Sorry, I can only offer the basics below.

"MajBach" <majbachDELETEME@sympatico.ca> wrote
snip
> Now, I did have a Honda mechanic look at it briefly while carrying out a
> different repair and he stated it is the expansion valve.
> This was a couple of weeks ago and I wasn't in any hurry to have it fixed
as
> the A/C seemed to work fine - it just made that noise. The only other
> unusual observation was that it very often blew water vapor through the
> vents, which I not only thought was normal, it's also a little cool (no
pun
> intended). I now feel this visible exhaust seems so excessive, it is not
> normal as it does it even on dryer days.
> Today, I hopped in the car; it was sunny and hot. The A/C was very
> ineffective while driving in the city. After I got on the highway, the A/C
> seemed to blow cooler air and was sufficient to keep me cool but only on
> full blast. It had also turned overcast.
> The last time I checked, I did see water pooling under the car (I didn't
> check it today though) . I have had a clogged drain tube in the past which
I
> did notice just by hearing the water sloshing around and I managed to
unclog
> it myself. So I don't think that has anything to do with my problem now.
> So what I want to know is, (as I believe my mechanic's diagnosis) :
> WHAT IS AN EXPANSION VALVE?

The expansion valve is one of four major components in the refrigeration
cycle. Each component accomplishes a specific function. These are:

Evaporator: Transfers heat from your passenger space to the refrigerant
inside the system's pipes, causing it to boil to a gas. Refrigerant pressure
is "low" and constant, causing the temperature of evaporation to be low,
facilitating heat transfer from high temperature sources (your passenger
space) to the lower temperature refrigerant.

Compressor: Increases the pressure of the refrigerant gas in preparation for
condensation and to keep the fluid moving around the cycle.

Condenser: Transfers heat from the refrigerant gas to the atmosphere,
causing the refrigerant to become a liquid. Refrigerant pressure is "high"
and constant, causing the temperature of condensation to be high,
facilitating heat transfer from the high temperature refrigerant to the
lower temperature atmosphere.

Expansion Valve: Reduces the pressure of the refrigerant gas in preparation
for the evaporator

>What does it do and can I fix it myself? I have
> fixed clutches and brakes on my cars before so its not like I'm useless
with
> tools or anything. But, is this valve in line with the pressure, i.e. does
> the coolant has to be captured first with special equipment?

Yes, it's in line with the "pressure." The refrigerant is going to "pour
out" while removing the expansion valve.

Dunno the other answers to your questions. I'd try a more intense Internet
search and/or a Haynes or Chilton manual.

> I have done some major searching already in this and other N.G.s and
haven't
> really seen a concrete answer to this question, only on how to diagnose if
> it is an expansion valve that is faulty. However, I have seen some 'fixes'
> that involve cleaning and removal or bending of sensors etc. and wondered
if
> there was a inexpensive fix for this. Finally, is it likely that I have
lost
> coolant through this faulty valve? Like I stated, this noise occurred all
> last summer and to date this summer but A/c seemed to function. Today it
was
> noticeably inefficient. I did see a post that stated just because I have a
> bad valve and no cool air doesn't mean I have lost coolant. Just need to
> know what I am in for dollar wise.