Repair HunterFan digital thermostat?

This is Hunter Fans Digital Thermostat Model 44360.
It has worked to control my gas furnace for 6 years.
I like it's design and features. Hunters have a bad rep with
service people from what I've read in HAVC forums. But
I like mine and would like to repair it.

Lately its calibration is off by 2 to 4 degrees. I know this
by comparing it with three other thermostats: a new Honeywell
replacement digital and 2 old Honeywell mercury-switched thermos. In
addition, a room thermometer confirms the others' readouts.

As the room reaches warmer temps the Hunter's readout will
become more unstable and gravitate towards the 4-degree
range.

All this may or may not have started after I knocked the Hunter off
the wall. There was no apparent damages.

Looking at the cb there is a protected part that sticks out.
It has a plastic guard around it. The circuit board has the marking
"RT" . It appears to be a very small glass bead or
mini-mini LED type of device. Exhaling warm breath or placing my
fingers around the guard will cause the readout to rise.

So I'm guessing this is some type of themistor. There appear to be no
other marking on it. But it is so very small.
It kind of looks like this:

http://media.digikey.com/photos/Honeywell%20Photos/112-104KAJ-B01.JPG

and more info on these therms at:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=480-3117-ND

Would replacing this fix my thermostat or is there a bigger problem
with the calibration? If the former how can I id the
replacement?

Thank you in advance.
less

 

[David Nebenzahl]

On 2/27/2009 10:58 AM lesswar@gmail.com spake thus:

This is Hunter Fans Digital Thermostat Model 44360.

Lately its calibration is off by 2 to 4 degrees.

You've probably already looked for this, but are there any adjustments
(like trimmer pots) on the board?


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"If this stuff worked, you wouldn't need me".

- lifted from sci.electronics.repair

 

[krw]

In article <49a83a82$0$2698$822641b3@news.adtechcomputers.com>,
nobody@but.us.chickens says...>

On 2/27/2009 10:58 AM lesswar@gmail.com spake thus:

This is Hunter Fans Digital Thermostat Model 44360.

Lately its calibration is off by 2 to 4 degrees.

You've probably already looked for this, but are there any adjustments
(like trimmer pots) on the board?

There is often a "heat anticipator" setting that when whacked will
throw the calibration off. It's purpose is to compensate for the
thermal mass of the building and look at the rate of the
temperature rise so it doesn't overshoot. Some are better than
others.