I have a 20 year old honeywell dial thermostat with 4 wires, Red Green White and Yellow connected.

I purchased a Honeywell T8001F programmable and connected the RED wire to the R connection, White to W, Yellow to Y and Green to G.

There are other wire terminals like B and O .

Once connected the unit is dead, no display and acts as if there is no power. I have voltage coming in ut am wondering if it's enough to drive the unit. This particular unit does not use batteries.


A schematic would be excellent! Honeywells installtion instructions and diagnostics are horrible and I'm hoping you folks can help.

Have a great day all.

Lets first get power to the unit.

Sounds like your Red is 24VAC hot and connected properly to the R terminal. You now need to connect your 24VAC common wire to the C terminal to properly power the tstat. Do you have another wire than the Red Green White Yellow mentioned above?

There is a blue wire that is not connected to anything and it doesn't appear to be used. Looks like a spare.

Could be your missing common.

I hesitate to tell folks to just hook it up, so best is to follow that back to wherever and verify it is your common or hook a multimeter to it and Red to verify 24VAC.

You are missing the C common wire


From your Honeywell manual.


The T8001F, T8024F Thermostat is powered directly
from the system transformer. Batteries are not required
because setpoints are held permanently by non-volatile
memory.
Your manual

http://customer.honeywell.com/techlit/pdf/PackedLit/69-1465.pdf


Honeywells manuals are some of the best in the industry but you need to read them carefully. The wiring diagrams are also great.

The PDF link is awesome, Much more detailed than what came in the box. I needed that schematic and now I can get this thing working... Thank You ALL.

Hvac1000:

Honeywell manuals need improvement. I've even complained. Not a blip back.

Here is a perfect example from the VisonPro Install guide

0350 Heat pump compressor lockout
0 No heat pump compressor lockout
[Other options: outdoor sensor below 15, 20, 25, 30, 35, 40°F (-9.5°C to 7°C)]

0360 Heat pump auxiliary lockout
0 No heat pump auxiliary lockout
[Other options: outdoor sensor below 40, 45, 50, 55, 60°F (4.5°C to 15.5°C)]

The word outdoor sensor below is missing.

Documentation is a PAIN to write.

Glad it worked out for you.