AC not working properly

I have a 2011 Jetta with 55k miles. It's been really hot in Texas lately, averaging anywhere between 100-105 every day. My AC intermittently gets lukewarm, then gets cold. It doesn't seem to matter if it's at idle at a stop light or going 70 mph. I've switched back & forth between fresh & recirculated air, turned it off/on again, different speeds, etc. Anybody got any ideas?

In comparison, my 2000 F150 (with new AC compressor) gets ice cold, no matter what the temp. Usually I have to turn it down after it cools up the interior.

EDITED TO ADD: I have VCDS, although I just know how to do basic functions.

i know on my brothers 2012 gold tdi the ac could not keep up until he remembered to set it to max ac recirculated setting. then it was fine.

ARGH said:

i know on my brothers 2012 gold tdi the ac could not keep up until he remembered to set it to max ac recirculated setting. then it was fine.

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Done that & just about every other combination. Still not working well.

If it were mine, I would take it to a good local (independent) A/C shop and let them check it. They have the tools and experience to get it right.

Joe_Meehan said:

If it were mine, I would take it to a good local (independent) A/C shop and let them check it. They have the tools and experience to get it right.

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This, Alot of AC shops will do a free or cheap diagnosis. And at least when it comes to A/C it doesnt matter that its a diesel.

A few seconds with a scan tool may help, but I am not 100% certain on that platform where to look for A/C pressures. They dumbed down the HVAC so much on those.

The compressor is most likely bad, the RCV inside specifically.

I just ran the VCDS & got no codes. Now I'm more confused.

It did act a little better today while driving, it was only in the mid 90's today.

When I ran the VCDS with the engine on, both fans were on & it cooled. If I turned the engine off, but ignition switch on, the fans were not running, only the blower motor & it was lukewarm at best.

Well, the engine needs to be running on that car to turn the compressor, and the compressor needs to be working to make pressure in order to turn the fans on.

I am looking into how/if you can read refrigerant pressure via the scan tool. VAG went back to a non-electronic HVAC system on the decontented American Jetta to my understanding, so this data may be somewhere else.

You have VCDS, can you access the "climate control" function at all?

I agree with the other - take it to a AC shop.

I have a 2011 manual transmission and have found that under hard acceleration, the air is not as cold. It is almost as if it is trying to save power to accelerate, It is only noticeable when it is really hot, 100+. Driving normally it is fine and sometimes I have to turn up the heater since it gets too cold in the car!

While we are on the AC... Everytime I start the car, it switches on the AC and Recirc. Is this something I can change?

schoeman said:

I agree with the other - take it to a AC shop.

I have a 2011 manual transmission and have found that under hard acceleration, the air is not as cold. It is almost as if it is trying to save power to accelerate, It is only noticeable when it is really hot, 100+. Driving normally it is fine and sometimes I have to turn up the heater since it gets too cold in the car!

While we are on the AC... Everytime I start the car, it switches on the AC and Recirc. Is this something I can change?

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This is a common issue among people with our car.

If you have the temp all the way cold it is on "MAX" which is automatically on recir. If you turn the knob one click clockwise the recirc goes off.

If you go play with those settings youll see what I mean. Just leave it one knotch off max and it wont come on anymore.

oilhammer said:

Well, the engine needs to be running on that car to turn the compressor, and the compressor needs to be working to make pressure in order to turn the fans on.

I am looking into how/if you can read refrigerant pressure via the scan tool. VAG went back to a non-electronic HVAC system on the decontented American Jetta to my understanding, so this data may be somewhere else.

You have VCDS, can you access the "climate control" function at all?

Click to expand...

Yeah, I did it last night. I got no error codes. Other than that, I wasn't really sure what I was looking at with the numbers, etc. It did look like I was limited in what the VCDS could do with the climate control system. I'll scan it again & see if I can get any other readings.

schoeman said:

I agree with the other - take it to a AC shop.

I have a 2011 manual transmission and have found that under hard acceleration, the air is not as cold. It is almost as if it is trying to save power to accelerate, It is only noticeable when it is really hot, 100+. Driving normally it is fine and sometimes I have to turn up the heater since it gets too cold in the car!

While we are on the AC... Everytime I start the car, it switches on the AC and Recirc. Is this something I can change?

Click to expand...

I notice sometimes at idle mine does the same thing, just kinds blows warm air. Today I don't think it got above 85 and the AC did just fine. Maybe my car just doesn't like the 100+ degree weather.

Did this ever get resolved? I am having similar problems and I havent had these issues in the past with my car.

If you do a search you will find many of these cars(mine) simply needed a RCV. Polar Air out of Florida sells them for $63.00. VW doesn't make them they try to get to purchase a new compressor. My car would be semi cool to no cool and yesterday my guru put in the RCV and it's night and day difference.

Once in a while, though, we've run across the compressor truly is just caput. I just had one this week like that. We stock the RCVs (both kinds) and they are cake to swap, so if I do one and it doesn't fix it no big deal. Compressor isn't very hard to do either.

I had to move the fan out of the way to get and snap pliers prongs into the holes. The rcv is snug in the compressor, and there is nothing to pry against to get it out. Adding a little gas help pop it out. Having a lift would have made it easier.

Is replacing the RCV something that is DIY? Or will i need to get into a shop. I have no issues turning a wrench, however if it requires opening the refridgerant system that is above my skill set

You need to recover the refrigerant to replace it, yes.

Thanks Hammer,

Do you know if i need the bolt kind or snap ring kind. 2011 Jetta TDI.
Found them here. Im going to try and find a shop to get to do the work for me if i take them the part.

http://www.polarbearinc.com/PBPC/Homepage/products_Comp_Valves.html

TIA

Can't tell unless I can look at your car. Right out in the open underneath once the splash shield is removed, easy to tell then. Most TDIs have a Sanden compressor with a snap-ring-in RCV.

