Hi All ; just a heads up - learn from my mistake.
I just had to replace my 8 year old thermostat -
- the touch-screen was failing to adjust certain settings -
including the set-temperarture - it was stuck on 64 F. degrees.
I discovered the 3 AAA batteries had corrosion - no doubt
after being neglected for 8 years ! The other little 3 volt battery
that was well-hidden - seemed fine. I replaced it in an attempt to
reset / revive the unit - to no avail.
I'm not positive that the cause was the batteries but I can't
think of anything else to blame ..
https://yourhome.honeywell.com/en/pr...ostat-rth8500d
John T.


Have you contacted the "corroded" battery manufacturer. Some guarantee
their batteries, from leaking/ corrosion. Might be worth an inquiry?


so is this progress,
the old mechanical units are trouble free for 25 years
m


I was very tempted to replace it with old-school dial-type !
... we don't use the fancy programs. But I wasn't sure if the
new electronic furnace controllers are compatible ?
As for the battery corrosion - totally my fault -
for dis-remembering that it even had batteries .. duh.
When I get the furnace serviced next month, I'll ask the
service guy if he has "thermostat batteries" on his checklist.
... it should be.
John T.