dicktheslice

I have a 2005 A8 3.0 TDI
The aircon will not blow cold air
I have scanned the car and it comes up with a fault code G65 sensor open or short to plus.
I have replaced this sensor and had the car regassed but it still comes up with the same fault. When I tested it by running a test in section 08 HVAC The compress starts and stops and I get readings of expected results and the pipes in the engine bay to the compress get cold.
Any help would be appreciated as I am now at my wits end and have already spent £200 trying to sort this

maxandtara

Post the following:

• test results of 08 hvac ?
• Low pressure ?
• High pressure ?
• ambient temp when readings are taken

dicktheslice

The results from hvac are as follows
00819 -High pressure sensor G65
010 Open or short to plus

group 1 current. = 0.000amp
Load 0.0%
Load 0.0%
Absolute pressure 1.0 bar

group 2 = 13.0 12.0. 0.0. 0.0

this is with aircon on

group 2 =. 6.0. 12,0. 0.0. 0.0

this is with econ on

maxandtara

High & Low pressure reading will verify refrigerant in the system.

The data you have only shows what your already know. A/C not working.

Did you do a vacuum check before you gassed your system ?

dicktheslice

The system was regassed at a aircon company
so I assume it was
the only thing I was told was that it didn’t work as got a g65 fault code
I replaced the sensor and the pressure went from 1.0 bar to 9.8 bar
it has now gone back to 1.0 bar
I will look on Saturday and check all connections and rescan and post the results
thanks for your reply

maxandtara

Go to this posting on Rosstech

If your system was gassed, VCDS should indicate that your hvac is pressurized (more than 1.0 bar of pressure).

Starting at 9.8 bar down to 1.0 bar in a short period of time indicates a leak in your system.

You need to find you leak before you do anything else.

"G65 Pressure vs. Temperature chart
(When key is on, engine is off, static system pressure)

15C - 59F - 4.0 bar
20C - 68F - 5.0 bar
25C - 77F - 6.0 bar
30C - 86F - 7.0 bar
35C - 95F - 8.0 bar
40C - 104F - 9.0 bar

Important to note about the G65 sensor:
- A reading of 0.0 bar would indicate an absolute vacuum
- At Sea Level (atmospheric pressure) the typical reading is 1.0 bar

https://forums.ross-tech.com/showthr...he-HVAC-Season

dvs_dave

You realize that means the AC compressor is turned off, right? Econ (short for Economy) needs to be “off”, not “on” for the AC to work.

dicktheslice

Fitted new g65 sensor
part No Hella 6ZL 351 028 401

these are the test and results obtained

ignition on but engine off approx 20degrees
M/b 001
0.000 0.0%. 21.5%. 5.6 Bar
current. Load. Load. Ab press

M/b 002
5.0. 12.0. 0.0. 0.0

Engine running

M/b 001
0.000 A. 0.0 %. 28.5 %. 8.4 Bar

Mb002

13.0. 12.0. 0.0. 0.0



Output test A/C Compressor Regulator Valve (N280)

compressor off.

0.000 A. 3.5% 28.5%. 8.4 Bar


compressor on

0.750 A 79%. 28.5 %. 8.4Bar


with this test I can hear the compressor run and engine revs drop
the large aircon pipe gets cold

hope this helps

dicktheslice

I tested the voltage from the G65 sensor (unpluged from the sensor) brown wire 12 volts(live feed )

Middle connector had 13 volts (output) Is this correct as i assumed there should only be a pulsed charge on this wire when connected to the sensor

Is this the reason why its not starting the compressor up

maxandtara

dicktheslice,

Please clarify.
Based on what you said:
repair 1

• replaced g65 sensor
• gassed the system
• (from your readings) r134 leaked

are you on repair 2 ?

• 2nd g65 sensor
• gassed the system again ?

now you are doing all this testing on components correct ?