Question about Honeywell CT87B ROUND HEATING&COOLING MECHANICAL THERMOSTAT - WHITE Heater

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BLOWER FAN WONT SHUT OFF WHEN THERMOSTATE IS OFF

BLOWER FAN WONT SHUT OFF WHEN THERMOSTAT IS OFF. ALSO COOLING MODE TURN ON. I CAN PUSH CONTACTOR IN AND COMPRESSOR WILL COME ON.

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I have a honeywell blower that runs all time it won't shut off unlees I manually shut it off. How do I reset the fan limit control switch so the fan will come on only when the furnace ignitions ignites. Any suggestions.

Tx: Keith

Posted on Jan 15, 2008

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The compressor coming on when the contact is pushed is o.k. they all do that. As for the blower fan not shutting off, some brands (Payne for example) the heating fan relay is a n.c. (normally closed ) relay. so if the time delay relay or thermal link are bad or not connected, the fan will blow even when it is turned off.

Posted on Dec 18, 2007

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Why won't the compressor run


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There seems to be a problem with the wiring of the thermostat. Apparently the thermostat is calling for cool (if wired properly), but is not being satisfied. The thermostat is just a switch. When there's a call for cool, the thermostat sends 24-28 volts to the contactor (inside the condensing unit to start the compressor and outdoor fan). The indoor fan is energized through the fan relay (inside the air handler). When the temperature in the conditioned space reaches the set temperature,then the thermostat cuts the power to the contactor and it stops the compressor and outdoor fan. Check that the compressor is actually running, if not, check for 24-28 volts on the wires feeding the contactor, if there is, and the contactor isn't closing then the contactor is defective. If the contactor closes and the compressor doesn't come on, check the capacitor. If the capacitor is good then check your compressor motor. I suspect you have an improperly wired thermostat

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You can manually pushthe contactor close and the outdoor fan and compressor should start. Do this with your hand on the insulated portion of a screwdriver and take the tip of the screwdriver and push the contactor closed. The compressor and outdoor fan should start. That tells you that you have a thermostat to contactor coil issue if the t stat does not close the contactor when you call for cool.

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A/c runs and cools blower cycles with thermosatt demand but outside unit doesnt runs constant and freezes up when blower stops ? Ithink solid state blower control board is the problem ?


If you are saying the unit outside does NOT shut off with the thermostat, you need to check the contactor on the outdoor unit. The contactor may be pitted and stuck shut, not turning the unit outside off when the thermostat shuts off.

The contactor is located in the outdoor unit, the power coming into the unit is connected to it. It looks like a small 3" box and has contacts in it that shut and open with the thermostat. The contacts may be pitted or shorted and you may need to get another contactor. You should be able to see the contacts, you may have to take off a small cover on top of the contactor to see them.
If you take the contactor off, take a picture with your phone first and make a diagram of the wires so you will know where everything goes when you wire the new one in. Hope this helps. Feel free to contact me if you need more help. Mark

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Unit does not run breakers on thermostat set to cool and fan is on auto but outside unit does not run


If this is a forced air split system, you can try a couple of things.

1) Turn off furnace open blower compartment door and remove thermostat wires. put a jumper between
R and Y. Put blower door back on and restore power.
If unit turns on, your problem is with the thermostat
or thermostat wire.

2) At the outdoor unit remove the electrical panel to
get to the contactor, push in the contactor and if the unit runs you need to check for 24v between R and C
at the control board where the thermostat wires are.
If you dont have 24volts you have a transformer problem.

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