A/C high pressure sensor code after replacement

[12GaugeRage]

So I replaced my G65 high pressure sensor after getting this code from VCDS.

Address 08: Auto HVAC Labels: 8E0-820-043.lbl
Part No: 8E0 820 043 AD
Component: A4 Klimaautomat 1424 
Coding: 00000
Shop #: WSC 63351 
VCID: 6393AE0302425AFFE3F-513C

1 Fault Found:
00819 - High Pressure Sensor (G65) 
30-00 - Open or Short to Plus

I bought a new one from the dealer that was different from the original one in my car. After replacement I cleared the codes and they came back, ECON LED is still stuck on. I took it to a shop to have the system evacuated and recharged. They told me both low and high sides show the same pressure and it's likely a compressor failure. I suspect they don't have any idea what they're talking about because he first mentioned the A/C clutch is spinning so the compressor must have an internal fault, but he didn't mention the sensor, code, or the ECON light and had no idea what they were when I brought them up. As far as I understand the ECON light being on means the compressor is electronically shut off and that explains the high side not building pressure, right? In this thread https://www.audizine.com/forum/showt...positive-short the OP had gotten the wrong sensor from a parts shop, but it looks different than the one I got from the dealership. Mine looks like the one in the photos old guy posted. What should I do at this point? I have a full set of hand tools, a new R134a recharge can, and a VCDS cable. I don't have a set of gauges but don't mind buying one. I looked over the measuring blocks but I don't really know what I'm looking at or what value is within normal range.

Original, brass colored metal:

20190724_105209.jpg

Replacement, stainless steel colored metal:

20190724_101308.jpg

[MoRbiD]

In this recent thread I recommended the OP grab the sections of the service manual for HVAC.
That along w/VCDS will do more to help you get an idea of what's wrong than just having a set of gauges.

I think 8E0959126B is the new part number superseding 8E0959126. That's if you have a 05 B6.

When the ECON light is on, the ac compressor is shut down as you mentioned.

The shop you took the car to was that at the dealer's where you ordered the part.

You need a oscilloscope to read the signal for that sensor.

[12GaugeRage]

It's an '05 3.0 B6. It wasn't the dealer's shop I took it to, it was an independent shop. I don't particularly want to drop the coin on an oscilloscope right now if I can avoid it. Though I guess it's cheaper than replacing the compressor to find out the old one didn't have a problem, and I'm willing to invest in tools before blindly replacing parts.

How long would it take to download all the information from the HVAC section? I don't want to pay for a 24hr sub and find out it will take more time than I have available tonight.

[MoRbiD]

I wouldn't bother w/the O-Scope.

Each section is a PDF file. Heating, Ventilation and Air Conditioning is 4MB and Refrigerant R134a Servicing is 3MB.

Should go very quick even w/a Broadband connection.

[Gin+]

So I replaced my G65 high pressure sensor after getting this code from VCDS.

Code:

Address 08: Auto HVAC Labels: 8E0-820-043.lbl
Part No: 8E0 820 043 AD
Component: A4 Klimaautomat 1424
Coding: 00000
Shop #: WSC 63351
VCID: 6393AE0302425AFFE3F-513C

1 Fault Found:
00819 - High Pressure Sensor (G65)
30-00 - Open or Short to Plus

After replacement I cleared the codes and they came back

What codes came back? If it's the same code, then you still have a sensor/wiring issue to contend with.

[ApexIt]

I recently replaced my high pressure sensor as well. As Gin mentioned, it seems like you still have an issue with the sensor/wiring. It could be possible that the sensor you received was already dead (highly unlikely, but possible). Make sure to inspect the wiring running to the sensor to make sure there are no issues in the wiring loom. Test with a multi-meter to make sure the sensor is getting a signal.

Also, make sure that the connector is properly seated. When I went to plug mine in, the fit was a little more snug than I had anticipated. I made sure to keep pushing until I hear the "click" that these connectors make when seated properly.

[12GaugeRage]

So I got a hold of a multimeter and have some extra time. Do I test the wiring with the car on? I checked the fuse #6 and it looks good. I'm using this video as a guide https://www.youtube.com/watch?v=JXWqWt1qotg, does anyone know what colors each wire is?

[12GaugeRage]

Alright I went out with my multimeter and tested the wiring with the car on. Let me know if I did something wrong, this is my first time testing wiring using a multimeter.

20190803_182635.jpg20190803_182643.jpg

These pictures show the wiring harness on the side that's plugged into the G65 sensor. I'll refer each contact point bottom to top as #1, 2, and 3, #1 is closest to the rounded side.

So with the engine on I tested each contact with both chassis ground and using #3 pin as ground. #3 with the red lead and chassis ground gave no voltage.

#1 pin reads as:

20190803_182934.jpg

#2 pin reads as:

20190803_182946.jpg

I also traced the wiring, it joined with another set of wires and ends at this connector:

20190803_183444.jpg

I unplugged that connector and found this damage, but as far as I can tell it's just the connector housing:

20190803_183509.jpg

I tested these pins for continuity with the other three pins on the G65 side:

20190803_183652.jpg

I got a solid beep from 3 different pins, so it seems the wiring itself is OK.

My question is are these readings the correct ones? The multimeter shows mV instead of V when in autoranging mode. When I manually set the range to 000.0 V it shows 000.1 V for both pins 1 and 2. I plugged the G65 connector back and made sure I got a solid click. ECON light still stays on. I haven't reset the code with VCDS yet, I came back inside to grab my laptop and figured I post this up to see if anyone replies.

