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Heat/AC Fan not working

When I turn on the heat or the a/c, I can hear them running, but nothing is coming out of the vents.  Even when I just turn the thermostat to "fan," nothing comes out, which leads me to believe it's the fan...why would it stop working and who is the best person to call?

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You are probably right. You indoor fan is bad.They are very easy to change and anyone with mechanical knowledge can do. I would get a ac mechanic that I know and trust to check it out because there are several reason that could cause the fan not to run. The worst thing would be a bad motor and they cost about $75. A good electrician could check it.

Posted on Nov 02, 2008

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Coleman Evcon Eb15b we replaced thermostat last night so that wasn't it when. Put in auto for heat u can hear a click. See where and feel it heating up tgen u hear. Another. Click and nothing even the heat...


if you turn on heat and no fan comes on, the electric will over heat and trigger high limit switch. the switch either self resets after it cools for a while or needs manual reset. read directions on thermostat for electric heat. energizes fan at same time as heat on calling from stat.

Nov 15, 2014 | Air Conditioners

Tip

Why your unit is freezing up.


To understand why your AC or heat pump is freezing up, it helps to know how your system works.

There are 7 major parts to an AC system, 9 with a heat pump.

1 - Condenser/heat pump (The outdoor unit)
2 - Air Handler (the indoor unit unless the system is a package unit, then all is outside in one system. The air handler is usually found under the home, in an attic, or in a closet.)

In the condenser are the following major parts.

3 - Compressor
4 - Condenser coil
5 - Condenser fan
6 - (HPs only) reversing valve

In the air handler are the following major parts.

7 - Blower motor
8 - Evaporator coil
9 - (HPs only) electric heat strips

Some systems known as "dual fuel systems" use another heat source in place of the heat strips, usually a gas furnace. I will address gas furnaces in another post.

When an air conditioner is operating properly several things are taking place.

1 - The compressor is compressing or "pumping" refrigerant through the system.

2 - through changes in pressure, the refrigerant makes the evaporator coil get very cold, and the condenser coil gets very hot.

3 - The blower motor/fan circulates air across the evaporator coils, as the room temperature air (Also known as "indoor ambient") goes through the cold coil, it exits, cooled approximately 15 to 20 degrees cooler than when it entered. (In a ducted system, the blower is also the fan that circulates the air throughout the home.)

4 - The condenser fan circulates air across the condenser coils. As the outdoor air goes through the condenser coil, it removes heat from the coils that are very hot. This in turn removes heat from the refrigerant so it can run its cycle again, and through pressure changes, cool the evap coil.

5 - With a heat pump, the reversing valve reverses the flow of refrigerant in the condenser and evaporator coils.
In AC mode, the evaporator coils get cold, and the condenser coils get hot. But in heat mode, the evaporator gets very hot, and the condenser very cold.

Now, whichever coil is getting cold will freeze up if there is inadequate air flow across the coil, as the refrigerant in it is far below freezing, and there is not enough airflow to keep the humidity in the air from freezing on the coil.

Things that can cause poor airflow are,

1 - Dirty/clogged coils
2 - dirty/clogged filter (will only effect evaporator coil)
3 - Closed/blocked vents (will only effect evaporator coil)
4 - Malfunctioning or dirty fan

Low refrigerant will also cause a coil to freeze up, reduce efficiency and cause the system to run for long periods of time. Not to mention, shortening the life of the unit.

With a heat pump, in heat mode only, the condenser (outdoor) coil will routinely begin to freeze up in cold temperatures. This is due to the fact that the refrigerant is below freezing, and the cold outdoor ambient temp is not warm enough to keep the condensation in the air from freezing on the coil.

Note, a properly working AC should never freeze up.

A heat pump is equipped with defrost controls to prevent ice buildup.
Some are controlled by timers, some by temp.

When a HP is going into defrost mode, the condenser fan shuts down, the reversing valve reverses the flow of refrigerant and the once cold condenser coil now gets very hot, defrosting the coil. (Many people have said this process sounds like the unit is coming apart, or about to explode and are frightened by the "smoke" which is really just steam from melting ice that comes off the unit.)

During defrost mode, the secondary or "auxiliary" heat comes on to ensure that you are still getting warm air from the vents. (Again, this can be electric heat strips or a dual fuel system)

If you are experiencing cold air from the vents during defrost, that means your auxiliary heat is malfunctioning.

