Change the G65 Aircon Thrust/Pressure Sensor

I've had some good advice from members of this forum and so, after gaining some valuable knowledge, I thought I should try and put something back in.....

My car, an A4 2.0 TDI S-Line Avant, had a non-functioning aircon system when I bought it 3 weeks ago. The ECON light wouldn't go out and there was no cold air. I had the system re-gassed but this made no difference as one of the a/c fuses kept blowing. The garage told me it was the compressor but when I investigated later it was fuse 6 that was blowing; a 5-amp jobbie that protects the aircon pressure sensor, nothing to do with the compressor. So after some top advice from here I bought a new thrust/pressure sensor from my dealer (£57.14) and set about fitting it myself. This is what you have to do:

1. Remove the complete front bumper (no point in explaining how as there are ample articles on here and on the web with supporting pictures). I did this on my own and it took 30mins. Make sure you have a blanket underneath the car to lay it on. No need to disconnect the wires to the foglights.
2. Remove the N/S headlight assembly by loosening, but not removing, the two clamp bolts at either end of the unit (the outside one is located down a hole in the plastic moulding). Remove the screw/bolt from the top of the unit, take the wire cluster from the back and it will pull out.

Once out this is how it will look:

Attachment 17358



The thrust sensor is located just left of centre in the image above. On the car it sits on a spigot that leads from one of the a/c pipes that follows the N/S of the radiator. As I tried to disconnect the plug the whole outer shell of the unit broke away and what was left was full of corrosion. I took this as an encouraging sign; after the rigmarole of removing the bumper I would have been disappointed to have found everything in working order!

Here is a close up of the corroded sensor:

Attachment 17110

I put on a pair of motorbike gloves and some sunglasses and set about removing the remains of the sensor. You'll need an open-ended 17mm spanner to do this. Mine came off very easily but I'm told they can be tight all the way off the thread. Anyway, the system has a schrader type valve on the spigot and so minimal gas is vented - it certainly doesn't need to be re-gassed afterwards (assuming you have a charged system).

Once off, clean the thread and make sure the O-ring is okay before screwing the new sensor on. It doesn't need to be horribly tight; just up and then a good nip. While the bumper is off I took the opportunity to lube the threads of the headlight clamps and squirt WD40 over the corroding metal parts.

I was fortunate; when I started the car I was able to push AUTO and the ECON light went out. This was accompanied by a slight drop in RPM and cold-ish air filling the cabin - hurrah!

So, if you have no aircon and the ECON light doesn't go out when you press AUTO then this should be one of the routes you check before replacing the horribly expensive compressor and its attendant components.

Hope this is of help to someone.....

Hi, great post. I am experiencing the same problem with my b7 s line. Can you advise what the part number is for the replacement sensor, would you get this direct from VW or can you pick these up from Audi?
Cheers

I'm away on business so sorry, don't have the part number to hand. I think the sensor is common to VW and Audi so just tell them you need the G65. My dealer said it was a stock item as they fail all too frequently.

Someone else on here managed to change the sensor without removing the bumper first but I'd take the front off to make it easier to get to everything.

Hey guys, just changed this sonsor but econ light still wont go out, do i need to get the codes cleared or something or could it be a fuse? is so any info would be appreciated, cheers

Quote:

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Originally Posted by stoksie

Hey guys, just changed this sonsor but econ light still wont go out, do i need to get the codes cleared or something or could it be a fuse? is so any info would be appreciated, cheers

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Try a regass.

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thanks for the reply mate, na its not the gas, the first thing i did was have it regassed, then changed the sensor and like i said nothing, ive since read about fuses so went and checked and surprise surprise the fuse was blown, so replaced it, and the econ light goes out but theres no change to the air being delivered at all (no cooling) so im fearing the worst i.e compressor now, anyone have any ideas before i go to audi and pay through the nose?

Does the clutch on the front of the compressor work?

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No idea mate i cant see when looking down the front of the engine bay, is there any way to check, there doesnt appear to be any sound, any ideas how i can check for sure?

I would expect a small change in engine revs when the clutch cuts in.
Some of the more experienced techs on here might be able to help.

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Look deep down it'll be driven off the crankshaft pulley,see if the clutch spins when operating the econ switch,the clutch not just the pulley.Next check if its being commanded to operate by seeing if there's voltage on the connector.

I've seen this job in other posts mention it's possible to do without taking the bumper off and just getting access with the N/S headlight removed. Is this the case or is it best to remove the bumper? I'm changing mine on an A6 1.9tdi (2002).

Thanks. PD

Hello PD,

I can't answer your question sadly as we have two completely different models. If the A6 is anything like the A4 then I'd suggest taking off the bumper as I did; it's a pain but not difficult and allows easy access to the sensor (assuming it's in the same place on the A6).

Good luck!

