Air Con Sensor DIY

[J305]

Hi, a garage diagnosed the problem and told me that the pressure sensor needs replacing for the Air conditioning, but they want to charge me £270 for it, I'm not sure if this is the correct part number, but I've found it for a lot cheaper online.

A4 B8 1.8 TFSI S Line 2008

7H0820896 = O Ring
4H0959126 = Pressure Sensor

Total: £23.02

I'm not sure if those are the correct parts, here is a picture of my sensor.

 

[EXSpartan36]

Just had a look on ETKA the O-ring P/N is correct, The P/N for the pressure sensor is now 4H0959126A.

 

[rum4mo]

I'd think that unfortunately, due to the on going issues that VW Group have had with this sensor, the only good plan will be to buy the new sensor at your local Audi dealer, or online from audipartsdirect or someone else who used to reside on this forum.

 

[J305]

Just had a look on ETKA the O-ring P/N is correct, The P/N for the pressure sensor is now 4H0959126A.

Thanks! Could I change it myself? By somehow draining the gas that's already in there? Then get it regassed professionally

 

[EXSpartan36]

It doesn't need to be de-gassed it sits on a one way valve. It's tightened to 5nm so should come off fairly easily

 

[Owyn]

I just did mine tonight, I got the sensor and o ring from an Audi garage, it was something like £63. You literally unplug it, screw it off, screw the new one on and plug it in. Fixed!
There is a valve underneath it so there isn't any real gas loss.
The new one is a little different, the old one (like you've got) uses a 17mm spanner, the new one a 24mm spanner.

 

[J305]

I just did mine tonight, I got the sensor and o ring from an Audi garage, it was something like £63. You literally unplug it, screw it off, screw the new one on and plug it in. Fixed!
There is a valve underneath it so there isn't any real gas loss.
The new one is a little different, the old one (like you've got) uses a 17mm spanner, the new one a 24mm spanner.

Thanks for the response! It sounds simple enough, I tried to unplug the top connection but it made a slight hissing sound like air was coming out, is that a problem?

 

[Owyn]

The way it works is the sensor presses the stem of what is essentially a tyre valve, this lets gas into the sensor where it stays at the same pressure as the system. The o ring stops the gas escaping from inside the sensor into the atmosphere.
As you take the old sensor off the small bit of gas that is sat in the small void in the sensor will come out, little hiss. The valve will close and nothing more will come out.

The wire has no direct connection to the gas, if you heard a hiss when unplugging the wire then I guess the o-ring is knackered and any movement means the gas leaks out. If the o-ring is shot you may be a bit low on gas when you fix it.

Its a dead easy job but make sure you got the bits before you start it as if you take the old sensor off and leave it off you may get a load of dirt in the valve.

 

[rum4mo]

Remember to remove the old switch quickly to avoid leaving it in the position where it is still just opening the self sealing valve below it while being able to vent that leaking gas off to atmosphere. It will be the same when you fit the new valve, there will be a quick loss of gas which will stop once you have quickly completed fitting the new switch.