Re: BLOWER FAN WONT SHUT OFF WHEN THERMOSTATE IS OFF
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.
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Re: BLOWER FAN WONT SHUT OFF WHEN THERMOSTATE IS OFF
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.
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Multiple problems. Eliminate thermostat first. Remove face from wall and turn on breaker. If fan still runs you have a bad board or bad relay. If fan outside is running compressor should be too. These operate on same contactor. Verify you are getting 24 volts to coil side of contactor. If odf stops working and contactor remains pulled in you have a bad motor. If odf motor stops working the compressor will shut off due to overheating.
This can be for a variety of reasons. It ranges from something as simple as no supply power (blown fuse, open breaker, faulty contactor, or run capacitor) or it could be more serious as a grounded or open winding in the compressor motor. My suggestion to any novice and or person without proper tools and knowledge; First check the low voltage (24 volt control voltage) by turning on the "Fan on" switch located on the thermostat to on, not "Auto" The blower fan should come on, indicating there's 120 volt and 24 volt available. Fan doesn't come on is an indication that there's no control power. The next step would be to check for power at the transformer and fuse located in the air handler. There should be 240 volts feeding the transformer, and 24 volts coming out. The control voltage is needed to operate the thermostat (which is the switch that sends the 24 volt signal to the compressor contactor to turn the compressor on/off. This 24 volt also powers other relays and switches in the system. knowing that 24 volt is available also tells you that the problem is most likely in the condensing unit (outside, where the compressor is located). At the condensing unit you should check for 240 volt supply power. Upon finding 240 volt supply power the question now becomes whether or not the thermostat is calling for anything (cool or heat if the unit is a heat pump). There should be 24-30 volt available at the small gauge wires feeding the contactor coil. While having the thermostat set at a temperature lower than the current room temperature (in the cooling mode) the thermostat should send a 24 volt signal to close the compressor contactor and turn it on. The non-metallic end of a screwdriver can be used to depress the moveable part of the contactor. After pushing in the contactor, should the compressor start then you may only need a new contactor. It may just hum because of a faulty run capacitor or grounded or shorted internal motor windings (grounded or shorted windings are usually indicated by tripped circuit breaker and/or blown fuse). It's a good idea to have a good multi-meter and knowledge of use before attempting any repairs or diagnosis on your own. I recommend some basic knowledge of electricity before even thinking about attempting any repairs or diagnosis.
A thermostat is only a switch, nothing more. It's job is to cut on and off the cooling/heating equipment based on a preset temperature setting. It sends 24-28 volts to a contactor or relay which does the actual closing (turn on) or opening (turn off) the power to the compressor or furnace, and that's all it does. There could be a problem with the other parts of the system. When the space temperature exceeds the preset temperature the thermostat should provide 24-28 volts to the compressor contactor, to start the compressor. The "Auto-on" switch on the thermostat controls the fan only. If there isn't 24-28 volts from the thermostat to the coil of the contactor, the compressor will not operate,
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
The contactor for the compressor and outdoor fan is activated by your thermostat when you call for cool. The small coil is an electromagnet that gets 24VAC when you call for cool at the t stat. The red wire in your T stat connects to the blue (or sometimes yellow wire) in the t stat completing the 24VAC circuit and closing the contactor. The line voltage is supplied to the poutdoor fan and compressor upon the contactor closing.
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.
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
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.