Getting ear ache off SWMBO about the air con no longer working on her trusty vRS... button works, but no cold air.

 

So ran a VCDS scan and got the following codes:

 

00819 - High Pressure Sensor (G65) - Signal too low

 

00898 - Control Circuit A/C compressor - Open or Short to Plus.

 

I'd assume a wiring fault ... can anyone point me in right direction please?

 

I suspect checking the wiring from the compressor and following back will highlight an issue somewhere... but what is the G65?

 

Any help appreciated.

 

Sorry I might be operating under the delusions of knowledge imparted by drinking wine - but, the compressor control signal wiring might just be one of the two sets of connectors under the battery area, the other being the alternator control one.  The only pressure sensor/switch I know about is plumbed into the AC pipework and should be easily found by following the bigger pipe.

I'd guess that he 898 fault is a bust wire, as you suggest.

 

The G65 fault may go away when the other is fixed, not sure.

It's the sensor that tells the HVAC module what the refrigerant pressure is doing, often a low reading means re-gas time, but in your case, get rid of the other fault first and see if this one follows or stays.

 

Here's where I think the sensor is:

 

All good so far, I was going to add "check the fans are working correctly" to complete your round up of things needing done!

 

Edit:- I see that I seem to have been wrong as to where the pressure sensor/switch is though, so it is on the small supply/liquid line!

Edited 7 June, 201610 yr by rum4mo

Ok, so likely a wiring fault as I suspected related to the 00898 fault ... searching on here shows the connector for the alternator sensing light? That's on the gearbox if I remember correctly? Same one?

 

I'll leave the G65 error until wiring checked.

 

Thanks for the quick responses!

All good so far, I was going to add "check the fans are working correctly" to complete your round up of things needing done!

 

Edit:- I see that I seem to have been wrong as to where the pressure sensor/switch is though, so it is on the small supply/liquid line!

 

Internal fans or external on the radiator?

Ok, so likely a wiring fault as I suspected related to the 00898 fault ... searching on here shows the connector for the alternator sensing light? That's on the gearbox if I remember correctly? Same one?

 

I'll leave the G65 error until wiring checked.

 

Thanks for the quick responses!

Different connector, but hanging off the same bracket on the gearbox. Wiring at/near compressor is also fairly vulnerable to damage.

Different connector, but hanging off the same bracket on the gearbox. Wiring at/near compressor is also fairly vulnerable to damage.

 

Both got from underneath the car I assume?

Yep, easy to see once any engine undercover is out the way.

 

Just checked and confirmed G65 location as above pic, by unplugging that connector while VCDS was on measuring block 2, Auto HVAC module. G65 pressure went to zero.

Yep, easy to see once any engine undercover is out the way.

 

Just checked and confirmed G65 location as above pic, by unplugging that connector while VCDS was on measuring block 2, Auto HVAC module. G65 pressure went to zero.

 

Perfect! Thanks... will test G65 once I locate this wiring fault. Job for tomorrow evening...

00898 - Control Circuit A/C compressor - Open or Short to Plus.

 

 

I had the same problem, you need to get under the car and inspect the wiring to the N280 control valve on the compressor, when you locate the compressor, you'll see a black wire, follow this and make sure all the connections etc. are in properly. There was a broken connector on mine. See thread with image on page 2:

 

http://www.briskoda.net/forums/topic/397269-air-con-troubles/

 

If the wiring is OK, you can test to see if the N280 or the compressor itself is at fault, testing procedure is decribed in the first post here:

 

http://forums.ross-tech.com/showthread.php?633-Tis%92-the-HVAC-Season

 

In addition to wiring issues, or the sensor itself the high pressure sensor fault can also be triggered by low refrigerant pressure so it might need regassing.

 

HTH

Edited 7 June, 201610 yr by Dazza95

Internal fans or external on the radiator?

 

Sorry for the delay in replying, I was meaning the fan(s) on the radiators, lots on this forum about what to do there.

Sorry for the delay in replying, I was meaning the fan(s) on the radiators, lots on this forum about what to do there.

 

Just checked... the fans do not rotate when air con is on...

I had the same problem, you need to get under the car and inspect the wiring to the N280 control valve on the compressor, when you locate the compressor, you'll see a black wire, follow this and make sure all the connections etc. are in properly. There was a broken connector on mine. See thread with image on page 2:

 

http://www.briskoda.net/forums/topic/397269-air-con-troubles/

 

If the wiring is OK, you can test to see if the N280 or the compressor itself is at fault, testing procedure is decribed in the first post here:

 

http://forums.ross-tech.com/showthread.php?633-Tis%92-the-HVAC-Season

 

In addition to wiring issues, or the sensor itself the high pressure sensor fault can also be triggered by low refrigerant pressure so it might need regassing.

 

HTH

 

Great information thank you. I'm very experienced with working on cars, but I freely admit I know little / nothing about aircon systems!!!

Just checked... the fans do not rotate when air con is on...

That might just be because of the compressor wiring issue.  Try (with ignition on) shorting brown to brown/blue  (low speed, both fans) in the radiator thermoswitch connector, then brown to brown/green (high speed, both fans; or just main fan if AC fan is single speed).

That might just be because of the compressor wiring issue.  Try (with ignition on) shorting brown to brown/blue  (low speed, both fans) in the radiator thermoswitch connector, then brown to brown/green (high speed, both fans; or just main fan if AC fan is single speed).

 

Agreed... tonight I'm raising the car and getting underneath to trace the wiring from the compressor, back to the gearbox end at the connectors. IIRC last time I was in that area I thought they looked pretty ropey! 

 

Car has done 150k miles

 

It's a dual fan setup... 2006 vRS.

Edited 8 June, 201610 yr by Mr OCD

Found wiring faults by gearbox ... Loom in such a mess on those two plugs I stripped it out right back to battery and chopped connectors out!

Scan - Delete codes and re-scan shows just the G65 error which I assume is due to low gas?

Found wiring faults by gearbox ... Loom in such a mess on those two plugs I stripped it out right back to battery and chopped connectors out!

Scan - Delete codes and re-scan shows just the G65 error which I assume is due to low gas?

Glad it wasn't something more serious.

It could be, what is the reading from the G65 sensor in measuring block 02?

Edited 10 June, 201610 yr by Dazza95

Not checked ... What should it be?

Bugging me so I'm going to plug vcds in again in moment and check measuring blocks...

Bugging me so I'm going to plug vcds in again in moment and check measuring blocks...

There's a little table in this thread showing what the pressure should be in line with outside temperatures. Can't see to copy it on my phone

http://www.briskoda.net/forums/topic/401703-intermittent-aircon-fan/#entry4641513

Excellent info!

So I'm looking for any pressure between 0 and 9 bar ... Fan won't start till 9 bar and above in system. Let's have a look ...

0% compressor load

0.0 bar at G65

Hmmmmm

Check at G65's 3-way connector for ignition 12V between pins 3 and 1 (3=+12, 1=earth). If OK, check continuity of pin 2 (red/white wire) to pin 1 of the 16-way connector at the AC control module. Not sure how easy the latter is/isn't to get at.

If it was the wiring for the G65 then it would be short to ground, not low pressure / signal?

Ross-Tech says most likely low refrigerant pressure in system.

Edited 11 June, 201610 yr by Mr OCD