" wrote in
:

On Jun 4, 7:26*am, Tegger wrote:

The icing sensor is about the size and shape of a
soda- bottle cap, is potted, and has two thick electrical wires.
Maybe it's stuck and is not switching, like gregz's example.


It sure sounds like a stuck contact problem, either in the deicer
sensor or in the 3-position switch,



Just for fun, I just pulled the icing sensor and took it apart, which
required care, and judicious use of a Dremel.

The soda-bottle cap's (see above) closed-end sits against a turn of the
cooling coil, held there by a clip. Just inside the cap, where a washer
would be in a real bottle cap, is a disc-shaped bimetallic spring. This
spring says "LI-LI-LI; TOD-TOD-TOD" repeatedly on one side, and is blank on
the other. The blank side faces the closed-end of the bottle cap. Against
the printed side sits a tiny piston that bears against a set of contacts.

At room temperature, the spring is slightly domed towards the blank side,
and the piston does not touch the contacts. Below freezing, the dome
suddenly pops so that it is domed towards the printed side. This action
pushes the tiny piston so as to open the contacts. This breaks the current,
and the compressor would stop running.

This means the contacts are normally closed. A VOM shows me that the
contacts are in fact closed (zero ohms) above freezing and open (infinite)
below that, which is what I found before I dissected it.

I think I'm going to have to wait for some really hot, humid weather before
I can gather more information.


--
Tegger