W203 expansion valve

[jg0709]

Hi,
i had an air con specialist out to check and regas air con system and was told that the expansion valve was faulty and needed replaced. The car is a C200K W reg
(W203), how difficult is it to replace and is it accessible via the bonnet? I have checked the internet for information and haven't found much on it at all.

Any help would be appreciated.

Many thanks.

 

[cleverdicky]

Haven't seen your particular model, but know exactly what it is and how it works.
(Its complicated but a simple function)
They are sometimes called a TEV or thermostatic expansion valve.
Basically like a variable venturi carb. You need more, it opens up to let you have more.
But it does so by measuring the temperature of the expanding refrigerant evaporating temperature inside the evaporator depending on heat load. And then a 'adds' a bit.

This crucial bit is called the 'superheat setting' and measures how much above the evaporating temperature the evaporator is, and then meters the amount of refrigerant it lets through to maintain the correct evaporating pressure.

They rarely go wrong, but they can. Its a bit like a thermostat after all.
More likely to be blocked. Knowing where it needs to be i doubt for a second its easy to get to, and i also doubt its a replaceable part on its own. More likely comes already part of the evaporator.
Imagine where your heater matrix is, then a bit deeper.

Did they say (exactly what was wrong and why) I would get a 2nd opinion, and consider a good system flush.

There are two scenarios to confirm.
Very high pressure on the liquid line and very low pressure on the suction line (blockage / stuck closed)

Or equal (or very nearly) pressures both sides of system. (stuck open)

I personally would change the car before wanting to rip it apart just to change the tev.

Good luck.

 

[jg0709]

Thanks for your detailed reply, i thought it would be a swine to get to.
Will try a system flush and failing that will leave well alone and just open the window during our brief summer.

Thanks again.

 

[cleverdicky]

No problem. But one thing I should (have) make clear.
When I say 'flush' i mean done properly with the right chemicals, solvents.

Whatever NEVER use water. Would be a disaster.