Home & GardenInteriorsVentilationTroubleshooting Your Central Air Troubleshooting Your Central Air Split-system central air conditioners, used with forced air furnaces, take hot air from the house and blow it through an evaporator coil located in the top of the furnace to cool the air. The cooled air circulates throughout the house via the heat ducts then returns to the furnace as warm air to be cooled again. Central air conditioners can work for years without problems if properly maintained and serviced annually. If they aren’t working properly, call a trained technician. But before you phone, see if the problem is caused by something else. The unit stops working If you have your system inspected and cleaned annually, it should run without any trouble. However, if it stops working completely and you aren’t sure why, troubleshoot before calling a pro: Check the circuit breaker or fuse box to find out whether the unit has power. Check the fuses in the disconnect box located outside, near the condenser, to make sure there’s power.

Replace or clean the furnace filter. If the condenser coils are coated with dust or debris, use a garden hose to wash them off. If the air conditioner still won’t work, make the call. A technician may have to recharge the refrigerant. The unit won’t quit running If the air conditioner runs constantly, here’s what to do: Turn up the thermostat. If you set the thermostat a few degrees higher, you will save energy and a lot of money when it comes time to pay your electric bill. And your significant other won’t have to complain about wearing a sweater indoors. Take the cover off the condenser and find out whether anything is blocking the air flow. Vacuum the interior of the condenser, and then flush it with a garden hose. If the fan blades are bent or dirty, straighten them out and/or clean them. While the cover is off, oil the motor on older air conditioners. (Newer units are sealed and cannot be oiled.) Take off the plastic covers — there should be two — and put a couple drops of lightweight oil, such as 3-in-1, into each.

Check the furnace filter and blower to see whether they’re blocked. Use a vacuum cleaner to clean dust and dirt on or around the blower.types of central ac units Replace the filter if necessary.best air handling unit The unit freezes upshould i cover my air conditioning unit If the high pressure lines from the condenser to the furnace or the evaporator coil in the top of the furnace are iced up, then shut the system down: Either turn off the breaker in the panel or pull the disconnect switch outside at the condenser.Your system is probably low on Freon and needs to be recharged. Water pools under the evaporator When there’s water under the evaporator at the base of your furnace, the drain is probably clogged.

You can clear it, but it’s probably easier just to replace the whole thing. If you want to try clearing it, however, here’s what to do. Take off the trap, and if it’s PVC (plastic) you can cut the pipe to remove it. Pour a vinegar-water or bleach-water solution (1 to 10 parts) into the drain. That will help remove debris and algae. If you have flexible tubes, take them off and clean them by pouring the solution through them. You can also run a wire through the tube to scrape the walls. Do it gently so you don’t poke a hole. Reassemble the tubes and trap.I’ve addressed, briefly, iced up air conditioners, in the FAQ of our website at the bottom of the page, but with this problem being at the top of the list, as far as problems we run across, I wanted to address it further.  When I answer the phone, this is what I hear: “I live in Plano, Tx and my ac unit keeps freezing up” or “I live in Richardson, Tx and my air conditioner is frozen” or “I live in Allen, Tx and my a/c is icing up”.

The first and foremost thing you need to know is YOU HAVE A PROBLEM.  Your air conditioner is iced up because there is a problem.  Now, YOU want to know—”Can I fix it and save myself a service call?”.  Go check your air filter.  If you don’t know where your air filter is, or don’t know how to change it then, no, you can’t fix this problem.  I’ve seen my customers step through the ceiling in the attic too many times to suggest going into the attic (if that is where your filter is located) without knowing how to move around up there.  So, if this is the case, turn your system off and give us a call, it may not be the filter, as there are five different things that cause the air conditioning system to freeze up.  If you ARE able to get to the filter and change it, take note:  Is the filter VERY DIRTY?  I mean, clogged solid, it’s been MONTHS since anyone has even THOUGHT about the air filter, then that MAY very well be your problem.  Remove the dirty filter and put in a clean one. 

NOW this is the most important part:  You are not ready to just start that A/C back up and get to cooling.  If you’ve seen ice outside then guess what?  Your indoor evaporator coil is a solid block of ice and that baby doesn’t miraculously thaw in seconds.  It takes 3-4 hours.  Okay, so, no big deal, just put the thermostat to system “OFF”, put the fan on the thermostat to fan “ON” and go shopping, go jump in the pool if you have one.  Get out of the house and go do something to take your mind off of it for 3-4 hours.  When you get home after 3-4 hours, turn the thermostat to system “ON”, put the fan back to “AUTO” and leave again!  You don’t want to sweat to death waiting on the air conditioner to catch back up.  Which brings me to another issue I get a lot.  I’ve been to customers houses on really hot days, the a/c has been out several hours and the house is 95-100 degrees.  So is the carpet, the furniture, the drapes–all of it!  It takes TIME for all these things to slowly “give up” their heat and for the house to cool off. 

If I forget to tell my customers to give it several hours and sometimes a complete night-fall, they’re calling me in one hour saying, “Man, this thing is STILL not cooling”.    It takes time, give it time to do it’s job.  And remember, it’s especially hard to “give up” this heat in the 100 degree weather, so it takes even longer to cool down the house until the sun goes down and we get rid of some of that beating sun’s heat gain in your home.  Back to the system has a new filter, been off 3-4 hours and you’ve just restarted it.  NOW, if the system ices up again, you didn’t fix it.  You’ve got other problems.  Give us a call and let us properly diagnose it for you, it could be one of the other four problems listed below. Another common problem to cause your A/C to ice up is the refrigerant level is low.  My customers ask me all the time, “how in the world can there be ice on the air conditioner with these 100+ temperatures outside?”.  When refrigerant pressures drop, the temperature also drops due to the pressure/temperature relationship. 

