Engine Size: 1.8L
Refrigerant Type: 134a
Country of Origin: United States
The thermal expansion valve, which is internal to the box containing my evaporator, is wrapped in an elastic foam rubber. The expansion valve is directly in line to the flow of air from the heater/AC fan. Why is this valve wrapped? Should it be?
I have 2 jpg's I could attach that show this ... but, I can't figure out how, or if, I can attach pictures.
OK ... figured it out ... I have attached the 2 jpg's showing the wrapped valve.
Edited: Sat May 25, 2013 at 1:46 AM by MiataPete
You're talking about the valve itself, and not the sensing bulb, right?
Is the expansion valve positioned such that any condensate that forms on it will be caught by the "drip tray" that funnels condensate out of the car? If not, then they've wrapped it to prevent condensate from building up on it, and dripping in an area where it shouldn't be. If it is over the "drip tray" then I have no idea.
Wouldn't the " down stream " side of the expansion valve be very cold ? I would guess the foam is insulation ( as some one has said ) to cut down on condensation , at that point ?
I have not worked on an expansion valve since my youth .
Right ... the expansion valve is wrapped. The temp sensing bulb, on the other side of the evap, is open to the airflow being directed into the car.
And, yes again, if the expansion valve gathers moisture, that moisture will drop directly to the bottom of the box, and flow directly out via the drip hose.
I'm puzzled, too. Shouldn't the expansion valve be able to sense the temp of the incoming air from the fan?
Thanks for the reply.
Right, the downstream side will be very cold (hopefully ... if I don't screw up).
But, this valve is on the "warm" side of the evap ... though, obviously, both the input line and the output line from the evaporator both travel through the valve. So, the valve is touching refrigerant lines of two temperatures.
Valve gets wrapped to the fitting. Bulb gets wrapped to provide proper temp reading for the superheat.
Yes, it is a block type valve, and the temp sensor on the other side of the evap does send a signal to the PCM, to control the compressor clutch ... I figured that out, when trying to test that sensor, and having to examine the factory wiring diagram for the car.
Just this morning, at Harbor Freight (one of my favorite places in the world), I ran into a guy who works on AC systems. He said that the foam rubber wrap is common on expansion valves, and my valve should remain wrapped (my new valve .... I am buying one from Mazda).
He said that the wrap helps to maintain a constant temperature in the valve, to help avoid freezing of the internal components in the valve, during on/off cycling.
Thanks for the input ... I definitely needed help on this one.
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