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I have installed a Honeywell CT8775C, when I put it on the heat the A/C goes on!! I have checked my wiring and everything looks right? what should I do to correct it.

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You should have a minimum of four thermostet wires. The red wire goes on the R terminal. White wire on the W terminal. Green wire on the G terminal. Place the yellow wire on the Y terminal. In most cases NO other terminals are used...... IF YOU DO NOT HAVE A YELLOW WIRE...... place the blue wire on the Y terminal. This should hopefully fix it. IF NOT....See if the thermostat has a RH and a RC terminal. If so I'll bet that you put the red wire on RC ternimal. this is for airconditioning ONLY. The RH terminal is for heating ONLY. Put a small jumper wire that will connect RH & RC. Then this should solve your problem.

Posted on Mar 08, 2009

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Had new heating installed an got honeywell thermastat .weet to put heating on today for firsf time heating wont come on

If it was changed during the cooling season, the first thing I'd check would be for a jumper between the Rc and Rh terminals on the thermostat sub base. If not there, install a short jumper to power the heat side of the system. If there IS a separate wire on each of the Rc and Rh terminals, you have to check to make sure there are TWO transformers in the circuit, one for heating, one for cooling. Most new systems are NOT set up this way, but there a few dinosaurs out there. If there ARE two transformers, do NOT connect the jumper or one of the transformers will immediately burn out. If there ARE two, proceed to troubleshoot the heat side of the control circuit. Look for a secondary fuse or tiny circuit breaker, loose or broken wire on Rh, W1 on t-stat or in furnace. Then call a service tech....If you are not capable of performing the above, call the tech first.

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How to wire up a thermostat? It is a honeywell model CT 3500. There are 4 wires. Red ,Green, Black, White

Carefully look on the back of the thermostat there should be letters next to the brass screws. Red is the R terminal white is the W terminal these two work the heat directly. The green is usually a ground and it goes on the G terminal then the yellow can be the fan and goes on the Y terminal. Take your time make solid connections and be careful when stripping the little copper wire they are small and brittle so if you strip them with a knife and cut into the copper they can break upon snapping it to the base.

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Forget the wire colors and go by the terminals on the new and match on the new.


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1 Answer

Honeywell RTH230B cooling problems...

I printed out the instructions for your thermostat. It looks like you should have the following.

There should be jumper wire between Rh & Rc

Red wire to Rh or Rc whichever is easier since there is a jumper. This is the hot wire and all the thermostat does is connect to route it to the components needed for heating or cooling.

Blue wire, tape it up and don't use it. There is no spot on this thermostat for it. It is only used on thermostats that are powered by the transformer.

White wire to W. Powers the heat relay

Yellow wire to Y. Powers the cooling contactor

Green wire to G. Powers the indoor fan relay

There is a black jumper on the back of the face plate. Look at section 2.4 Setting J2 Jumper in the installation instructions. Make sure you have it in the right position for what you have. If you don't have them just google them.

Hope this helps.

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1 Answer

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Make sure red wire is on R terminal, white wire is on W terminal. Also look for a short in the thermostat wire.

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check wiring to furnace check wire hook ups on board match letters and colors sometimes installer use what ever wiring they chose on letters

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when you programed it did you go through all the setup #1-0 ,#3-0 ,#5-5 ,#12-1

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Went from Analog thermosat to a Honeywell 5000 series Digital Thermostat. Worked fine all winter. Now, when I put it on Cool it pushes out Heat. This is a Trane Heatpump.

Look to see if you have it wired correctly with the o terminal be used and then check to see if you have a jumper wire between the Y and W terminal on the Base of the tstat where you hooked all the wires up.

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the thermostat will to any temperature but will not shut off

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