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Question posted by sissyrotondi on December 16th, 2015

My Programmable Thermostat Is Flashing 'no Signal'. Have Checked The Breakers A

'no signal' - no heat. Checked the breakers = all is well there. New batteries. What is it? Only 2 years old.

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Answer #1: Posted by TechSupport101 on December 17th, 2015 6:47 AM

TechSupport101

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Hi. See the troubleshooting section of the Owner's Manual here here https://www.helpowl.com/manuals/Honeywell/RTH6400D/76797 - do consider a reset as per the same manual as well.

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Related Honeywell RTH6400D Manual Pages

Owner's Manual - Page 1

Quick Installation Guide RTH6400 Series Programmable Thermostat 69-2210EF-03

Owner's Manual - Page 2

Call 1-800-468-1502 for the most common system We are here to help. Installation is preset for wiring assistance before returning the thermostat to match your new thermostat to the store. 69-2210EF-03 ii It is Easy Label wires and remove your old thermostat Install and wire your new thermostat Set your heating/cooling system -

Owner's Manual - Page 3

1 Turn Off Power to Heating/ Cooling System M28097 1 69-2210EF-03

Owner's Manual - Page 4

If so, see back cover for proper disposal instructions. Old thermostat Cover 69-2210EF-03 2 M28099 2 Remove Old Thermostat Remove old thermostat but leave wallplate with wires attached. Leave wallplate in place Is there a sealed tube containing mercury?

Owner's Manual - Page 6

Pull here to remove wallplate from New Thermostat Remove battery holder. Wallplate M28343 69-2210EF-03 4 4 Separate Wallplate from new thermostat.

Owner's Manual - Page 7

5 Insert Quick Reference Card Insert quick reference card into slot in back of thermostat. M2834 Thermostat M28344 5 69-2210EF-03

Owner's Manual - Page 8

holes for plaster 69-2210EF-03 6 M28345 Drill 3/16-in . 6 Mount Wallplate Mount the new wallplate using the included screws and anchors. holes for drywall Drill 3/32-in .

Owner's Manual - Page 9

M27513 Labels don't match? We are here to help. Call 1-800-468-1502 for wiring assistance. 7 69-2210EF-03 Remove metal jumper if you have both R and Rc wires. Have a Heat Pump system? See page 14. See page 21. 7 Connect Wires Simply match wire labels.

Owner's Manual - Page 10

Back of thermostat M28346 69-2210EF-03 8 8 Install Batteries Install two AA alkaline batteries.

Owner's Manual - Page 11

9 Install Thermostat onto Wallplate Install thermostat onto the wallplate on the wall. M28347 9 69-2210EF-03

Owner's Manual - Page 13

... will NOT work on page 13 to match your thermostat to provide heating. If your system type. *Heat Pump-an air conditioner that provides cooling in the summer, and also runs in reverse in the winter to your system type is: q Heat Pump* without Backup Heat q Heat Only q Cool Only Continue with advanced installation on multi...

Owner's Manual - Page 15

RTH6400 ASybsotuetmyosuertunpew thermostat Press and hold the s and FAN buttons until the screen changes (approximately 5 seconds). SETUP WIRING ASSISTANCE M28348 Press s or t to exit and save settings. Function 1 Setting 0 Done Next Press DONE to change settings. M28349 Press NEXT to advance to next function. 13 69-2210EF-03 TROUBLESHOOTING

Owner's Manual - Page 16

... central air conditioning. 1 Heat pump: Outside compressor provides both heating and cooling. 2 Heating only: Gas, oil or electric heating without central air conditioning. 3 Heating only with fan: Gas, oil or electric heating without central air conditioning. (Use this setting if you could turn the fan on and off with a fan switch on your old thermostat.) Press to display...

Owner's Manual - Page 18

... this setting if you have a gas or oil heating system (system controls fan operation). 1 Electric heat: Use this setting if you have an electric heating system (thermostat controls fan operation). SETUP WIRING Advanced Installation Guide Function 3: Heating fan control Press the s or t button to select your heating system and fan operation: NOTE: If Function 3 does not...

Owner's Manual - Page 23

Connect O wire to both O and B if you have a heat pump. Wrap B wire with electrical tape. 21 69-2210EF-03 Do not use . RTH6400 Wiring If labels do not use C,...here (see page 6). Wrap bare end of wire with electrical tape and do not match letters on the thermostat, check the chart below ). SETUP WIRING ASSISTANCE TROUBLESHOOTING M28418 If wires will be connected to O/B W.

Owner's Manual - Page 24

... it is set to acceptable change • Check Function 1: System Type to system setting make sure it is blank • Make sure fresh AA alkaline batteries are set to Cool heating and cooling equipment (see page 16). Display is set to match your to match your thermostat, please try the following suggestions. ASSISTANCE TROUBLESHOOTING...

Owner's Manual - Page 25

... system to restart safely, without damage to Cool. Make sure the temperature is set lower than the Inside temperature. • Check circuit breaker and reset if necessary. • Make sure power switch at heating & cooling system is on. • Make sure furnace door is set higher than the Inside respond temperature. • Press...

Owner's Manual - Page 26

...heating and cooling equipment (see page 14). SETUP Advanced Installation Guide Troubleshooting Heating • Check Function 1: System Type to and cooling equipment running in make sure it is set to match your cool mode heating... and cooling equipment (see page 14). WIRING ASSISTANCE TROUBLESHOOTING 69-2210EF-03 24 Check to make sure turn off...

Owner's Manual - Page 27

... Customer Care toll-free at 1-800-468-1502. WIRING ASSISTANCE TROUBLESHOOTING 25 69-2210EF-03 To save time, please remove the battery holder and note your model number and date code before calling. Battery holder Part No. 50007072-001 Cover plate assembly Part No. 50002883-001 *Use to cover marks left by...

Owner's Manual - Page 30

... 4Z9 http://DIYthermostats.honeywell.com Printed in a sealed tube. D542,677 and other patents pending. © 2008 Honeywell International Inc. 69-2210EF-03 M.S. Contact your old thermostat in the trash if it contains mercury in U.S.A.