When the low side pressure drops below freezing, then you have ICE.   The ice starts inside the air conditioning system, in the evaporator coil.  A lot of times people think when the ice outside has melted they can go ahead and restart their system—WRONG!  The ice begins inside, if you see ice OUTSIDE it means the inside is a SOLID BLOCK of ice and this takes 3-4 hours to completely thaw.   When I take calls in the Summer, I try to always remember to tell the customer to TURN THE SYSTEM OFF.  Which should be what happens anyway, your air conditioner isn’t cooling?  Why keep it running?  The damage caused by air conditioners left running can be very substantial.  When you notice the a/c not cooling turn it off immediately and give us a call.  Okay, back to the low refrigerant levels.  (I could go on the freeze up subject for hours).  I hear this a lot too:  “I live in McKinney, Tx and my AC needs freon every year.”  I’ve had so many people that think this is normal. 

My response is almost always the same:  Your air conditioning system is like your body, the refrigerant is like your blood, flowing around throughout your body.  You don’t have to ADD blood unless you are BLEEDING!  You  don’t go to the doctor once a year and say, “Well, it’s time for my annual blood recharging”.  Therefore, you don’t have to go to your local air conditioning company every Spring and say, “My AC needs to be recharged”.  Your air conditioning system is a sealed system and in a perfect world, you would NEVER need to have a refrigerant refill.  As we all know, this is not a perfect world, air conditioning systems LEAK and need a refrigerant recharge.  Another quote I’ve used over and over—If I add refrigerant to your system IT IS LEAKING SOMEWHERE.  Adding refrigerant is a waste of money if your leak is really large and you’re adding refrigerant once or twice a year.  Refrigerant costs are going up, especially R-22 with it’s ban in 2010, but that’s a whole other subject. 

If you have a large leak that has to be refilled every year your best bet is to have a leak detection performed.   We can find the leak with a “sniffer-type” leak detector and determine what steps need to be taken from that point.  Sometimes the leak is a place that we can repair it, sometimes the leaking piece of equipment has to be replaced. 3.  BLOWER MOTOR IS NOT OPERATING Okay, next problem that can cause a freeze-up:  The blower motor is not operating while the rest of the system is running.  If you notice the outside air conditioner is running but the indoor system is not making ANY noise, you’ve got a problem.  Turn off the system and give us a call.  This could be a couple different things that needs to be properly diagnosed by a trained technician. 4.  OUTDOOR CONTACTOR IS STUCK Next potential problem is a stuck contactor.  This is a small part on the outside unit.   If you shut your system off at the thermostat you can run outside and see that the outside unit keeps running, that’s your dead giveaway. 

So turning the thermostat doesn’t help here, it will just continue to ice up until we can arrive unless you can shut the breaker off to the outside air conditioning unit.  You can see my post in the FAQ about how to safely and properly shut off the breaker if you don’t know how.   That way, at least the system can be off and thawing until we can arrive to help you. 5.  INDOOR EVAPORATOR COIL IS DIRTY/CLOGGED This could be a whole other subject too, and I may very well blog about it later.  The most common issue that causes an evaporator coil to get dirty is for unfiltered air to get to it.  This can be caused by several factors:  Maybe the system ran for some time with NO filter, maybe the system ran with a filter that was too small and unfiltered air got past the filter, maybe the filter became VERY DIRTY and was drawn in to the system allowing unfiltered air to get by, or maybe a cheap inexpensive filter has been used that allowed dirt to get through it.  It could be any number of reasons. 

Plain and simple, if unfiltered air gets to the evaporator coil, the evaporator coil BECOMES the filter.   I hear a lot of companies advertise or telling customers that cleaning the evaporator coil is part of regular maintenance.  That would be all fine and good if cleaning the evaporator coil were an easy task that could be included in a regular maintenance cost.  To clean an evaporator coil, and to do a good job, one must first gain access to the said coil and then spend quite some time removing surface dirt from this coil.  The keyword there is surface dirt.  Keep in mind that that is all that we will be capable of removing.  Now, there are companies that will remove the entire coil, take it to a car wash or use a power wash to clean the coil and then reinstall the coil.  We did that at one time too, that is, until we realized that the removal and cleaning of the coil will cause pinhole refrigerant leaks by blowing off chunks of rust from the coil, and we became liable.  Sometimes you learn lessons the hard way, seems that’s the best way to learn them. 

Not only that, but with the labor spent removing and reinstalling an existing coil, why not just replace that coil with a new one?  It’s the same amount of labor and you’ve got a NEW coil, because the problem with surface dirt and being only able to remove the surface dirt, you are NOT able to remove the dirt that has embedded itself deep within the coil so you’re only helping a little.  Back to the dirty evaporator and filters and such.  If you are the only owner of your evaporator, have had it since it was new, and you change your filter(s) regularly with a good pleated filter, then you have no reason to have your evaporator cleaned. If you moved into your home when the equipment was several years old or especially if your home was a ever a rental property you may have a dirty evaporator coil.  Dirty evaporator coils will cause freeze ups, low air flow and low efficiency of your equipment.   Okay, that was a lot to get the point across that a dirty evaporator coil will cause freeze ups.