2010 Jetta TDI cooling fans not running

I have a 2010 Jetta TDI where the cooling fans are not running. The Freon pressure is good. Does the troubleshooting guide : http://pics.tdiclub.com/data/516/A4_Coolant_Fan_testing_Rev_7.pdf also apply to the A5? If not what changes would there be?

MkV MK V MKVI MK VI fans test AC troubleshooting with VCDS

The changes are sweeping in nature.

The fans on the old mk IV manual AC system should start in slow as soon as the AC was asked to turn on, it did not matter if the clutch engaged or not.

The fans on the MkV systems must see AC pressure rise before they come on in the AC mode.

Luckily there are very good troubleshooting aides for the Mk V system built into its controllers - a VCDS is invaluable.

Fans - Go into the Engine Controller, OUTPUT TESTS, and choose the one for fan testing circuit one. This should cycle BOTH fans from off or very low speed to full speed in a periodic cycle.

The fan controller is built into the large fan on these cars. It develops the pulsed power signal that drives both the large fan and the small fan.

There is another test in this module for the AC system, but it is of minimal value. It calls itself AC clutch relay control circuit test, but don't be fooled - your compressor has no clutch. It does test that the ECU can tell your compressor to unload. If you run this test, do so on a warmed car, and watch for the changes in fuel as the compressor is allowed to load and unload. Have the AC on, engine on and warmed, AC demanded full cool.

Then go to the AUTO HVAC controller ADV Measuring values:
Choose
refrigerant pressure
Air-Conditioning Operation information
Compressor Shut-off Requirement
compressor current, specified value
Temperature after evaporator

Look at these closely.
If you have .825 amps or so requested current that is max. The refrigerant pressure should be high, and the temperature after the evaporator should be low - 2 to 4 C or so.

A bar of pressure is roughly 15 psig, so you can do the math ( or go to a units conversion site on line and let it do the math for you) to see if your high pressure sender agrees with your mechanical gauge set.

The compressor shut-off requirement is the status of the interlocks, and can tell you what may be preventing operation. As long as it says "no shut-off signal is present" and your current is high, then the pressure should be high and the temperature after the evaporator is low. If the pressure is low (and you have a good charge in the system) then the RCV is probably bad. Do verify that the compressor is turning, which it must be unless the break-away protective system has broken free.

The most common failure on these cars AC system is the RCV, Refrigerant Control Valve built into the compressor.
Next is probably the fans.
Then the high pressure sensor.

Mk V and VI AC troubleshooting.

AC Compressor Refrigerant Control Valve Make sure you get the proper valve for your compressor.

Thanks for your help it looks like the RCV is bad, now to pull the belly pan and check out the numbers.
Thank's
for the insight
Address 08: Auto HVAC (3C8 907 336 N)
19:46:14
5.6 bar Refrigerant pressure 016
Cooling Air-conditioning operation information 017
Compressor active; no shut-off condition is present Compressor shut-off requirement 018
0.820 A Compressor current; specified value 024
25.7 °C Temperature after evaporator 052

Yes, those are the indications of a bad RCV, in my opinion.
More correctly, perhaps, those are the indication of no compression taking place.
Is the compressor turning? The break away springs are not broken away are they?
If the compressor is turning, and you have a good charge in it, then the most likely failure (by far on this system) is a bad RCV.

Yes the compressor is spinning. Now all I have to do is take the car apart and get the numbers off the compressor to ensure that I get the correct RCV.
Fun Times


Thanks for your help

Outstanding information, Dan!

I also have a 2010 jetta an I followed the diag procedure that is above and in the process of running a log of the values mentioned above in vcds and through doing this I noticed that the ECM is telling the compressor to shut off anytime above about 75% throttle. Which is causing my air to go warm. Any ideas what would cause this?

I know it is designed to shut the compressor off at high loads.
Are you actually seeing the percent of demand that is causing this in a field?
There were some basic settings that you could do on the older cars to calibrate the foot pedal output.

Lets see if we can find some instructions somewhere.
Try turning the key to ON, but not start, then holding the pedal to the floor for 10 seconds, then turning the key to off.

Also look in the engine module basic settings area for a throttle calibration.

While looking at the VCDS screen output for the TPS, slowly operate the pedal to the floor and observe the readings. Maybe still in MVB 010?

What do you see?

ok i did more testing to it and i think the low pressure switch is telling it turn off like it doesnt have enough residual pressure at the high load. My low pressure guage is reading 40 psi at idle and drops as i increase the rpms. which makes me think it is just slightly low on freon and the system cant keep up. <--- im no expert though so please let me know if this sounds right at all. high pressure side is at 175 at idle

I will go try the tps right now though and tell you what i come up with.

But since i havent bought a bently manual for this year car yet can you tell me what the pressures are supposed to be in the a/c system?

