I have a Ducane heat pump. When running in AC Mode, the outdoor fan and compressor kick off just fine. The blower fan seems to kick off as well, though it's not putting out very much air. I can feel cool air blowing out of the vent but it's a small trickle, and it's not enough to keep the house very cool. I've also noticed that the pipes are freezing over inside my outdoor unit (which I have been told is a side-effect of the blower fan not pulling its weight). I've cycled the breakers and verified that the filter is clean / new, with no improvements. One of the breakers on the box that controls the outside unit seems very flimsy, and it has been suggested that this should be changed as an electrical issue there may be preventing the blower fan from running in 'high' mode as is usually the case with AC. Is there any merit to that suggestion (i.e. an issue with the breaker could be causing the fan to run slowly) or is there a more likely problem that would cause this type of symptom?

Any help / suggestions would be appreciated. hvac air-conditioning fans heat-pump blowerac unit hail guard There are a multitude of blowers out there. car ac repair in colomboThe outside breaker you mention likely has no relation to this problem. mr slim split system air conditionerThe pipes are indeed freezing due to too little airflow. Here are the most likely causes and solutions for this: Assuming you have one of the most common PSC types (and not some other type like an ECM, slip induction, etc), then a weak run capacitor for the blower motor can cause this problem. The run capacitor for the blower should be checked with a capacitance meter and replaced if it is below 90% of the rated value. Or, if you happen to know how to use an ESR meter, then check the capacitor that way.

It is possible that it is a multi-speed motor with the wrong lead energized in the "cool" mode. Typically Red=Low, Blu=Med, Blk=High. The black lead is usually the one needed for a/c operation. Sometimes the motors wear out by having the lubricant in the bearings go dry. In this case the blower wheel will not turn effortlessly and smoothly by hand when the unit is off. If the bearings are dry, then you need a new blower motor.Since you have a heat pump, if it is a higher performance model it may have an electronic blower speed control that is supposed to automatically slow the blower when it is very cold outside to ensure an adequate warm air temp inside. Typically, this would be shunted to high speed blower mode for a/c operation, but if a control relay has failed or appropriate wire become lose, or other fan speed control failure has occurred, then the speed control could be causing the blower to run very slowly (as it would in cold weather heating operation). If you have this then you will have to determine if it has failed by temporarily bypassing it to see if the fan runs on high speed without the speed control unit inline.

Verify main power for the unit is off before proceeding with any of this work. The main power for the air handler is usually separate and in addition to the main power for the outdoor unit. **Edit: I see that Ducane air handlers offer options including both electronic blower speed controls as well as constant torque (ECM) motors. If your unit has either of these then the low speed problem may have other causes. For example, ECM motors have an electronic digital driver that is set using DIP switches or other means. An incorrect low torque setting yields low blower speed. I recommend you post the exact model number of your air handler as well as a photo of the interior showing the back end of the blower motor and the control board. A close up of any DIP switches as well as a legible photo of the schematic on the inside panel would be nice too if you want any additional comments.Browse other questions tagged hvac air-conditioning fans heat-pump blower or ask your own question.How a Furnace Works;

How It Turns Itself On and OffOften the best way to figure out what is wrong with something is to know how it is supposed to work. If you know the sequence of operations, you can pinpoint where the sequence is being disrupted. Your furnace is no exception to the rule. When your furnace is called into action by the thermostat, there is a rhyme and reason to the procedure it follows in safely turning itself on. Next time your furnace doesn't respond to the call, you will be able to see where the problem lies, and you can either decide that it is within your skills and resources to repair it, or that you need a professional HVAC technician to handle the issue for you. The following discussion can save you time and money, whether you fix the problem yourself, or end up showing the problem to your service technician. NOTE: Furnaces burn natural gas, and use electricity, normally 120 volts; both of these present hazards. As always, be sure the power is shut off to your unit before you do any work on it.

Also, never assume anything. If what you see in your home differs from what I describe here, do not guess. You could make the problem worse and ultimately more costly to repair. Firing Order: Steps in the Operation of a Modern Forced-Air FurnaceWhen the thermostat asks for heat, the furnace jumps into action, going through the steps and components below. You can see many of these components in the video. The thermostat tells the furnace to come on. The inducer motor starts up. The pressure switch confirms proper venting of the chimney. The hot-surface ignition module (if you have one, and not a spark ignitor or a pilot) begins to glow. The gas valve opens and the gas is ignited by the ignition source. The flame sensor verifies that the gas has been lit. The high-limit switch reaches its set temperature. The blower motor comes on. The furnace runs until the thermostat is satisfied and tells it to shut down. The gas valve shuts. The high-limit switch reaches its low temperature setting.

