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Re: No heat -element is good. Heating contactor not...
1)check the heating element continuity&body resistance ok.
2)check the thermostat series with the coil connection get tripped.(relay from board damage)
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If you discover that your outdoor air conditioner and/or heat pump runs continuously even with your thermostat off and the indoor blower is off, the most probable cause is a stuck contactor. In most residential air conditioners / heat pumps, the contactor is the switch that allows voltage to your compressor and condensor fan motor; therefore, allowing them to run. The contactor allows line voltage (normally 208 - 240 volts) to pass through a set a contacts to your motor. The contacts pull in when the thermostat calls for Cooling and they "open" when the thermostat "satisfies". This is accomplished with the use of a low voltage coil. When 24 volts is applied to the coil, it creates a magnetic force that pulls the contactor in to close the contacts. When the 24 volts is removed from the coil, the magnetic force no longer exists.....a spring will force the contacts back "open" and stop the compressor and fan motor from running. The contactor is considered a wear-n-tear item as, eventually, the contacts will wear and begin to "pit". Eventually, they will either pit so severely, they will not allow enough voltage through them to operate the motors OR they may allow enough voltage and then overheat and weld themselves together. Often times you can lightly tap on the contactor and it will "free" the contacts and stop the motors. Unfortunately, once the contactor starts "sticking" it is highly likely it will stick again. Therefore, it is recommended that the contactor be replaced at first sign of sticking or when the contacts show signs of damage/overheating via a visual inspection.
Most electric furnaces use time delay relays called sequencers to turn the heating elements on and off. If your thermostat is calling for heat, the sequencer coil should get 24 volts and the contacts will close in a pre-determined order bringing on each element individually. If the sequencer coil is getting 24 volts and the elements are not heating, then one of the following issues is going on. 1. The sequencer contacts are not closing because it is defective. Therefore the heating element is never getting proper voltage (usually 208/230V) 2. The heating element may be broken. 3. The high temperature limit switch for the element may be open, not allowing proper voltage to the element, or 4. The element is not getting proper voltage because of a blown fuse, tripped breaker, or broken wire. I hope this helps!!!
Hello, check and make sure you are getting 240 volts to the contactor contacts and 24 volts to the contactor coil. If you are and the contactor does not energize than the contactor must be replaced. However, if it does energize then most likey you have a bad capacitor. If you are not getting 24 volts to the contactor coil check the thermostat wiriing for any cuts in it and make sure the connections are tight.
I would locate and check the transformer that goes from 120-24 volts to make sure it is not burned out.You can use a insulated tool or wooden dowel rod to manually engage the contactor by pushing contacts together. At least this will let you know if you have power to unit. If you have a volt meter then you can trace wiring coming into your furnace should be 120.Check transformer 120 in 24-28 out.check main power into a/c contactor should be 220-240 across feed into contactor.Good luck and thank you.
This could be caused by a couple of different things. First start by taking a voltmeter, and going across the 24 volt connections. You should read 24 volts. If this is not the case then you should ensure the thermostat is calling, and that you have 24 volts at the thermostat. If you have power at R, ensure you also have power at Y. If there is no power, it is most likely your transformer.
If you have 24 volts at the contactor, turn the power to the unit off, remove the 24 volt wires, and using an ohmeter, check the resistance of the contactor coil. (Where you remove the wires from) You should get a measurable reading. OL means the coil is broken, while 0 means the coil is shorted, either way the contactor will need to be replaced. If after taking this reading, all is still good (as far as testing), replace the 24 volt wires, and inspect the contacts to ensure no ants or bugs got in there. I have seen many insects stop a contactor. If you find any bugs, clean out, and you should be fine. REMEMBER that you need to have the power off when you are removing, or physically touching the contactor.
Hope this helps
if you have voltage to bstr. contactor coil and contactor is not pulling in the coil must be bad on the contactor. try pushing in thecont. manually to see it is not bound up mechcanically, if you can do that replace bstr cont. because the coil is open. dont forget to vote, monomoy
Check and find out if you have 24 volts across the terminals for the coil of the contactor. If you have 24 volts across the terminals and the contactor does not pull in change the contactor with one of the same ratting. If you do not have 24 volts across the terminals for the contactor coil your problem in in the 24 volt circuit. Possible that the thermostat is not sending power to the contactor through the "Y" terminal.
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