Great thanks again, I can read that its a PXE16 but ill need to remove the shield to look at it.

I replaced my rcv and thought I was good. Pressure high and low are in spec. Still have same issue. Driving me nuts. Compressor next?

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Define "in spec".

What does the Cimatic see as compressor command and refrigerant pressure?

Sorry in spec I mean high and low pressure on my gauges we're in range. I think low was 100psi. I can check them again. I don't remember the exact number got a broken tractor taking bigger priority that is down. Would be nice to have some decent AC though. Thank you.

oilhammer said:

Define "in spec".

What does the Cimatic see as compressor command and refrigerant pressure?

Click to expand...

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OK, well there really is no exact specification for pressures, just so you know. There are trends that relate to heat load, that vary depending on ambient temps, air flow across both heat exchangers, and of course compressor demand (which is variable on these). There are charts we used to use, way back when, but even they were largely a graphic interpretation of generality. That is why I do not think anyone uses them anymore... none of the techs I know do.

This is taken directly from the service manual:

"Pressures And Temperatures In Refrigerant Circuit

CAUTION: When performing work on refrigerant circuit, observe all generally applicable safety precautions and pressure vessel regulations.

The pressures and temperatures in refrigerant circuit are dependent on the current operating conditions (e.g. engine RPM, coolant fan stage 1, 2 or 3, engine temperature, A/C compressor on or off) as well as on the effects of ambient influences (e.g. ambient temperature, humidity, requested cooling output).

In vehicles with A/C Compressor Regulator Valve N280, pressure is modified on the low pressure side by the valve.

For this reason, values indicated in the following table are valid only as reference points. They are attained at an engine speed of 1500 to 2000 RPM and an ambient temperature of 20 degrees C after about 20 minutes .

The connections provided for measuring pressure for the manometer battery are located in the vehicle-specific refrigerant circuit.

At 20 degrees C with the engine not running, the pressure in the refrigerant circuit is 4.7 bar ."


... then the next page:

"NOTE: At absolute pressure, 0 bar corresponds to absolute vacuum. Normal ambient pressure (positive pressure) corresponds to 1 bar absolute pressure. 0 pressure corresponds to an absolute pressure of one bar on most pressure gauges (indicated by -1 bar below 0).

Temperature in degrees C Pressure in bar (positive pressure) of R134a
-45 -0.61
-40 -0.49
-35 -0.34
-30 -0.16
-25 0.06
-20 0.32
-15 0.63
-10 1.00
1.43
0 1.92
5 2.49
10 3.13
15 3.90
20 4.70
25 5.63
30 6.70
35 7.83
40 9.10
45 10.54
50 12.11
55 13.83
60 15.72
65 17.79
70 20.05
75 22.52
80 25.21
85 28.14
90 31.34"

So, again, "in spec" is a WIDELY varied thing.

And like all modern cars, especially those with computer controlled variable clutchless compressors, all the inputs need be correct for proper operation, AND the charge level has to be spot on for best results.

I have given up on charging by gauge pressure alone. The variables are too broad to count on. I do hook up the gauges still for a reference though and to introduce freon and vacuum/recycle. If it is a hot day and the gauge reads 100 psi on the low side with the a/c on it is undercharged likely. I would expect 50-55 psi static on a hot day and increase to 125 or more running. The high side will vary widely due to temps, fans, airflow across the condenser, etc.

If undercharged temps will be off as there is not enough gas to do the job. Overcharged will do the same but the pressures will usually spike high. Did you evacuate and purge the air from the system for at least 45 minutes? Air or too much oil in the system ruins efficiency too.

I will start charging the system and watch the line temps closely for clues. Often times on simple recharge it means merely feeling the liquid line from the evaporator. If it is cooling that line will be cold to the touch. As the charge gets closer to perfect the line keeps getting colder, and I watch the vent temps closely too. Feed it freon slowly as it starts to really cool the line and wait a minute or two for the system to stabilize while monitoring vent temps. If all is well the temps will drop to a point and stay there, again many variables as to how cold it gets. If the temps start to rise after a short blast of freon, you have started into overcharge country, stop there.

On really problematic cars I have a tempscan tool that will read line temps accurately. A non contact temp gun is not the same for real diagnosis, trust me on that fact. If the temps read correctly in and out of the condenser and evaporator, you have cooling available and your problem lies elsewhere like blend door issues, missing foam on doors, or cooling fan efficiency, or cooling air leakage around the condenser or a number of things.

From memory, the condenser will have a differential of 50 degrees in/out max. Usually see 30 or so on a efficient system with good airflow an fans. Evaporator in/out temp differential is 0 plus or minus 5 degrees. Yes, right out of the evaporator they are near equal. Sometimes it is hard to get a reading right at the outlets of the evaporator or condenser, so I don't go there unless problems force me to.

Usually a careful slow recharge or top up is sufficient paying close attention to all facts like fans, airflow temps etc.

OK thanks OilHammer and pdq. I had a vacuum for 30+ mins and held at -28psi on low side for easy 45 mins. Was sure to not lose vacuum ie didn't accidentally open a valve or anything like that. I'll try adding more refrigerant. I hate those cans. Some of those cans get tapped but nothing comes out. Such a waste of money. I'll check it out again here and report back ;-)

FWIW, I just had this problem last month on my 2015.

Took it to Mike Hevner. Turned out my fan went. All is fine again ...

Still acting weird. Think pump on way out. High side pressure jumls all over the place and e gone bogs down then smooths out then bogs down again. Probably time for new pump?

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