have had terrible luck with those DIY AC cans.

It is best to test the AC when in hotter weather, so system is under load. I suppose 75F + would be ideal.

You could have a leak. Your shop should should have put dye into the system so they (and you) to help spot leaks with a UV light. There are gas sniffing tools that the shop may have. And they can measure how much gas evacuates from the system (they know how much went in last week).

Or the AC clutch is not properly engaging. That could be a bad AC clutch, bad wiring, or an issue downstream (e.g. pressure sensor signaling a limit or problem). On a hot day you should see the clutch engaging on the AC (be careful not to get a finger, a tie, or hair caught in the belts!).

Another possibility is that the condenser is clogged with debris (that is outside attached to the engine radiator). That might reduce efficiency of the system (and might stop the clutch from engaging).

Or the outside AC fan is not properly engaging (bad fan, bad wiring, bad relay...).

If the clutch is bad, that can be replaced but the shop typically will just replace the entire compressor/clutch assembly. If you have to buy a new compressor, I would strongly recommend paying extra for an OEM GM part; IMHO the cheap Chinese replacements are noisy, short lived, and do not cool the cabin very well.

 

[FSUDAL]

Thank you so much for taking the time to provide an informative and detailed response. Agree on the DIY refrigerant and temperature comments.

The shop said that they did put dye in when they evaluated and recharged the system. When I brought it back they said they didn't see any leaks and were somehow able to tell that the same amount of refrigerant was still in the system (not sure how they were able to do that without evacuating the system again).

Unfortunately, I have a clutchless compressor. What would be the best way to test it? Would ac manifold gauge pressure check work? They checked pressure at shop and said high/low side pressure was good.

Interesting comment regarding condenser. Is there a way I can check if condenser is working properly? It doesn't look like it is clogged with debris and the cooling is not improving while driving vs. parked and idling.

Both fans come on when I turn on a/c but I don't know if the fans are variable speed or at the proper speed. Shop looked it over and thought it was fine.

I was thinking about asking them to evacuate the system and then I would just replace the compressor, condenser, dryer, expansion valve. My concern is that I would go through all that without it solving the problem.

What would you do in this case?

Thanks again.

 

[richardnewton]

Your AC compressor has a clutch; typically 12v energizes a coil at the pulley.

On a warm day, when you activate the AC button on the dashboard, the clutch should be energized; you should be able to see this activating at the belt pulley. It will not be running all the time.

 

[richardnewton]

Our LaCrosse has powered slats at the grille which restrict air (to improve gas mileage principally). If those slats were stuck, I suppose the condensor might not receive sufficient airflow. I read about a fault code relating to those slats but don't remember where.

Not sure your car would have those powered slats. Or if it would matter.

I would not just throw the parts cannon at the car. Let the tech figure out the problem on a warm day and fix what is broken. This could just be a wiring issue or wonky sensor but a 15 year-old compressor may be on its way out and unable to perform at higher loads.

I am only a DIYer so can't help much more.

 

[FSUDAL]

Your AC compressor has a clutch; typically 12v energizes a coil at the pulley.

On a warm day, when you activate the AC button on the dashboard, the clutch should be energized; you should be able to see this activating at the belt pulley. It will not be running all the time.

Your AC compressor has a clutch; typically 12v energizes a coil at the pulley.

On a warm day, when you activate the AC button on the dashboard, the clutch should be energized; you should be able to see this activating at the belt pulley. It will not be running all the time.

My bad Richard. You are correct. I was mistaken since the front of the compressor is always turning even if the a/c is off. I uploaded a short video of the compressor when the a/c is off to my Microsoft OneDrive account here: Car AC Off.mp4

I checked the GM compressor part which confirms it has a clutch. See part details on RockAuto here: More Information for GM GENUINE 19419918

Should everything always be turning on my a/c compressor even when the a/c is off (auto climate control is also off)?

 

[FSUDAL]

Our LaCrosse has powered slats at the grille which restrict air (to improve gas mileage principally). If those slats were stuck, I suppose the condensor might not receive sufficient airflow. I read about a fault code relating to those slats but don't remember where.

Not sure your car would have those powered slats. Or if it would matter.

I would not just throw the parts cannon at the car. Let the tech figure out the problem on a warm day and fix what is broken. This could just be a wiring issue or wonky sensor but a 15 year-old compressor may be on its way out and unable to perform at higher loads.

I am only a DIYer so can't help much more.

Thanks for the suggestion. I will check on the slats to see if they are there on my car. I do not have any fault codes. I agree that parts cannon should be avoided and hope the shop can eventually figure it out once it gets a little warmer out (80-90 degrees).

 

[ulycyc]

If they are sure the system is charged I would look for issues with the climate control panel module. It suppose to blend ac and heat as requested. If bad you may get more heat blend then ac. Not sure on your model but a scantool van help find the problem. It's cold when you first start and so is the heater core then the ac is warm after.

 

[FSUDAL]

If they are sure the system is charged I would look for issues with the climate control panel module. It suppose to blend ac and heat as requested. If bad you may get more heat blend then ac. Not sure on your model but a scantool van help find the problem. It's cold when you first start and so is the heater core then the ac is warm after.

