Trouble Shooting your A/C

If your AC is not running at all.

The first thing you should do is check your electrical panel. I know this is obvious, but you would be surprised how many people pay for a service call and it is nothing more than a tripped circuit breaker or blown fuse.

Also check the 240 volt disconnect, this is usually a metal box (sometimes plastic) that should be located near the outdoor unit. We know of one homeowner who found his disconnect turned off twice in two weeks. He put up a motion detector light and found out it was some neighborhood kids just “horsing around.” He spoke to them and had no further issues.

You might also try turning the unit off completely and waiting for about five minutes before turning it back on. There are certain safeties built into modern units that will shut it down if certain conditions apply or are not met. If this occurs, you should call Stockton Mechanical or another competent contractor.

Finally, check your thermostat. If you have a blank screen you may just need batteries. Sometimes thermostats just fail, and experience has shown that some of the cheaper thermostats tend to have a shorter life than others (sometimes much shorter).Check and make sure the thermostat is set to COOL and that its desired temperature setting is at least three degrees lower than the room temperature. Bumps and accidents happen that may affect the thermostat.

When you turn the AC on and hear a click followed by a humming or buzzing sound, it is usually the fan motor attempting to start or turn without the electrical boost it normally gets from the run capacitor. Again, this should be checked and replaced as needed by a professional.

If you hear clicks but not a buzz or humming sound, it is usually the contactor. A contactor is basically a switch that engages the compressor and the outdoor fan motor. Do NOT attempt to replace this yourself as ii is usually near the capacitor which stores a significant electrical charge. Call the pros at Stockton Mechanical to replace.

What if my AC is running but not cooling?

The first thing you need to check on is proper airflow.

In Real Estate, it’s location, location, location. In Air Conditioning it’s airflow, airflow, airflow. As much as 70% of AC problems can be traced back to airflow.

Is your filter dirty?

Have you closed off some registers or blocked them with furniture?

Was your duct system correctly sized for your unit?

Do you have any leaks in your ducts?

Is your return air grill sized properly?

If there is not enough air flowing over your coil it will tend to freeze up and can actually turn into an ice block.

If there is to much air flowing over your coil, the air will not have time enough to cool properly passing over the coil.

First, check your filter. Ideally it should be changed every 1 – 3 months. If you have pets it should probably be checked and changed monthly.

Anyone that has been in the business for awhile has seen air filters clogged with an inch or more of dirt and hair. They look more like carpet than an air filter. This is not good for your system.

If your filter is in good shape or changed and you still have air that is not cool enough, call a professional like Stockton Mechanical who are experts in air flow.

Some other causes if your AC is running but not blowing cool air could be a kinked refrigerant line or a blower fan that isn’t running or a compressor that isn’t working properly. Any of these causes is reason enough to call in a pro.

It could also be possible that there is not enough refrigerant in the system. Special instruments are necessary to check this.

Another problem could be that your outdoor unit is dirty or clogged with debris such as leaves or other vegetation (cottonwood?). Your outdoor unit has a coil as well as the indoor unit. If this becomes dirty it will not operate properly causing poor system performance.

If your blower motor hums but doesn’t run (no air from the registers), you will most likely need to replace it.

Air Conditioner won’t turn off

If the thermostat is blank (no display) and has batteries, it is probably broken and will need to be replaced. This may also be caused by low air flow or by a dirty condenser that can’t evacuate enough heat outdoors. There is also the possibility that the contacts on the outdoor run relay have fused together. This can happen over time because of frequent electrical arcing that literally welds the contacts together.

AC cools unevenly

Significant temperature variations in a home are usually the result of blocked vents or registers, leaks in the ductwork, or poor insulation. This is assuming that your system was installed properly to begin with.

It is a simple fact of physics that a single system that is not zoned will have temperature variation issues if it is two story or more or if there is significant length between the AC unit and the furthest rooms.

Duct work also must be sized correctly.

If you have a single system with no zoning in a two or 3 story home or rooms far from the actual unit, you can expect to feel a temperature variation of 4 degrees or even more. Some contractors will tell you that locating the return centrally will overcome this issue but that is not true.

A perfectly designed home will be zoned as necessary or have separate systems for needed areas and even have return air grills as well as temperature sensors in each room. This of course adds to the expense of the system but is worth it if your comfort is important to you.

A more economical solution may be to have your contractor install a ductless mini split upstairs or at the opposite end of the home.

This is a small wall mounted unit that is perfect for single rooms or portions of the home that may need extra cooling or heating beyond what your main system provides.

Stockton Mechanical will be happy to discuss your options if you have this problem. They are experts in air flow, zoning and ductless minisplits.

Last but not least

The importance of properly sizing your heating and AC system.

If the system you put in is not sized properly by your contractor to begin with, you can have all kinds of problems.

If your system is to small, it will run constantly trying to keep up with rising temps and cause misery on the hottest days.

If your system is to large, it will cycle on and off constantly causing wear and tear on components, especially compressors.

Bigger is NOT always better!

Your duct work is also part of the system and can cause problems as well, some already discussed.

Bottom line: If your AC isn’t working properly, Call Stockton Mechanical at 505-629-9955 and we will make it right for you.