Aircon pressure sensor melted..

AndreasR

Member
Norway
Hello,

Removed bumper to change pressure sensor, this is what was waiting for me..
3A3278E1-7C3D-4CB4-B910-468AC327BE7D.jpeg
126CB9B1-59B4-415E-B60E-D50E8145CDB5.jpeg61E5FFFC-387F-49F7-89E8-868D7AFB53E2.jpeg

I’ve not had the car for long, so not sure how long it’s been like this. Anyone seen this before? Why does it happen?
 
The good news is that you can change the sensor with losing any refrigerant! Or at least, you should be able to. Assuming that you still have some!

RAB
 
The good news is that you can change the sensor with losing any refrigerant! Or at least, you should be able to. Assuming that you still have some!

RAB

Well, that’s a different story, the pipe and sensor are like fused together, not possible to loosen it 😅
 
What could've happened? How much did you drive the car like that? What kind of fault codes did you get? And how? I mean HOW?
 
No idea, that’s why I’m asking you guys 😅

Car was bought as cheap project car, might have been like this for a long time for all I know.

Standard fault code for a non-working sensor:

C7B15E72-601D-43B5-AAAF-65436A80A6B7.jpeg
 
Mine wasn't as spectacular, but the corroded / shorted sensor prevented the power steering from being functional by repeatedly causing fuse 38 to blow. As soon as it was unplugged it was possible to replace the fuse and steering came back. New sensor fitted along with a new a/c heat exchanger by WOM in the refurb last autumn.
 
true, but if the short was taking place inside the sensor body and earthing internally to the a/c heat exchanger it's not surprising the connector has melted - the real surprise is that Fuse 38 didn't blow first (has it been replaced by a fuse with a much larger value - mine had a 25A (blown) fuse in it instead of the expected 10A. The sensor on mine broke in half while I was trying to undo the connector, revealing that it was full of oxide and crud hence the electrical fault. Connector itself was undamaged in my case.

How does it happen? I imagine the relatively exposed location of the sensor, especially if it is in an area that suffers a lot of water / ice and road salt presumably is what allows the sensor to eventually become compromised structurally and then once moisture is getting in the short will happen pretty quickly. 10A at 12V is 120W of heat to dissipate.
 
There should be nothing like 10A through the sensor - more like 10mA! Audi always seem to use cheap sensors; given the modest temperatures and pressures they are subject to, they should easily last the lifetime of the car. It might be a good idea to cover the replacement with heatshrink; Audi should have used a sensor and connector with an appropriate IP rating.

RAB
 
Last edited by a moderator:
That's not the sensor! It's the connector to the sensor. Tightening torque for the sensor is only 5 Nm, so should be easy to remove.

RAB
I know that 😉 Just a reference to the short/ground 👍
5nm might be the factory spec, but it’s stuck anyway. Pipe starts to twist when applying pressure, so probably corroded.
 
get piece of wiring replacement from breaker car to keep wiring colours as it looks like part ow wiring outside the plug is burned/melted too, try to secure piping with some clamps to undo what is left from sensor, there is an valve in pipe so not much should escape of refrigerant if there is any in there still, this is sensor type which has power to it all the time and it sends modulated signal back via third wire based on pressure level, if you took bumper off then access should be ok...i had to replace mine with bumper in so it was bit tight access for any tools
 
I know that 😉 Just a reference to the short/ground 👍
5nm might be the factory spec, but it’s stuck anyway. Pipe starts to twist when applying pressure, so probably corroded.
that's exactly what happened with mine. I couldn't get a grip on the round collar that was sufficiently strong to immobilise it whilst rotating the sensor hex-nut section to crack it off - the pipe started to get twisted. Ended up getting a new heat exchanger as they were inseparable.

Can confirm with the more recent G65 replacement on our AUA that it was possible to shift it once I got a decent hold on the sensor without it torquing the attachment tube.
 
Back
Top