A5 Air Conditioning thread

[artificer]

I have a problem with my AC, and have the "00819 - High Pressure Sensor (G65) 009 - Open or Short to Ground" fault code.

I did the "Engine module OUTPUT TESTS", and the fans turn. During the AC compressor clutch test it said I had 20.5bar of pressure.

I tried doing the output test for the HVAC, but it said conditions weren't met to allow it or something to that effect. Laptop battery died then, so I have to recharge it or run an extension cord to re-try it. Another thing that bothers me is that I had several can't make connection errors when in the HVAC section. How often do you normally see these?

Whats the next step? Any ideas of what I can try before just dropping $100 on the pressure sensor?

Thanks

Michael

 

[DanG144]

The connection errors do not happen too frequently.

Perhaps the connection errors and the high sensor reading are because of a bad electrical connection or ground?

20.5 bar is 300 psig, and is pretty high, refrigerant saturation temperature about 160 degrees F.

Will the DTC reset and stay clear?

Spray it down with a garden hose, or check it first thing in the morning and note the pressure reading and the ambient temperature - before starting the car.

 

[artificer]

Ok, its morning, and I tried getting the information with a cold (very) car.

I go into HVAC Measuring Blocks, Group 003, and coolant pressure is "-" when the car is off. I can run the HVAC output test with the car off, but not on. When on, it gives me "Requirements for Output Test not met."

In the Engine Output Test, AC compressor clutch, the pressure reads 20.13 bars.

I guess the smart thing to do is to just spend the money on the high pressure sensor, and hope the intermittent connection to the ACCM doesn't mean I need one of those as well. I need to figure out how to access the ACCM/climatic module so I can check the wires for mouse damage.

Michael

 

[artificer]

Spent the money and picked up the High Pressure Sensor. Installed it, and I have AC. Should be back to normal, since it went from working fine to not working, and now working again with the new sensor.

If anyone wants some photos, I can post them. For me the easiest way to replace the sensor was to remove the plastic bumper cover. Then I removed the screw and 2 nuts holding the windshield washer reservoir on, and moved it out of the way. 17mm open end wrench, and the sensor came off. New o-ring, and put everything back together. Not too bad of a job.

Fired up Vag-com, and pressure is 10.2bars. Temp behind evaporator was 2degC, so nice cold air coming out.

Michael

 

[DanG144]

Good job.

Still having communicaton issues?

 

[artificer]

Don't know about the communications. I didn't run the AC or vag-com very long. Does not having sattelite on the radio count? The other day the radio defaulted to FM. I hit the sat button, but it said sat wasn't available. Had to do this a half dozen times, then it worked. Does this use the same module? (climatic?)

Everything seems to be working, so I'm a happy camper.

Michael

 

[DanG144]

No, it does not use the same control module as the Climatic.

However it does tie to the CAN bus. I am woefully ignorant on CAN bus operation, but it seems likely that any single module with communication section issues could foul up communication with other good modules.

Have you done an AutoScan to find all the error codes trapped by all the modules on your car? Saving an AutoScan output file is a very good thing to do for several reasons.

 

[Clark20ry]

Ok I am going to get in on this. I have noticed lately the AC does not start cooling for several minutes after it has been turned off. It blows really cold when cruising down the freeway at 65. then its gets only cool when I am in traffic or at a light. I checked today 102* ambient temp outside and only the large fan was working after I got home. Anyone know where to get a deal on replacement fan?

 

[pawel]

Spent the money and picked up the High Pressure Sensor. Installed it, and I have AC. Should be back to normal, since it went from working fine to not working, and now working again with the new sensor.

If anyone wants some photos, I can post them. For me the easiest way to replace the sensor was to remove the plastic bumper cover. Then I removed the screw and 2 nuts holding the windshield washer reservoir on, and moved it out of the way. 17mm open end wrench, and the sensor came off. New o-ring, and put everything back together. Not too bad of a job.

Fired up Vag-com, and pressure is 10.2bars. Temp behind evaporator was 2degC, so nice cold air coming out.

Michael

Photos would be nice...

 

[pawel]

Today I took a short drive, 20 mi on freeway and observed the values in HVAC, measuring blocks, block number 3. The pressure was between 13.8 to 16.8 bar (200 psi, 244 psi) and fan speed in percentage varied between 72% to 62% specified and 34% to 30% actual, respectively. The both fan speeds in %, specified and actual, went down with increased speed. Basically, the actual fan speed in % was half of specified. Should I be concerned with this? Reason why I did this today was that vent air got "warmer"... when new, the center vent air temperature was around 20 deg F (I have air vent thermometer placed in center vent) while driving freeway speeds for some time. Now, it only gets around 40 deg F. Both observations are based on 68k miles and hot temps, 90 to 100 deg F outside temps.