[12GaugeRage]

Went back out and plugged in VCDS, it gave back a code I haven't had before:

2 Faults Found:
00716 - Air recirculation Flap Position Motor (V113)
  41-00 - Blocked or No Voltage
00819 - High Pressure Sensor (G65)
  30-00 - Open or Short to Plus

After clearing the codes the G65 code came back right away but the flap position motor didn't. My guess is the code is from when I had the wiring harness unplugged? Here's an imgur album with all the VCDS measuring blocks in the HVAC section, I took them with the fan speed all the way up and temp set to LOW: https://imgur.com/a/dIHDY2S Unfortunately I have no idea what I'm looking at with the measuring blocks.

[12GaugeRage]

Does anyone know what compressor shut-off criteria "4" is? Also, I get the same 33.0 bar Refrigerant circuit pressure reading that 5spdJunkie had in this thread: https://www.audizine.com/forum/showt...m-won-t-charge

[imnuts]

If the G65 code came back immediately after clearing the codes, that means the issue is still present.

Sent from my Pixel 3 XL

[12GaugeRage]

If the G65 code came back immediately after clearing the codes, that means the issue is still present.

Sent from my Pixel 3 XL

I'm aware, that's why I'm trying to diagnose the issue. I replaced the G65 sensor and trying to test the wiring but don't really know what I'm looking at and learning as I go.

From what I gathered 10 mV on both the signal and reference wires are nowhere near what they should be, am I correct? The wires' continuity is intact. What should I be checking next?

[MoRbiD]

This link might help.

[Kevin C]

Similar issue, it was an overcharged system.

If the system is flooded and R134A is in areas that get hot you will get some very high pressure readings.
https://www.audizine.com/forum/showt...or-(G65)-16-10

If the car has sat for a few hours and is completely cold (non running) what do you get for a pressure reading? If you get reading of 33 bar then you definitely have a sensor or wiring issue. A set of gauges on the high side and the low side would be a quick way to confirm the actual system pressure.


With the car hot and just turned off if your really getting 33 bar (480 psi), some part of your AC system that has liquid refrigerant has to be at about 200°F (see chart). Normally lots of parts of the car at at 200°F when running since the motor gets hot. R134A that's in the liquid form will boil, that boiling raises the pressure allowing the refrigerant to condense elsewhere in the system where its cooler. To get 33 bar of pressure some part of your AC system has to be hot and have liquid refrigerant. It also says that the parts of your AC system that are colder are completely flooded with refrigerant.

[12GaugeRage]

I'm pretty sure it's not overfilled, the receipt for the evac and recharge service shows 18 oz of R134a added, or about 510 grams. Spec is 500+-20g

Sent from my SM-G955U using Audizine mobile app

[shurur9]

1. Stupid question, but did you see an o-ring on the connection for the pressure sensor?
2. Don't necessarily bank on the ac not being overcharged. If it was charged to the hilt in a cool workshop, it can be over pressured outside when it is 100 degrees.

This message will self destruct in 10 seconds:
While ac is "running," you can relieve a bit of pressure with a rag and and a small nail head on the valve to see immediately whether the system was overcharged....

[Kevin C]

If the car has sat for a few hours and is completely cold (not running) what do you get for a pressure reading? If you get reading of 33 bar then you definitely have a sensor or wiring issue. A set of gauges on the high side and the low side would be a quick way to confirm the actual system pressure.

[EuroxS4]

It sounds to be like you have a broken wire going to G65. I know my wiring was all brittle and falling apart. Found a brokne wire about 5-10 inches from the connection inside the sheath i had to cut apart.I'm Not saying thats it. But given your dvom measurement and somewhat little knowledge. I would just go do a contiunity test for each pin going to the sensor from the function connection you found. This will rule out any broken wire from junction to sensor connector or any shorts you may have in the wiring.

[EuroxS4]

Does anyone know what compressor shut-off criteria "4" is? Also, I get the same 33.0 bar Refrigerant circuit pressure reading that 5spdJunkie had in this thread: https://www.audizine.com/forum/showt...m-won-t-charge

Criteria 4 is "Fault code stored" shut down of ac system to protect it from execessive pressure.

[12GaugeRage]

It sounds to be like you have a broken wire going to G65. I know my wiring was all brittle and falling apart. Found a brokne wire about 5-10 inches from the connection inside the sheath i had to cut apart.I'm Not saying thats it. But given your dvom measurement and somewhat little knowledge. I would just go do a contiunity test for each pin going to the sensor from the function connection you found. This will rule out any broken wire from junction to sensor connector or any shorts you may have in the wiring.

Yeah I did a continuity test between that junction and the sensor and all three wires came back good, I'll have to test it beyond the junction. I managed to find a pinout diagram for the AC control unit, just gotta find the time. I might run a 5amp fused wire directly from the battery to see if I can get the compressor running.

[jasc23]

Hi, I was reading this thread and have the same issue in my 08 B7 A4, 2.0T Avant, 6MT, 60K miles.
I have traced the wires signal: blue/brown; ref voltage: red/gray to the HVAC module and the brown to ground in the engine bay.
Everything has continuity, and the system reads 6 bar when the car is in ACC power. However, when I start the car, the reading bounces between 6 and 33 bar and the system is then shut-off.
I am stumped. I have tested duty cycle, voltages, changed Fan control module, HVAC module, 3 High Pressure sensors, de-pinned all connectors leading back to HVAC module to be sure they are good. I still have the same issue.
The code I get is 00819; 00:10 Signal Outside range.

I believe the issue you are having is slightly different because you get an open to ground or short. So it could be the HVAC module, which you can pickup for cheap on ebay, then code it, you are good.

In years of working with Audi/VW/Porsche, this is the weirdest issue I've encountered. It hurts because this car is otherwise pristine and I really wanted to enjoy it this summer.