Good point. I'll have to see if blend is enabled even if I disable auto climate control. If I manually max the AC, fan speed, and recirculate it doesn't help or change anything. I opened the hood on the car while AC was on full blast. The low side off the compressor is only cool and the high side is only warm. In comparison, my other car was very cold and hot. Would that rule out potential climate control issues?

 

[ulycyc]

Could be a clogged Expansion Valve but they should have seen signs when they were servicing with erratic gauge readings.

 

[FSUDAL]

Could be a clogged Expansion Valve but they should have seen signs when they were servicing with erratic gauge readings.

I have an ac manifold gauge set. What should I look for on gauges? I will take it back to shop in about a week when it warms up to around 80 degrees outside but I would like to learn more about this before I go back.

 

[ulycyc]

A simple test is with the gauges on and car at operating temps low side is around 30-50 psi and high side 175-225psi. This can vary a lot so it's not important yet. When you shut the car off the low side should jump up around 25psi fast to around 60-80psi. Then both sides should equalize after about 20 minutes. If not the expansive valve is bad, dirty or frozen from moisture inside. This is all assuming it was evacuated and charged correctly.

 

[FSUDAL]

A simple test is with the gauges on and car at operating temps low side is around 30-50 psi and high side 175-225psi. This can vary a lot so it's not important yet. When you shut the car off the low side should jump up around 25psi fast to around 60-80psi. Then both sides should equalize after about 20 minutes. If not the expansive valve is bad, dirty or frozen from moisture inside. This is all assuming it was evacuated and charged correctly.

Nice! I will give that a try this weekend and let you know how it goes. Thanks for sharing.

 

[FSUDAL]

Update: The cooling fans began to stay on long after car was turned off. Found that cooling fan low speed relay was sticking and replaced it. Fans then both ran high all the time (maybe normal when ac is on). Temp at vent was 43 degrees with outside ambient temp 78 degrees. Static pressure was 80. When ac on low side was 31psi and high side was 130psi. After turning off ac pressures equalized back to static in a short period of time. All seemed to be fixed.

Unfortunately, the next day when I started the car the cooling fans ran on low speed all of the time (like before) and the ac did not cool that great (58 degrees at the vent). I was able to command the cooling fans to high speed with my scan tool and the ac worked much better again. I don't know how to chase down what might be happening. It seems that something is not communicating properly when I turn on the ac (since I believe the fans should start to run on high but continued to run at the same low speed). What do you think I should do at this point? I am going back to the shop on Tuesday but would love to try and learn from this beforehand.

 

[ulycyc]

I would forget about the ac for the moment. Something sounds wrong with the radiator cooling system. Sounds like the car is running hot for the high speed fans to be on. Make sure the thermostat is not sticking and your engine temps are normal.

 

[FSUDAL]

I would forget about the ac for the moment. Something sounds wrong with the radiator cooling system. Sounds like the car is running hot for the high speed fans to be on. Make sure the thermostat is not sticking and your engine temps are normal.

Interesting point. For some reason the fans stopped running on high speed the day after I installed the new cooling fan relay. Now the fans always run on low speed (even after driving on highway for a while with the ac on). My scan tool can check transmission temp but not cooling temp. How can I check if thermostat is sticking and what the engine temp is? I have started the car when it is stone cold, the fans run on low speed, and the ac doesn't cool well. Based on that do you think the radiator cooling system could still be the problem? Thanks for your help.

 

[ulycyc]

All scan tools show engine temps even the cheap ones. It's one of the main parameters. After warm up it should be in the 190-210 deg range. High fan should turn on around 225deg but that can vary

 

[richardnewton]

Your scanner should show water temperature or something similarly named.

Rock Auto indicates your car has a 180*F thermostat but the dealer or other source will be more reliable. IME, the engine might run a bit warmer but temperatures should be pretty consistent once the engine is warmed up (if you are driving a similar route with similar weather conditions).

Thermostats sometimes can fail intermittently, making them sometimes tricky to diagnose.

When installing a thermostat, there is a jiggly bit on the thermostat that needs to be properly aligned. And air bubbles must be purged from the system. The coolant has a limited lifespan.

 

[FSUDAL]

Wow! I have a new scanner and was using the menu button for everything. Pressed different Live Data button and there was a ton of info.

Engine temp was between 207 degrees when accelerating aggressively often and dropped to 187 degrees when parked/idling.

Interestingly, I saw that the intake air temp sensor 2 is reading 32 degrees even though it's 73 degrees outside. I am going to try and find a new sensor and replace it.

How do you think this would impact the cooling fans and/or air conditioning system?

 

[FSUDAL]

Your scanner should show water temperature or something similarly named.

Rock Auto indicates your car has a 180*F thermostat but the dealer or other source will be more reliable. IME, the engine might run a bit warmer but temperatures should be pretty consistent once the engine is warmed up (if you are driving a similar route with similar weather conditions).

Thermostats sometimes can fail intermittently, making them sometimes tricky to diagnose.

When installing a thermostat, there is a jiggly bit on the thermostat that needs to be properly aligned. And air bubbles must be purged from the system. The coolant has a limited lifespan.

Thanks!