This page helps to walk tenants through some common Furnace and AC troubleshooting. Tenants are responsible for things like replacing thermostat batteries and furnace filters and often something simple like this is the problem. If we call in an HVAC contractor because a tenant is reporting issues and it ends up being something simple in which the tenant did not do their due diligence and it was not an actual system issue, tenants will incur the cost of the contractor. If the issue you are experiencing doesn’t appear to be one of the below, please contact us and we’ll arrange for an HVAC company to come to the property.

How a Thermostat Works

It is important that you understand the basics of how these work. Your issue may be a simple as two double AA batteries needing replaced, or that there is a schedule programmed to raise and lower the temperature and you need to change that. A copy of your thermostat manual should be available in the tenant portal (ask your landlord if that is not the case). This video talks about how thermostats work. You only need to watch through the 3:42 mark as the last part gets into smart thermostats.

Changing Thermostat Batteries

Heat or AC not coming on may be as simple as your thermostat batteries are low. Usually there is some sort of low battery indicator on the screen but not always. To get to the batteries, you have to pry off the face plate usually from the bottom or top. Please be gentle when doing this so you don’t pry the thermostat out of the wall or breakoff plastic tabs on it. See the below video for a quick demo.

Changing Furnace Filters

Furnace filters collect dust and pollen in the air and should be changed monthly (every 3 months at minimum). This will improve the quality of air in the home and makes the furnace and AC more efficient (saving you money). Furnace filters that are clogged up can restrict the air flow and cause the AC to freeze up and stop working (because not enough air is flowing over AC coils). Furnace filters are tenant responsibility to change, these come in different sizes as well so make sure you get the right size (your old one will say the size on the side). The below video talks about how to change these and what to look for in a filter. Unless you have allergy issues, the cheapest filters are sufficient and will allow for best air flow. Filters can be purchased at Walmart, Target, or any home improvement store and are pretty inexpensive. If you are in a duplex the furnace for the lower unit will be in the basement. In most cases the furnace for the upper level is also in the basement but could be in the unit itself. If you see two furnaces in the basement and don’t know which is yours, usually it will have something like “up”, “upper”, “down” or “lower” written on it with marker to denote if it is for the upper or lower unit.

Uneven Temperatures on Different Floors

If you are having issues where the upstairs is hotter in the summer then the main level, or in the winter the downstairs is colder than the upstairs, this is natural. Hot air rises, and cool air falls. You might need to adjust register vents and/or dampers in the various seasons so that rooms are getting the right amount of air flow. In the summer, you want to close the ones on the main level more so that more cool air can get pushed upstairs. In the winter you want to close down the ones on the upper level so more hot air goes to the main level and can rise naturally upstairs.

Register Vents vs Air Returns

Make sure you are adjusting register vents and not air returns. Air returns pull air from the rooms back through the furnace and heat it, where as register vents have air getting pushed out. Usually register vents have some sort of adjustment lever on them to change how much air is coming out where as air returns do not. When the furnace/ac is running, you can tell the difference by holding a piece of paper over the vent/return. If the paper sucks in it is a air return, if the paper is pushed out it is a register vent.

Dampers

Some properties in the basement have dampers in the vents that can be adjusted to raise and lower the amount of air flow running to parts of the property. You’ll see these usually in round pipes about 6in wide. Look for levers on the side. Below is image of a damper. Notice the lever on the side, when it is turned to run with the direction of the pipe is when it will let the most air through. Turning it perpendicular to the pipe will close off almost all air flow. You’ll have to determine which pipes run to which rooms to know which ones make sense to increase or decrease the air flow. It may make sense to have someone else stand near the register vent with a hand over it to determine if it is changing anything while the person in the basement adjusts the dampers.

AC Air Barely Blowing

If you are running the AC and barely any air is coming out of the vents, then it may be because your air conditioning coil is frozen up.  Your coil is located directly above your furnace and is encompassed in a metal box (see below).

The coil has all sorts of little pipes inside that get very cold and then the air blows over them to cool the air and get pushed out the vents.  If the coil freezes up, air can’t pass over it and this is why barely any air is coming out of the vents.  The below image shows what a coil looks like inside the box above the furnace.

How to know my coil is frozen for sure?

Your air conditioner has an outside unit called a condenser unit that will be square and rectangular shaped (see below diagram showing inside and outside components).

Typically if you have a frozen coil, then the lines/pipes that run into your outside condenser unit will be all frosted over (see below image).

Causes of AC Coil Freezing

Usually the issue is one of the two things:

1. You have a dirty furnace filter and this is restricting the air flow that can go over the coil. Not enough air flowing over the coil will cause it to freeze up. See the above section on checking and changing your furnace filter. If this is the case, you’ll need to change the filter and then shut the AC off on the thermostat for several hours to give it a chance to unfreeze before starting it again. You might also turn the fan to “on” instead of “auto” on the thermostat as the air blowing on it might help to unthaw it faster.
2. Your unit is low on freon. If you’ve already tried the fix for #1 and it isn’t working then please contact us and we will arrange for an HVAC contractor to come out and look at it. You’ll need to make sure to shut the AC off on the thermostat several hours before the HVAC contractor arrives as they can’t work on it or charge the freon while it is still frozen up.