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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 10083
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Have a T8411R Honeywell that no longer displays. Is there a

Customer Question

Have a T8411R Honeywell that no longer displays.
JA: I'll do all I can to help. Tell me a bit more about what's going on so we can help you best.
Customer: Is there a battery source?
JA: Is there anything else the HVAC Technician should be aware of?
Customer: Unit is over 10 yrs old
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the HVAC Technician about your situation and then connect you two.
Submitted: 2 years ago.
Category: HVAC
Expert:  Phil replied 2 years ago.


This should be the manual for that thermostat.

If you have a volt meter test for 24 volts as marked in the screen shot below

If you have 24 volts there, the thermostat is bad. If you do not have 24 volts across those two terminals

then there is something wrong inside the heat pump air handler, a blown 24v fuse, bad transformer, broken wire or etc.

Let me know if you need training on how to do further diagnosis and repair.

We can go from there.