randolphscott

Does anyone know about expansion valves and when they need to be replaced?
The AC went out on a newly purchased e320. Couldn't get the local MB service dept (Walnut Creek) to return calls, so I used a local mechanic. Two different mechanics said the expansion valve needed to be changed. The guy I bought the car from insists only the o-rings on the receiver drier, or possibly the whole reciever-drier, needed fixing.
Is there a definite test, or is it up to the parts seller?
Does anyone really care?
(BTW, it blows cold as I like now!)

Thanks,
R

MBTech21

The expansion valve is a metering device that changes high pressure liquid refrigerant into low pressure liquid refrigerant before it goes into the evaporator (where it absorbs heat and changes to low pressure gas and heads back to the compressor with the heat energy).
Things that could go wrong. stuck open (measured by pressures), stuck closed or plugged up (again measured with pressures), leaking (found with a leak detector). Usually they are replaced if a compressor fails (due to the small orfice-easy place for something to get stuck if the compressor comes apart).

Seeing as it is working now, sounds like a leak- it's usually only the o-rings leaking, however, if I was pulling the cowl apart and taking it off anyway, I would sure replace it, as cheap insurance. Hope this helps