If your Pro1 T705 is not turning on the heat or air conditioning, start with its batteries, system mode, fan setting and temperature setpoint. A flashing HEAT ON or COOL ON indicator can also mean the thermostat is observing its five-minute compressor delay—not that it has failed. The checks below cover what the T705 manuals document and when to stop and call a qualified HVAC technician.
Start with the display and batteries
If the low-battery icon appears, replace the batteries with two AA alkaline batteries. The Pro1 T705 Operation Manual (Rev. 1751, 2017) warns that low batteries may leave heating and cooling inoperable. The icon alone does not mean the thermostat has failed. See the Pro1 T705 Operation Manual.
If the screen is blank or the thermostat does not respond, the manuals reviewed do not provide a complete blank-screen fault tree. Do not assume a particular reset or wiring change will fix it; seek manufacturer support or a qualified technician if replacing low batteries does not resolve the issue.
Check mode, fan and setpoint
- System switch: Select HEAT for heating or COOL for air conditioning. OFF disables both.
- Fan switch: ON runs the fan continuously; AUTO runs it with heating or cooling operation.
- Setpoint: Use the plus or minus buttons to set the desired temperature. For heating, the setpoint must call for heat; for cooling, it must call for cooling.
These controls and their operation are described in the T705 Operation Manual.
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- Programmable Thermostat
- Single Stage
- 1H / 1C
- Supersedes / Replaces: THT3021 THT03021 THT-3021 T-705 , TP-P-705 VIVE , 662766469912 , 662766590425 , Comfort Thermostats.
Wait if HEAT ON or COOL ON is flashing
The Operation Manual says a flashing HEAT ON or COOL ON indicator means the compressor delay feature is active. The compressor remains off until the documented five-minute delay has elapsed. Wait for that period rather than treating the flashing indicator as a repair instruction or performing a reset.
The same manual cautions: “Do not operate the cooling system if the outdoor temperature is below 50 ˚F (10 ˚C) to prevent possible compressor damage.” This is the T705 manual’s instruction, not a universal HVAC rule.
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- Single stage
- 1 heat 1 cool
- 5/1/1 programmable
- Battery powered or hardwired
- 4 sq. inch display with blue backlighting
What FILT means and how to clear it
FILT is a filter-change reminder if the installer enabled that feature. Change the HVAC system’s filter using the size required by the equipment, then hold the specified second button from the top-left side of the thermostat for three seconds to reset the reminder. The T705 installation manual does not state a filter size, so check the equipment documentation or existing filter rather than guessing. See the Pro1 T705 Installation Manual.
Check whether the T705 supports your HVAC system
The T705 installation guide lists these applications as supported:
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- SINGLE STAGE 1 HEAT/1 COOL HVAC THERMOSTAT: Designed for conventional gas or electric systems requiring simple, dependable non-programmable temperature control in residential or light commercial settings
- LARGE 4 SQ. IN. DISPLAY WITH BLUE BACKLIGHT: Easy-to-read screen with glow-in-the-dark button provides enhanced visibility and usability for all-day comfort management
- EASY CONFIGURATION WITH GAS OR ELECTRIC COMPATIBILITY: Offers selectable power via battery or 24V and includes separate swing adjustments for both heating and cooling operations
- FAST INSTALLATION WITH UNIVERSAL SUB-BASE DESIGN: Simple setup with color-coded terminal blocks and flexible mounting options on wall surfaces or junction boxes
- PERFORMANCE-ENHANCING FEATURES: Includes 5-minute compressor delay, room temperature calibration, and swing settings to fine-tune HVAC behavior
- Gas or oil heat
- Electric furnaces
- Heat pumps without auxiliary or emergency heat
- Heat-only and cool-only systems
- Millivolt systems
It lists heat pumps with auxiliary or emergency heat and multistage systems as unsupported. Confirm the actual equipment and wiring against the installation documentation; wire color alone does not establish compatibility.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When to stop troubleshooting
The available manuals explain the basic controls and certain indicators, but do not provide a comprehensive error-code table or a diagnostic sequence for every blank-screen, unresponsive-system or internal thermostat fault. For persistent problems or uncertain wiring, contact Pro1 support or a qualified HVAC technician. Do not open the thermostat or alter wiring as a casual troubleshooting step: the installation manual warns that failing to disconnect power before installation work can cause electric shock or equipment damage.
The Operation Manual’s 2017 revision lists Pro1 support at 888-776-1427, Monday through Friday, 9 a.m. to 6 p.m. Eastern. Because those contact details come from an older manual revision, verify them before relying on them.
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