Thanks guys, I just did this on my A6 C5 avant, took less than 5 mins, no need to remove the bumper or headlight. I did remove the grill for the fog light though and was able to reach my hand up.

The result, lovely cold air again!!!

Thanks muchly

By no means am I a mechanic, just a guy who knows how to troubleshoot with the help of Internet resources.

I'm trying to diagnose the dreaded ECON light issue with my 2008 Audi a4 b7 2.0 TFSI Quattro Wagon*. So far I've checked the low and high pressure with the engine off. Low PSI sits around 22 PSI and High 21 PSI in 70F weather. To my understanding, it's a good thing both pressures are close in range and leads me to believe I'm not dealing with a leak? With the engine on, the Low and High pressure do not change which makes sense since the a/c compressor appears to not engage?

Attachment 28102

Removing the under body cover, I was able to see the a/c compressor's front face plate spinning. I gathered information to believe this tells me the compressor is not seized and should be functional?

I've also checked the fuse box for faulty fuses that would correlate with the a/c. I'll reconfirm tomorrow with detailed information as to which fuses I checked to be good.

Furthermore, I drove the vehicle around for about 10 mins with the temp "low" and fans maxed, popped the hood and felt both the high and low pressure lines which were neither hot or cold. Not sure what this tells me yet other than the compressor not engaging..

I feel like I've confirmed enough that the issue may reside with a faulty sensor, and in this case, the G65 High Pressure Sensor.

Advice from anybody would be greatly appreciated.

Thanks and I'll keep this forum posted on what the end results are.

Positions 1 and 6 fuses appear to be intact. I also learned that if the "Econ" light does not go out when "Auto" is on, it indicates that there is a problem with one of the system components, which in my case is true.

It may not work for the specific case above, but since this seems to be a popular G65 change thread I thought I'd add a link to what worked on our Touran: Replacing G65 air conditioning pressure sensor on 2.0 TDI Touran (AZV engine)

Just had my system regassed yesterday and my econ light is staying on with the compressor not coming on. ATS said there are no leaks in the system. Could the regas have caused the pressure switch to go faulty, can't say for 100% if the econ light staying on or not before the regas.

No one nearby to do a scan, worth just swapping the sensor?

If you have a digital display temp controller you may be able to get the error codes by turning on power (engine start not needed), then holding down AC (or ECON) and then RECIRC for about 5 seconds. Display should show "iO" (for "in order" / OK) or an error code (IIRC). One of the up / down controls or buttons (eg left dial on our Climatronic unit) should then let you move through the set of error codes until you see iO again. These are in hexadecimal, and 333 means 3*256+3*16+3*1 = 768+48+3 = 819 which you can lookup on Ross Tech to be 00819 - High Pressure Sensor (G65): Open or Short to Ground, which is the usual error that you get when it is bust.

For my 2007 A4, I had 00819 - High Pressure Sensor (G65): Open or Short to Ground
Bought a new sensor and O-Ring for £62 @ West London Audi. Next day collection from their parts store. Super friendly guy called Nixon.
P/N for the sensor: 3R0 959126
P/N for the O-Ring: 7H0 820 896

I replaced in 1 hr. No need to take the entire bumper cover off.

This sensor lasted 11yrs on my car and after that period of time in a hot engine bay, things have probably become crusty and brittle and those things break easily. So I removed the Headlight fitting shown in the middle of the pictures - this enabled full force to be applied when removing the old sensor. It was jammed on and I found if I tried to apply to much force at and angle, the pipe that this sensor is fitted on starts to bend. Be careful.

Attachment 35124
Turn the wheel and unclip the bumper cover. head has been rotated out of the way. I didnt need to unclip the electrical connections either


Attachment 35125
Headlight bracket removed

Attachment 35126
You can see the very limited space to work in - Valve is removed at this point

Attachment 35127
Valve removed - exposing the shiny threaded end of the pipe. I sprayed WD40 on the threads before rolling the new O-ring on. IMHO, the threads are coarse and could nip the new O-Ring

Attachment 35128
Removed G65 sensor: this side was facing into the airflow behind the bumper cover. After 11 yrs, the air and rain etc must have distorted the casing and allowed moisture to enter which must have compromised the electrical contacts inside.

Thanks to OP for starting this thread some time ago now.
It helped me - I hope my pics and additional info help someone else

Ordered a cheapo Vagcom cable from ebay which arrived today only to find it doesn,t cover the B7 model. Selected B6 on the offchance and it seems to have worked, says G65 open or similar. Will order a new one and o-ring tomorrow, thanks for the photos and the warning not to damage the pipe which I have no doubt will help me :beerchug:

Took bumper off fully and replaced the sensor, started car and econ light was out when I switched on heater. Now ice cold again, happy days.
Hardest part was taking the wiring plug off the sensor, saying that I'm just away to put the bumper back on again ��

Most painfull part was paying for the sensor £68.75 from Highland Audi in Inverness