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Hunter "Just Right" Digital A/C Thermostat Installation Guide
Instructions for replacing an analog mercury thermostat with a Hunter 42999B digital air conditioner thermostat.

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This guide was specifically written to assist owners of the Hunter "Just Right" 42999B A/C thermostat in removing an old analog mercury thermostat and installing the new Hunter digital unit in its place. Please remember to turn off the power to your home before proceeding and take all possible safety precautions. I am not a professional. I take no responsibility for damages or injuries to your person, property or pets. Please proceed with caution and/or consult a professional.
Old Honeywell Thermostat
Honeywell Cover Removed
New Digital Thermostat
The old Honeywell brand analog mercury A/C thermostat pictured above had become inaccurate after many years of use.

To replace it, I purchased a Hunter brand "Just Right" 42999B digital electronic HVAC thermostat for about $28.

Some of the features of this new air conditioner thermostat include a digitally accurate thermometer, a filter change indicator, soft touch buttons, and a large LCD screen.

The Hunter "Just Right" (model 42999 & 42999B) thermostat is compatible with most 24 volt or 24 millivolt heating and air conditioning systems such as gas/electric/oil furnaces, boilers, air conditioners, and hot water heaters.

I started the installation process by popping off the plastic cover on the Honeywell thermostat and removing the two screws holding the interior part of the unit to the wall.

Hunter Just Right 42999
Abbreviated Instructions
Features & Benefits
With the old Honeywell thermostat hanging from the wall by its wires, I continued to the next step by labeling the wires with the stickers included by Hunter.

The letters "G", "W", "Y", "Rh", and "Rc" were stamped on the rear of the old Honeywell thermostat which made it easy to affix the corresponding stickers on the correct wires.

Compatibility List
Brands Replaced
Buttons & Functions
Then I unscrewed the wires from the Honeywell thermostat, discarded it, pulled the wires through the hole in the new Hunter base plate and secured it to the wall with the two included screws.
Shipping Form $27.80
Front of New Thermostat
Electrical Connections
The stickers on the wires made the task of screwing in the connections on the new thermostat an easy job.

Make sure that the bare ends of the wires are clear of each other to avoid an electrical short.

Hunter Circuit Board
Mercury Thermometer Switch
Lower Screw
The last few steps are to pop the Hunter face plate on to the base plate, install two AA batteries, and turn the home's power back on.

I set the "Fan" switch to "Auto" and the "System" switch to "Cool".

After a few seconds, I heard a faint click and the air conditioner began to blow out cool air.

Old Thermostat Removed
Wires On Rear of Honeywell
Wires Labeled With Stickers
Since installing the Hunter digital thermostat, it has been much easier to keep our air conditioner set to a consistent temperature.

Our power bill has also declined slightly since we're able to accurately raise or lower the temperature setting when leaving or returning to the house.

Wires Pulled Through Hunter
New Base Plate Attached
Wires Secured To Terminals
Face Plate Popped On
Auto Fan - A/C On
2 AA Batteries Installed
For more, check out the following related links: Air Conditioner Capacitor Replacement Guide, Leaking Refrigerator Repair, Toilet Water Supply Valve Replacement Guide, Kenmore Electric Range 220V Power Connection Repair Guide, HVAC Air Handler Evaporator Coils Cleaning Guide, A/C Air Handler Condensate Drain Pipe Cleaning Guide, and the Sticky Door Lock Repair Guide.
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