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Re: ice on the outside coil !
Sounds like a heat pump.
The board should have a way to set the frequency of defrost cycles.
The unit should check the temp of the coil sensor when going into defrost. If its at the correct temp., it goes into defrost mode. If not, it will go into defrost for about 30 seconds and then back into the heat mode. I would look into the sensor. It is usually located on the inside of the outside coil at the bottom. Usually has 2 wire leading to it. It will probably be wrapped in some type of insulation tape.
Good Luck and I hope this helps.
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You can start with a heat gun or good hair dryer and defrost. Upon doing this you need to locate the defrosting element and this is where your problem will more than likely be. You can use a volt ohm meter and check for resistance or open connection. Some times even a blown element will show continuity it will just be lower than normal. Just an educated guess and strong feeling this is the culprit. I certainly hope you did not toss out the defrost control board because now you have a spare. Take your time in pulling out the old element and secure the new one properly, vibration is not kind to elements.
Sounds like it may be the defrost board. The temperature switch closes when it gets cold enough and then when the board checks to see if it needs to defrost the unit goes into defrost for a set time period. Could also be that the reversing valve is sticking.
It sounds like you have a bad defrost board or defrost sensor.
Will the unit defrost on its own?
If you take the panel off and find the defrost board, there is two pins labeled test or speed up.
Take a screwdriver or something and touch these two pins together with the unit running in heating and hold it for about 10 to 15 seconds to see if it will go into defrost. If it does then the board is OK.
Next you need to check to see if you have a coil sensor by looking on the board at the wires you will see that the wires are labeled on the board. Two of the wires should be labeled either coil or sensor.
Some of the sensors are thermistors and some are switches.
If it is a switch then you can disconnect the two wires and put a jumper across the two terminals labeled coil or sensor and with the unit running in heating and touching the speed up pins together and holding it for a few seconds and if it goes into defrost you have a bad sensor.
If it is a thermistor you can’t do this because you need a certain ohms resistance across the terminals, it won‘t hurt anything if you do jump the two terminals, it just won‘t go into defrost.
If no sensor then you have a timed defrost you should see a jumper wire and some pins labeled 30 - 60 or 90 meaning minutes. If the jumper is on 90 then move it to 60 or 30 and see if this will help this board also has the speed up jumper. With the unit running in heating by touching the two pins together it should go into defrost, if not the defrost board is bad.
If the board checks out OK then you also could be low on refrigerant.
Hi, What you have hear is a faulty defrost board. You will have to take all numbers from the board, unit brand name, model#, serial# ect. when you pick one up. You can take it out but be sure you mark all wires so you know how to reinstall it. This will take care of you're problem. Sincerely, Shastalaker7
If its in the cooling mode the ice is in both places. It freezes up inside first then works its way outside just usually not easy to see the inside ice because its incased in the coil box. This could be due to a lack of airflow ie dirty filter coil or closed dampers or low on freon. If its a heat pump and in the heating mode it could be a bad defrost control, lack of airflow across the outdoor coil or low on freon.
double check your wiring. R terminal on the furnace will provide 24 volts to the t-stat. W terminal in the t-stat will send 24 volts back to the furnace W terminal to turn on the heat. G terminal in the t-stat will send power to the G terminal in the furnace when the t-stat is switched to fan on. Y terminal in the t-stat will send power to the Y terminal in the furnace which in turn will send 24 volts to the A/C outside. The C terminal in the furnace should be connected to the c terminal in the A/C outside as well as to the T-stat. Check the fuse again