They vary with temperature,
but generally speaking 150 to 240 psi on the high side,
25-40 psi on the low side.
There is no "low pressure" switch or sensor on these cars.
What is the temperature after the evaporator reading?
Take the readings with the cabin fan on high speed, and the engine at 2000 rpm, and report what you get.
Does your high side gauge correspond to the bar pressure reading on VCDS? roughly 15 psig per bar
give refrigerant pressure, control current, evaporator temperature, and any low and high gauge readings you can get.

12:39:39
13.8 bar Refrigerant pressure 016
Cooling Air-conditioning operation information 017
Compressor active; no shut-off condition is present Compressor shut-off requirement 018
0.820 A Compressor current; specified value 024
9.7 °C Temperature after evaporator 052
36psi low side and 200psi high side

So your high pressure sensor agrees exactly with your gauge set.
The pressures appear normal, but the evaporator temperature is too high.
The control unit is responding to the high evaporator temperature and requesting full control current.

How long had it been operating? Long enough to cool things down?

How did you think the cooling was? What you are used to?

This car the cooling has never been amazing but considering our summers are 115 degrees it was manageable. yesterday alone when i was doing this i think it was still 102 outside.

when i took those numbers it had been operating for about the last 30 minutes intermittently, i had just come back from the store and the car sat for about 5 minutes until i got out there and ran it again.

the cooling is inadequate now. if you try and accelerate the air blows hot for about 2 minutes and when you add city driving too it will almost never blow cold right now unless you really keep your foot out of driving it.

If it was mine, I would put a new RCV and drier in it. This usually fixes this problem, which is intermittent operation at reduced capacity.

The cost would be on the order of $200 for parts and refrigerant, and it is pretty easy to do. You might check with local shops to see if they would do the procedure for you. They would not guarantee anything, make this clear to them, because you are bringing parts and specifying procedure.

Another alternative, sort of proof of concept, would be to simply pull your existing RCV, remove all but the outermost O-ring seal, then file off some metal from the outside of the valve internals to create an assured bypass path(I could provide a modified valve to anyone who wants to try this), then the compressor would operate at full capacity all the time. The cost of this would be the labor and refrigerant (I would do it quickly and not replace the drier.) This would cause freeze up of the evaporator coils on long trips, but would work wonderfully around town on short trips (say less than a half hour - probably even an hour in dry Las Vegas.) You could drive it this way until you had freezing weather again. This would let you know if the compressor itself, and the temperature control valve (TCV) is good.

There are two mechanical RCV cars around the Southeast doing this at present. We chose to do this based on the service of the car, and the fact that the compressors showed some degradation (discolored oil, metal flakes in one.) They are both freezing the owners out of the cabin here in the humid and hot SE.

Hi Dan, thank you for all your help. I have a question, on the same topic.

OP, I can start a new thread if you prefer...

I have an 06, and the AC is delayed in operation. Sometimes it is a couple minutes, sometimes its 10 minutes, or longer. According to VCDS, my temp at evaporator is 14*C. It cools the car down, but not great. Also, only one of the fans is running. The upper one, by the air box. I believe that is the larger one?

I tried running a fan test with VCDS, but is says that function isnt supported??
Compressor Load ranges from 9.8 NM at idle to 5.1 NM at 2400 Compressor RPMs.
Coolant pressure under the same load is 15.8 bar to 18.6 bar

Any pointers for me please?

Thanks,
Caleb

Edit: Pulled a log via VCDS:

Address 08: Auto HVAC (1K0 820 047 EC)

16:37:38
0.0 Compressor Shut-Off Code
800 /min Engine Speed
0.810 A Compressor Current (actual)
0.810 A Compressor Current (specified)
1000 /min Compressor Speed
8.4 Nm Compressor Load
14.6 bar Coolant Pressure
64.0 % Radiator Fan Activation (actual) big Fan is running fast, nothing out of small fan
64.8 % Radiator Fan Activation (spec.)
73.0°C Coolant Temperature
12.0°C Evaporator Temperature

These symptoms point to a compressor problem (lack of capacity) certainly an RCV problem (maybe only an RCV problem on the compressor) and a non-functional small fan. A sticky RCV usually causes delays and reduced cooling.

If the compressor's oil was clear and amber (not burned black, no metal flakes) and the compressor turned smoothly by hand, I would put in an RCV, drier, new charge with 30 cc of oil and a small fan (or repair the small fan).

Thank you for your response!

How can I check the compressor's oil?

The only way to know for sure is to remove the charge, remove the compressor, open the drain plug on the compressor and pour some out.

Many, many people just assume the compressor is good and go for the replacement RCV. This is easy and quick, and more than 95% of the time, it works fine.