 

[DanG144]

This is not normal. Usually the specified and actual fan speeds are within a few percent of each other.
It sounds as if the fan controller (mounted on the large fan) may be faulty.

 

[TonyJetta]

Dan,
Are you sure about this...My read was that he was at freeway/open road speeds, when reading fan speeds. In this case, I would think air through the radiator at freeway speeds would turn the fans faster than requested.

pawel,
What is fan requested v. actual, when at a stop?

Tony

 

[DanG144]

Tony,
His actual speeds were lower than his requested speeds, by about a factor of 2, not faster.

I have seen the graphs. I have seen data from other Climatic systems. His is not normal.
Dan

 

[TonyJetta]

Tony,
His actual speeds were lower than his requested speeds, by about a factor of 2, not faster.

I have seen the graphs. I have seen data from other Climatic systems. His is not normal.
Dan

Ok...Thanks for setting me straight. I just reread it...

Tony

 

[pawel]

Dan,
Are you sure about this...My read was that he was at freeway/open road speeds, when reading fan speeds. In this case, I would think air through the radiator at freeway speeds would turn the fans faster than requested.

pawel,
What is fan requested v. actual, when at a stop?

Tony

Tony, there is no difference in reading between requested vs actual while moving or at a full stop. Data that I recorded indicates that actual values were always half of the requested ones.

 

[TonyJetta]

pawel,
Thanks for clarifying.

Tony

 

[Marauderer]

A/C Broke

I have an 06 Jetta with the Climatic sys. Car has 85K mi on it.

Symptoms: A/C does not blow cold air.

Tested at 91*F With gauges hooked up. fan on hi air was blowing at 71*F. Compressor discharge pressure 375 psi.

I figure the compressor is disintegrating and the strainer/orifice is clogged with debris and not moving any freon.

All suggestions and comments are appreciated.

 

[TonyJetta]

Marauderer,
Hi side is about 150 psi too high. What is the low side pressure?

Do BOTH cooling fans come on when the AC is turned on?

BTW..this is an expansion valve system.

Tony

 

[Marauderer]

Thanks Tony.

No orifice a good old TXV.
I don't remember what the low side was. I will check with my friend that was working with me and see if he remembers.

And I didn't check if both cooling fans came on. Both cooling fans that blow across the condenser or the evaporator??

As you can see I am not overly knowledgeable on the A5 system

 

[Marauderer]

And yes I knew the discharge pressure was way to high. Maybe just the TXV or a fan problem.

I will check it out today if possible.

Can I use my VAGCOM to help check this out???

 

[TonyJetta]

Can I use my VAGCOM to help check this out???

There should be tests that VCDS can perform on the cooling fans, and it is capable of monitoring the refrigerant pressure. IIRC, that was discussed earlier in this thread.

Both cooling fans that blow across the condenser or the evaporator??

The cooling fans that blow across the radiator & condensor.

There is only 1 fan that blows across the evaporator, in the cabin.

As you can see I am not overly knowledgeable on the A5 system

No worries...that's what the TDI club is all about...learning and keeping these cars going as long as possible!

Tony

 

[DanG144]

Good call on Marauder's issue. The fans are the first things to check.
You can do an engine OUTPUT test in VCDS, it checks the condensor fan operation.
You can check discharge pressure on VCDS, and should, to verify that the high pressure sensor is seeing actual pressure. You cannot read suction pressure, but you can read evaporator temperature.
You can also read condensor fan speeds, actual and requested, on vcds. Both fans should always run together at the same speed.

These systems normally run at just over 200psi on the high side. By the time you see about 250 psig on the high side you should essentially have full fan speed.

 

[Marauderer]

I will read those parameters and post my results sometime today.

So, if the fans are not operating does the compressor continue to run and that causes the high discharge pressure?? I am concerned about running the system with the high side pressure at 375 psi. I don't want to blow a hose or is that not a concern?

 

[TonyJetta]

So, if the fans are not operating does the compressor continue to run and that causes the high discharge pressure??

Yup....The fans should be running.

What's supposed to be happening in the condenser:
1) The compressor has raised the pressure and temperature of the freon.
2) The air flow across the condenser cools the freon, to liquefy it, by the time the freon leaves the condenser.
3) If the freon has not liquefied, it will still be at high pressure.
3) When the liquid reaches the expansion valve, the valve control the amount of liquid passed into the evaporator, where the evaporator, essentially evaporates the freon back into a gas.

