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[Dr A. 33 1.5IE]

Dear all,

This is a question for airconditioned Alfa 33 onwers (that includes you Gritsop!!!)

What is the role of the expansion valve of the aircon unit and why has to stay clean of dirt to function properly??? Do I have to cover it with something???

Thanks
_________________
1994 Alfa 33 1.5 IE Cat. 220.000Kms and still going strong!!! (Από την Αθήνα και τώρα στην Λευκωσία)

[gritsop]

Hi,

Well... the role of the thermal expansion valve (TVX) is to

1) meter, 2) modulate and 3) control the flow of refrigerant towards the evaporator

This valve is the physical dividing point of the high and low pressure sections of the A/C system:

Low pressure section: expansion valve -> compressor inlet
High pressure section: compressor outlet - > expansion valve

1)Metering: an orifice located inside the TVX changes the pressure of liquid freon from high pressure to low pressure

2) Modulating: A thermostatically controlled valve inside the TVX opens or closes path towards the orifice thus ensuring that the evaporator receives the proper amount of freon. Low pressure freon created at the TVX makes it possible to vaporise through the evaporator and absorb heat from the vehicle interior.

3) Control: TVX quicly responds to heat load changes. As more heat is sensed, the path moves to an open position in order to increase freon flow; if decreased heat is sensed then the path closes in order to restrict freon flow towards the evaporator (e.g high engine speed)

Generally speaking the TVX has its primary role to permit the proper amount of liquid freon entering the evaporator by sensing its heat, and lowering its pressure.

Since the TVX is a temp sensing device - among other tasks - it is suspectible to external heat sources which may "fool" its modulating role.
So , there are materials like cork tape which wrap around the valve in order to isolate heat coming from the engine.

In our case, since the position of the TVX is far away from heat generating sources like the engine or the exhaust, there is no need to insulate it. In other cars that the TVX is right behind the exhaust manifold (usually in transverse engines setup) then for sure TVX is insulated with cork tape.

You may also read the article in Bobbber's site http://www.alfa-restoration.co.uk where this issue is discussed in more detail.

Hope I 've cleared things out

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop