C Class Air Con hiss

[Pipemaster]

In our 2001 C Class the air con hisses ( or it could be described as rattles) in the pipes behind the dashboard. it works but the noise is annoying. When you tune the A/C off the noise eventually goes as I assume the gas stops being pumped around the pipes. Could this be a sign that the systems requires recharging or is it a symptom of something else?

 

[type49]

If it is a hiss (as a rattle is a completely different noise), then this is the noise the expansion valve makes when the pressure is low in the system. You probably need a re-gas + leak-tracer dye added. The most common place for a leak is at the bottom of the condensor, at the pressure sensor area.

 

[Pipemaster]

Right then

it's of to the a/c place. I would say its more of a hiss but not one that seems to be venting as it does go away and come back again (I guess as the cabin attains temp and then gets hot) The machine they use automatically flags up when a leak is detected so that will show me if the systems integrity has been breached. I'll let you know.

Thanks Type49 hope the dog is well