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Question posted by cjf1149 on July 29th, 2014

What Is Wrong When There Is No Digit Read Out And The Ac Is Not Working?

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Answer #1: Posted by BusterDoogen on August 24th, 2014 3:16 PM

BusterDoogen

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There must be some wiring failure for the ac & thermostat to be inoperative. Go here for the wiring diagram for the thermostat.

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Related Honeywell T8400C Manual Pages

Owner's Manual - Page 1

Set Room FAN Auto On SYSTEM Cool Off Heat M18535 Em Ht Aux Ht Set Room Electronic Thermostat OWNER'S GUIDE FAN Auto On SYSTEM Cool Off Heat Em.Ht. M18539 1 69-1490 69-1490

Owner's Manual - Page 2

... setting. • Large digital display. Over 100 years of Honeywell engineering expertise went into the making of your temperature settings are held permanently in an effort to provide you to use. The ▲ and ▼ keys make it easy for batteries. Batteries are not required because your new thermostat! Congratulations on the...

Owner's Manual - Page 3

On: The fan runs continuously. In heating, the fan may start a few minutes after the heating equipment comes on the bottom of the thermostat case. Settings Setting FAN and SYSTEM Switches Fan and system settings are controlled by using FAN and SYSTEM switches located on . First set the FAN ...

Owner's Manual - Page 4

...: Normal setting for months when your home needs heating. SYSTEM Cool Off Heat Em.Ht. Off: Both heating and cooling are off. Digital display shows a flame when heating is not working properly. SYSTEM SWITCH M10274 69-1490 4 Em. Heat: Normal setting for months when your equipment has failed or is on. Ht...

Owner's Manual - Page 6

Set Room INDICATOR M18441 69-1490 6 To display the temperature setting on the digital display. The ▼ indicator points to Set when the temperature setting is displayed. 1. Displaying Temperature Setting ... displayed and to 37°C). The temperature setting and the room temperature are shown separately on the digital display, press either the ▲ or ▼ key once.

Owner's Manual - Page 7

... the temperature at night or during the day can lower your energy costs. When in the cooling mode, raising the temperature before you leave for work or school also lowers your energy costs. Set Room M18442 2. To lower the temperature setting, press the ▼ key. Set Room M18443 7 69-1490...

Owner's Manual - Page 8

... change the temperature setting, you might want to 33% depending on your home, where you live, the number of energy saving periods you leave for work or school. Energy Savings You can save energy. 69-1490 8 With this thermostat in the heating mode by raising the temperature setting during the day.

Owner's Manual - Page 10

Heating or cooling does not come on the thermostat is below 50°F (10°C). Troubleshooting Guide CAUTION To avoid possible equipment damage, do not operate cooling when outside temperature is set to Heat ...

Owner's Manual - Page 11

If you have questions concerning this thermostat, call Honeywell Customer Assistance at 1-800-468-1502, Monday-Friday, 7:00 am-5:30 pm, Central time. For service, contact your local heating and cooling contractor: 11 69-1490

Installation Instructions - Page 1

... Location Install the thermostat about 5 ft (1.5m) above the floor in these instructions carefully. hot or cold air from the sun or appliances. - Read these instructions. Installer ... a trained, experienced service technician. 4. T8400C and T8401C Electronic Thermostats INSTALLATION INSTRUCTIONS The T8400C and T8401C Thermostats provide singlestage, non-programmable temperature control for...

Installation Instructions - Page 2

... M10308 Fig. 1. Select the two mounting holes that best fit the application. 4. Fasten the decorator cover plate and the wallplate to wall. 69-1480-1 2 The T8400C Thermostat is powered through the wallplate entrance hole. 3. All wiring must comply with local electrical codes and ordinances. Mounting decorator cover plate and wallplate to the...

Installation Instructions - Page 3

... for improved air circulation and air quality. In heating, the fan is controlled directly by using an electric heat thermostat, the fan starts and stops with the cooling equipment. T8400C AND T8401C ELECTRONIC THERMOSTATS KEEP WIRING IN SHADED AREA ALTERNATE MOUNTING SCREW HOLE W Y G R C MOUNTING SCREW HOLE ALTERNATE MOUNTING SCREW HOLE WIRING ENTRANCE HOLE...

Installation Instructions - Page 4

...NOTE: M14686 In installer setup mode only, each press of the thermostat to change the setpoint several degrees. T8400C AND T8401C ELECTRONIC THERMOSTATS Slide the FAN switch in the bottom left corner of the t...temperature is 40° to 99°F (5° to turn heat or cool outputs on the digital display. To display the temperature setpoint on , the t key turns it off . Change the ...

Installation Instructions - Page 5

...NOTE: Steps 7 and 8 are available on select models. 7. When using an electric heat thermostat, the fan starts and stops with the heating equipment. Slide the FAN switch to display ... ten seconds, the heating equipment should start . Press the s key to the thermostat. T8400C AND T8401C ELECTRONIC THERMOSTATS 10. Press the s key to save all equipment responds properly to raise the temperature...