I am concerned about running the system with the high side pressure at 375 psi. I don't want to blow a hose or is that not a concern?

It is a concern...but AC hoses are designed for high pressure.

Just don't run it all day like that. Run it for a few minutes of testing.

Tony

 

[Marauderer]

Thanks Tony and I am very familiar with the A/C cycle. You do a great job off breaking it down for someone who doesn't know it. I just have to find my VagCom and get it hooked up and find the right area to look in.

 

[DanG144]

Fuse SA1, 200 amp metal strip, feeds SA3 50 amp red fuse. These should be on the front face (vertical) of your fuse block in the engine compartment. This is the motive power feed to your fans. Wire #1, 6.0 mm, red.

Fuse SA1, 200 amp metal strip also feeds J317 (main power relay ), one set of output terminals from J317 feeds fuse SB24, 10 amp (on the top horizontal face of your engine compartment fuse panel.) This goes through a wiring connection (A99), This is control power feed to your fans. Wire #2, 0.75mm, black. J317 (main power relay) is probably located on the top horizontal face of your engine fuse panel, and has a 458 painted on it.

There is also a main ground 642 from your fan controller that must be made up. Wire #4, 6.0 mm, brown. This goes to a ground connection "Engine Compartment, on top of left front chassis member". There are also two nearby grounds under the left headlight that should not be confused with this. Quote is from the Bentley.

The last of the 4 wires from your fan control module (located on back of main fan) is a communication wire to the ECU. This is wire #3, .75mm, green.

 

[TonyJetta]

Well, now I have a symptom to add to the mix...Wife called to tell me the AC in the jetta is non-op, and the outside temperature display is three bars.

So, I scanned the car, and found the following:
-------------------------------------------------------------------------------
Address 02: Auto Trans Labels: 02E-300-0xx.lbl
Part No SW: 02E 300 042 H HW: 02E 927 770 AD
Component: GSG DSG 070 0913
Revision: 04007000 Serial number: 00000504200553
Coding: 0000020
Shop #: WSC 00066 000 00000
VCID: 18347C1452E1

1 Fault Found:
18250 - Please check DTC Memory of Instrument Cluster
P1842 - 000 - -
-------------------------------------------------------------------------------
Address 08: Auto HVAC Labels: 1K0-820-047.lbl
Part No: 1K0 820 047 DK
Component: Climatic PQ35 090 0505
Shop #: WSC 00000 000 00000
VCID: 70E464B41AD1

1 Fault Found:
01317 - Control Module in Instrument Cluster (J285)
013 - Check DTC Memory
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Address 17: Instruments Labels: 1K0-920-xxx-17.lbl
Part No: 1K0 920 952 D
Component: KOMBIINSTRUMENT 3HL 1212
Coding: 0023203
Shop #: WSC 00066 000 00000
VCID: 2B5EB3D8F377

1 Fault Found:
00779 - Outside Air Temp Sensor (G17)
010 - Open or Short to Plus

-------------------------------------------------------------------------------
So, I checked some readings:
Monday,27,September,2010,20:15:49:11634
VCDS Version: Release 10.6.1
Data version: 20100831

20:15:30
8.0 Code for Compressor off
800 /min Engine Speed
00:10 Standing Time
0.000 A Compressor Current (actual)
0.000 A Compressor Current (specified)
0 /min Compressor Rotations
0.0 Nm Compressor Load
13.8 bar Coolant Pressure
37.0°C Interior Temperature

So...correct me if I'm wrong, but it appears that without the ambient temp sensor, the AC shuts down.

So, I am thinking that I have a broken wire in that circuit, at an accessible spot, where rats can get to it. Yes, I said RATS. We live on the outskirts of the city and have trouble with roadants.

Any other options or opinions?

TIA!

Tony

 

[DanG144]

Tony,
That sounds like an excellent probable cause - the rodents.
But I would not have thought the HVAC computer would have shutdown for a simple loss of outside temperature sensor.

It would, however definitely prevent operation.
code 8=
8 = Compressor off (outside temperature was less than 1.5°C and is still less than 2.5 °C)

 

[TonyJetta]

Now that I think about it, my B4 has an ambient temp sensor to prevent AC operation when it's too cold outside...so, It does make sense that they use the ambient temp sensor to interlock the AC system.

However, it is unfortunate, that they couldn't be be bothered to write the software to have a fallback mode, to read the interior temperature. Notice my previous post measured it at 37C=98F!

Tony

 

[TonyJetta]

OK...searched bently, to no avail.

I would appreciate any help in pointing me to the right location for G17.

Tony