The auxiliary heat is used for three purposes.

1 - during defrost mode to maintain warm airflow (automatic)
2 - when the HP cannot maintain the set temp due to extreme outdoor temps. It comes on when the indoor temp drops several degrees below the set temp on the thermostat (automatic)
3 - For emergency heat source when the HP is not working. (Manual)

To recap....

Iced up coils?

Poor airflow
low refrigerant
Malfunctioning fan
failing defrost system


There are two things that can be done in a pinch to help de-ice frozen coils. This may get you by until the repairman can get there, or you can fix the system if you are a do-it-yourselfer.

HPs frozen outdoor coil in heat mode, not going into defrost?

Cover most of the vents, and turn the system onto cooling mode until the outdoor coil is thawed. then uncover vents and return to heat, or emergency heat. (this usually takes 15 min or less)

Frozen coils in AC mode with a heat pump?
Turn the system to heat with the thermostat on just high enough to get the system to come on. (again, usually takes 15 min or less to thaw.)

AC only, with frozen evap coils? (this can sometimes be seen frozen all the way outside to the compressor on the copper lines.)

Turn the system off, and the fan switch from "auto" to on".
This will usually defrost the coils within 1 to 2 hours.
(If your system has the furnace in line before the evap coil, turn the system to heat, and the furnace will defrost the coil within minutes.)



on Dec 25, 2008 | Carrier XHB123D X/Y Series Heat/Cool Air...

1 Answer

Fan will not go off and nothing else will work


If this is a gas heater, the problem is likely either a tripped flame roll out switch or limit switch. The issue here is that if the limits are tripped, there could be a very serious issue. There could be a bad switch, but there also could be a plugged flue, or a cracked heat exchanger. Either way it is definately worth getting this checked by a professional Serious safety issues could easily be the issue.

Apr 08, 2014 | Air Conditioners

1 Answer

5 ton goodman package unit


I guess this is a heat pump unit, check the change over valve in the gas circuit, sounds like the solenoid on the valve is burnt out

Mar 24, 2014 | Air Conditioners

1 Answer

My furnace works on ac and blows on ac but on heat it does not blow but i hear a humming sound coming from the furnace


Most furnace operating on Oil or gas will heat the combustion chamber before starting fan to prevent cold air draft at start-up, can last a minute or two. Eiter the main flame does not come on or the chamber thermostat have fail. Try to modify fan option on room thermostat from auto to on. Cold air coming out: burner problem or no more oil or gas, warm air: burning chamber thermostat problem, leave room thermostat fan option to on until repair.

Jan 02, 2014 | Comfortmaker Air Conditioners

1 Answer

Dometic AC that the fan shuts off but the compressor keeps running


call dometic dealer. I hear they have a bad circuit board that is replaced.

Jun 02, 2009 | Dometic Rooftop RV Air Conditioner

1 Answer

Gas Furnace is not heating anymore.


the fan you hear come on at a call for heat is most likely just the inducer motor. the click you hear is probably the relay for the hot surface ignitor which should glow red, then in turn ignite the main burners. your going to have to determine if the ignitor is coming on. if it isnt the ignitor is bad and will need to be replaced. if it comes on and than shuts off after a few seconds the ifc board is probably at fault

Apr 09, 2009 | Air Conditioners

1 Answer

AC Compressor running outside but no air coming out of inside vents.


Can you say, WOw, Icould've had a v-8 moment! I think you answered your own question or you are not far from the answer. (let me direct you, either the thermostat or the little door on the duct going to your room! Thank-you-very-much!

Aug 01, 2008 | Carrier XHB123D X/Y Series Heat/Cool Air...

1 Answer

I have an amana package system heat pump model number phb30c02e , sometimes the indoor blower will not kick on thus making no air come in the home at all throught the vents, i tried a new copasitor and ...


Sometimes the thermostat can have a burnt place in the fan contacts. This stops the interior fan motor because the compressor wiring is not interconnected to the interior fan. The compressor command is the yellow wire. The interior fan command arrives from the thermostat on the green wire. Check the green wire for delivering 24 volts AC to the fan relay.

During heat, the heat is electrically interconnected with the interior fan. Thus, if the thermostat is bad, the fan will work properly during heating. I know July is a bad time to turn the heat on, but this is a method to see if the interior fan works properly and is not getting the proper command during cooling.

Jul 24, 2008 | Amana Air Conditioners

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