outside temp reading jumpy

Posted by Jeff D on January 13, 2009, 12:39 pm

I have a Lennox heat pump with the outdoor temp probe. It sometimes changes
5-10 degrees within a few minute period. I've replaced the telephone style
connectors with wire nuts and had the service man replace the outdoor sensor
while the unit was still warrantied.
Today I have a new problem, the thermostat goes blank periodically for a few
minutes then returns to normal. It's not just the display going blank
because I hear an internal relay clicking when it dies and comes back to
life. I went to all the wire connections and jiggled them but couldn't get
the the thermostat to crap out. Any ideas on a solution to either or both of
these problems. I'm out of ideas beside ringing out the wiring for shorts or
breaks and replacing all the telephone style crimp connectors between the
furnace, heat pump and thermostat with screw terminals.

Posted by The King on January 13, 2009, 6:02 pm

wrote:

>I have a Lennox heat pump with the outdoor temp probe. It sometimes changes
>5-10 degrees within a few minute period. I've replaced the telephone style
>connectors with wire nuts and had the service man replace the outdoor sensor
>while the unit was still warrantied.
>Today I have a new problem, the thermostat goes blank periodically for a few
>minutes then returns to normal. It's not just the display going blank
>because I hear an internal relay clicking when it dies and comes back to
>life. I went to all the wire connections and jiggled them but couldn't get
>the the thermostat to crap out. Any ideas on a solution to either or both of
>these problems. I'm out of ideas beside ringing out the wiring for shorts or
>breaks and replacing all the telephone style crimp connectors between the
>furnace, heat pump and thermostat with screw terminals.

Rip it out and start over..

Posted by Bubba on January 13, 2009, 9:47 pm

wrote:

After all..............
its almost always the thermostat.
Bubba

Posted by Jeff D on January 15, 2009, 9:35 am

ok - well I'll make sure all the connections are clean and tight and wait
for the t-stat to fail, probably on the coldest day of the winter, maybe
today it's 11 below

> wrote:

>>I have a Lennox heat pump with the outdoor temp probe. It sometimes
>>changes
>>5-10 degrees within a few minute period. I've replaced the telephone style
>>connectors with wire nuts and had the service man replace the outdoor
>>sensor
>>while the unit was still warrantied.
>>Today I have a new problem, the thermostat goes blank periodically for a
>>few
>>minutes then returns to normal. It's not just the display going blank
>>because I hear an internal relay clicking when it dies and comes back to
>>life. I went to all the wire connections and jiggled them but couldn't get
>>the the thermostat to crap out. Any ideas on a solution to either or both
>>of
>>these problems. I'm out of ideas beside ringing out the wiring for shorts
>>or
>>breaks and replacing all the telephone style crimp connectors between the
>>furnace, heat pump and thermostat with screw terminals.

> After all..............
> its almost always the thermostat.
> Bubba

Posted by Jeff D on January 16, 2009, 11:05 am

Here's another data point regarding the outside temp sensor. It is only
erratic when the auxiliary heating is on, not sure what that interaction
could be. What type of sensor is it anyway, thermocouple, rtd, thermistor,
diode etc. Also it would be nice to get a print for the thermostat so I
know what the maze of external wiring is connected to and their functions.
The t-sat is a Lennox Signature Stat 81M28. I'm not a hvac tech, but was an
industrial electrician for 30 years and worked on the wiring side of several
hvac systems.

> ok - well I'll make sure all the connections are clean and tight and wait
> for the t-stat to fail, probably on the coldest day of the winter, maybe
> today it's 11 below

>> wrote:

>>>I have a Lennox heat pump with the outdoor temp probe. It sometimes
>>>changes
>>>5-10 degrees within a few minute period. I've replaced the telephone
>>>style
>>>connectors with wire nuts and had the service man replace the outdoor
>>>sensor
>>>while the unit was still warrantied.
>>>Today I have a new problem, the thermostat goes blank periodically for a
>>>few
>>>minutes then returns to normal. It's not just the display going blank
>>>because I hear an internal relay clicking when it dies and comes back to
>>>life. I went to all the wire connections and jiggled them but couldn't
>>>get
>>>the the thermostat to crap out. Any ideas on a solution to either or both
>>>of
>>>these problems. I'm out of ideas beside ringing out the wiring for shorts
>>>or
>>>breaks and replacing all the telephone style crimp connectors between the
>>>furnace, heat pump and thermostat with screw terminals.

>> After all..............
>> its almost always the thermostat.
>> Bubba

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