The fan shuts down. A newer furnace may have even more bells and whistles; an old furnace may have just the minimum, a gas valve and a thermocouple (like an old-fashioned flame sensor). The thermocouple or flame sensor tests whether the pilot is lit, and stops the main gas valve from opening if it is not. Of course a broken thermocouple can also stop the gas valve from opening. The ThermostatThe thermostat is where it all begins. The thermostat is really just a set of switches that open and close depending on the temperature, allowing power to flow to certain circuits in the heating and cooling system. Think of them like drawbridges that swing up and down. They are normally drawn up, but can be lowered to close the bridge and allow power to pass. When the temperature in your home drops, the thermostat drops its bridge, sending power to the furnace to let it know that heat is needed. As the room temperature rises again, the thermostat raises its bridge and shuts off the power.

For air conditioning, the thermostat works the same way but in a mirror image, closing its bridge when the house gets too warm. If the temperature in the house is lower than the temperature to which you set your thermostat, your thermostat may not be functioning as it should. You can test this by jumping (touching together) the red and white wires to your thermostat. If the furnace comes on, your thermostat is quite likely the problem. What Do the Wires in the Thermostat Do? The Inducer Motor and Fan The inducer motor and fan push exhaust up the chimney, getting rid of carbon monoxide (CO). Older systems relied solely on "natural draft" to vent these gases, but inducers have been a great addition to the furnace system. They extend the life of chimneys, and when used with pressure switches they help prevent CO poisoning. The function of the pressure switch is to verify that the inducer motor is actually pushing air up the chimney. If the chimney is blocked, for example by a bird's nest, the pressure switch shuts down the system in order to eliminate the risk of CO entering the home.

Of course the pressure switch may also shut down if the motor is old and running too slow to satisfy the switch, or the hose from the fan to the switch is pinched or broken, or the switch itself is bad. Again, a rather simple device in a complex system. The hot surface ignitor uses electrical power to heat a very fragile ceramic element, charcoal-like in appearance, to such a high temperature that natural gas or propane bursts into flame as it flows by. The hot surface ignitor is located at the orifice at the first burner port, in order to light the gas immediately as it's introduced to the port. This prevents a buildup of unburned gas in the unit. Some furnaces employ what is called spark ignition. Instead of a red-hot surface, a spark ignitor creates a series of sparks to ignite the gas. It's not important whether you have hot-surface or electronic ignition in your furnace; the important thing is that you are avoiding using a pilot light. Pilot lights waste gas; they burn gas constantly during the heating season, and some people let them burn year round.

Want to save a few dollars? Make sure you shut off the pilot on your furnace when it's not being used for the season. Just be sure you know how to relight it next year before you do. What type of ignition source do you have? Hot Surface Electronic Standing PilotSee results without voting The gas valve is basically an electronically controlled gateway. When the unit calls for heat, and the circuit board confirms that the right conditions have been met, the unit passes energy to the valve, causing it to open and release gas to be ignited by the ignitor or pilot. When the heat cycle has run its course, the energy to the valve is cut, and the valve once again shuts, cutting off the gas supply to the burners. The Flame SensorThe flame sensor is very simple, yet causes a lot of problems for homeowners. Its only job is to verify that the gas has been lit, by sensing the heat. If there's no heat, it shuts off the gas, to avoid any dangerous buildup of gas in the unit. The flame sensor is simple to fix when it goes bad or just needs some TLC.

Video: Cleaning a Flame Sensor The high-limit switch serves several purposes. First, it keeps the furnace fan from turning on until it detects that a set temperature has been reached. Otherwise, the fan would come on prematurely, and blow cold air into the house each time the thermostat asks for heat. Second, it also tells the blower how long it should continue to run before shutting off, once the thermostat has been satisfied. Otherwise, hot air remaining in the duct work and heat exchanger, after the furnace has cut off, would just go to waste. Lastly, the limit switch will turn the unit off if the heat exchanger reaches a certain high temperature, to prevent dangerous overheating. The Furnace Fan and Blower MotorHeat for us all. Now that all the sensors have been satisfied, and the limit switch tells the blower that the air is warm enough to send into the living space, it will start the air flowing. Our furnace's blower will typically use 120 volts and push anywhere from 800 to 2000 cubic feet per minute (cfm).

Most blowers require the use of a capacitor, and have a half-inch drive that hooks directly to the fan, unless you have a belt-driven motor. Tid-Bit: In the case of a malfunction, or a cut in power to the unit, it is common for the blower to turn on and run for a period of time. This may be because there is too much heat, and a cool down is called for, or there may be a build up of "bad gases" which need to be spead out or dispersed by the fan. Save Time and Money By Knowing Your FurnaceI hope this helped you to understand your heating system a bit better. Here are some troubleshooting ideas involving the parts you just read about, and here are a few more parts tips. In case of a malfunction, your furnace will usually try to restart three times. If on the third try it cannot reach successful ignition, it will go into a lockout mode for a specified amount of time, usually an hour. Resetting the power (turning it off and on) will usually reset the board and allow the unit to show you what was happening in case you missed it.