Question about Honeywell Electronic Programmable Heat/Cool Thermostat - CT3300A100 Heater

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Honeywell dial thermostat

Stumped. Honeywell dial type wall thermometer giving no reading on face. No batteries to replace (hardwired), tripped the circuit breaker, checked furnace switch, nothing worked. Still blank.
Unit 5 years old, no a/c just gas heat. Decided to do a test drive when I noticed the problem. Worked fine last winter.
Whats going on??

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4 Suggested Answers

  • 168 Answers

SOURCE: honeywell RTH230B

Normally, you should have 5 color wires: W-White, Y-Yellow, G-Green, R-Red and C-Blue.

The Blue wire is a common from the transformer on older systems, which is probably hooked to RC terminal.

Try this: Remove the blue wire and jump the RC to RH with the red wire and you will be fine. Blue wire should not be needed with the new thermostat.

This should also be stated in the instruction manual.
Hope this helps.

Posted on Feb 03, 2008

muttandjeff
  • 359 Answers

SOURCE: Honeywell dial theromostat.

you need to check the furnace itself for , locate the 24 volt ac transformer inside the unit and see if it is fused some are some not , check to see if you have 120 volt ac in from the source and 24 volt ac out , sounds to me as if you have lost the 24 volts ac which powers the thermostat as well as the furnace pay close attention as to how you remove the wires and make a diagram and you should be able to replace it yourself , once you get it uot goto a heating supply place in your area and let them match it up and this should be a fix ya

Posted on Dec 31, 2009

shastalaker7
  • 1515 Answers

SOURCE: Our Honeywell programmable thermostat is

Good Morning, and yes you said it. Anytime a stat doesn't come on when it is set for a call for heat or cooling, the sensor on the subbase of the stat has lost its ability to sense the correct temperature. I have seen mechanical stats last as long as 25 plus years, but that's truly amazing for a digital stat to last that long. Yes, replace the thermostat. I don't know what kind of system you have, but if its a gas furnace with an a/c, the wiring will look like this. You will have terminals marked R, Red, for the 24 volt hot wire, G, Green, Y, Yellow, and W, White for heat. Going back to the red wire, it should have RC and RH on it. There will be a normally red wire connecting the 2 terminals.The Red wire coming in can connect to either one, as they are all together. The new stat will come with the new Red jumper wire attached. So, if you do have a gas heater, this is very easy to install. The only terminals you will need to use are RH to RC for the incoming red, Y, G, and W for heat. Y is for cool, and G is for fan. Very easy. Now if you have a heat-pump, they have many more terminals and can be a problem wiring them. If you have gas, forget the heat pump. I wont confuse you by going there. If it is a heat-pump, contact me in the comment box to let me know, and I can help you there also. Get a new stat at Home Depot, Lowe's Hardware, or O.S. Hardware. You want a 5 day, 2 day programmable Heating and cooling thermostat, 24 volts.It will have everything you need. See if it takes batteries for the display, they may not come with those, it will say on the box. Turn off your power to heater, so you won't short out the new one.They come in 2 sections, first the stat that just snaps on, and the subbase that is screwed to the wall. It will have the wiring terminals on it. Remove a couple of screws and loosen wires and remove. Be sure you write down how the wires go in case they used different colors, you never know. You will be all set. Store the manual in a safe place for future use. I wish you the best.
Shastalaker7
A/C, Heating, & Refrigeration Contractor.
PS, Please rate me on this :))
Happy Holidays to you and family!

Posted on Nov 23, 2010

Testimonial: "I hate spending money needlessly replacing items that may not be the problem. Thank you for confirming my suspicions."

  • 1015 Answers

SOURCE: My honeywell thermostat is asking

The first thing i would do is to make sure the t-stat is good.One easy way to do this is to remove stat cover then remove the screws that hold it to the wall. Disconnect t-stat wires making sure you note location. There should be a red and white wire for heat so put these two together and if your furnace comes on then the stat needs replaced. If it does not you need to check further to make sure you have power to your furnace.If the furnace does come on with these two wires together the furnace will run non stop. Hope this helps you. Thank you

Posted on Jan 12, 2011

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