You can get some hint of the oil and compressor status when you pull the old RCV.

pcjr said:

Yes the compressor is spinning. Now all I have to do is take the car apart and get the numbers off the compressor to ensure that I get the correct RCV.
Fun Times
Thanks for your help

Click to expand...

Changing out the RCV today and did the trick Now I get goose bumps coming from the chill from the vents when it is 94 F outside.

Thanks for the assistance Dan..

having similar problems on my 06 jetta tdi-cool air intermittently, then it will go hot. never gets cold. here are my numbers:
compressor actual: .82a
load 9.8 nm
pressure 16.0 bar
fan actual 74% (74.8% spec)
coolant temp 86 c
temp behind condenser 15 c

i was planning on calling polar bear and ordering an RCV. i have a sanden with the snap ring. anything i'm missing/other ideas? thanks for the help.

It does sound as if it needs an RCV.
Generally speaking you should also replace the drier with the RCV, or any work on the system. Certainly every time the system is opened for an appreciable time (12 hours or more.)

Everyone please remember that the RCV simply ports refrigerant to a piston, which positions a wobble plate to increase displacement. Wear or particles on the piston can also cause binding, and the same symptoms as a bad RCV.

So replacing the RCV is not a universal fix.

This is why an AC shop, or other professional, will often replace the compressor, drier, and thermal expansion/control valve.

All that being said, an RCV (and possibly drier) what I would do first.

How hard is the drier to replace and do you have any recommendations for where to get one from?

The drier on the MkV (and VI too, I THINK) require removing the bumper cover. You can get one from anyplace that sells the RCV, in general.
I got one from polarbearinc.com, but have yet to install it, so I am not sure of fit.

any good ideas of a quick cheap place to evac the refrigerant? i heard firestone used to do it for $20, but i called, and not anymore. our local vw shop wants $400 to change the valve. i can buy my own vacuum pump (harbor freight), rent gauges, and buy refrigerant for half that. i just need a place to discharge the freon. seems like someone should do it for cheap/free if they get to keep the refrigerant...thanks.

just to update everybody about what happened, first off I really appreciate all the information on this forum. I replaced the rcv valve ordering it from polar bear. It was a bear to get the old one out. I had to remove the cooling fan to remove the old one and install the new one. after that, it was pretty standard. I use my manifold gauge in vacuum pump to pull a vacuum on the system and then charged it with 18 .5 ounces of freon. Works like a charm! Thanks again.

2010 tdi with replaced RCV has A/C always on!

so strange things are happening... similar to a bunch of other people, my 2010 jetta tdi was not really blowing cold A/C. Or, more precisely, it was taking a long time for it to kick in... it would very slowly get cooler, over the course of 15 minutes or so. But eventually it did get pretty cool.

Anyways, so I took it into my trusted mechanic who told me about replacing the RCV, which he then did. On my way out from the mechanic, I turned on the A/C to feel the cool, and for about 15 minutes it wasn't cool at all. I stopped alongside the road after 10 minutes and checked. The fans were not on and the A/C lineset was not cool at all. So I turned around and took it back.

By the time I got there, the A/C had kicked in and it was cold. So I went back home... now here is the weird part. Since that day, the A/C has been ON non-stop. I have been driving with the fan set to 0 (off), and the A/C light off, doesn't matter, the compressor is doing its thing and the lineset is icing over, and cold air is always coming out...

My mechanic thinks that I need to replace the compressor. He said that likely a shaving went into the RCV and now it is stuck open... any thoughts? I was thinking to myself, what if the RCV was just defective? the new one that we just installed? but I don't know. What do other people think? There is no way to turn off the A/C now!

It does sound as if your RCV is stuck, or perhaps the swash plate that it moves is stuck. The RCV is just one element in the controls.

If you are paying a mechanic to work on it, you would probably be better off replacing the compressor. If you are doing the work yourself, then perhaps try another RCV.

Is there a way to test fan function without a VCDS? I was having similar problems, changed the RCV, and I'm not sure if also having an issue with the fans. Was very happy though when I pulled the RCV and the oil was clean, not burnt. While I was charging the system, the fans did not kick on, and never cycled while I was checking if the system was cooling.

I checked the Fans and they are not running however under the VAG-COM they are working fine

14:01:31
005 Air-conditioning operation information N/A
008 Compressor current specified value 0.820 A
011 Compressor shut-off requirement Compressor active no shut-off condition is present
061 Refrigerant pressure-MUX Kaeltemitteldruck 6.4 bar
090 Temperature after evaporator-MUX Temperatur nach Verdampfer 33.7 °C

Would this indicate the High Pressure Switch is Bad? The compressor never kicks in. In the old days you could jumper the High Pressure Switch to get the compressor to run If so which of the three pins get jumper?