San Diego sees an average of 266 days of sunshine every year. But what happens on those other days? Even the warmest of places will need heating from time to time, and San Diego is no exception.

On one of those rare, cold days, nothing feels nicer than coming home to a nice warm house. We all trust our furnace to work on command until one day, it just doesn’t. Here are a few reasons why you maybe asking yourself why is my heater not working but thermostat is.

(Quick note: We normally refer to the furnace as the heater, but in this post, we will use heater and furnace interchangeably.)

The Furnace is On, but Not Heat is Coming Out

One of our favorite features on modern furnaces are all the safety controls. Modern furnaces are better at keeping your home, and family, safe, and we couldn’t be more thankful. However, all these safety switches can cause major confusion for the average homeowner.

There are quite a few triggers that can set off a furnace’s safety switch. It’s important to remember that when a safety switch is triggered, only an HVAC professional can reset the system.

Things that can trigger a safety sensor are:

  • A furnace that’s too hot
  • Carbon monoxide leak
  • Too much built-up pressure
  • Broken or leaking gas line

When a safety switch is triggered or flipped, your thermostat will be on, but your furnace won’t be sending out any warm air.

When this happens, no matter the cause, it’s best to call an HVAC professional who can diagnose your system.

Thermostat Working, but Heater Isn’t, could it be the Gas?

A vast majority of all furnaces in the United States rely on gas to run. Chances are high that your furnace runs on natural gas. Most homes are equipped with a line that pulls in natural gas from a city line.

Homes are equipped with this line because gas powers more than the furnace. Your water heater, clothing dryer, and even stove runs on natural gas.

Your furnace needs natural gas to run.

In addition to gas, furnaces need electricity and even water to do their job. There are some jobs where all that’s needed is to have their power breaker reset.

When taking gas problems into consideration, the culprit could be a stuck gas valve. There have also been calls where the control board can’t communicate with the thermostat.

Think the problem is your gas line? If you have a gas powered stove, turn it on and see if you can get a burner to ignite. A lit burner means your gas line is fine. However, a burner that can’t turn on indicates an issue with the gas line itself.

Does Your Furnace Need Maintenance Work Done?

At ASI, we recommend two tune-ups per year. Regular tune-ups are so important because they help extend the lifetime of your system and keep your indoor air quality at healthy levels.

While conducting a furnace tune-up, your ASI HVAC tech will disassemble your system. They will then clean and inspect every piece, put the whole thing back together, and test the entire system.

This allows our techs to find any small problems before they become expensive issues.

When Was the Last Time You Changed Your Air Filter?

If there were anything we wish all homeowners could do, it’s check and change the air filter. This small part plays a big role for your furnace.

Why Is My Heater Not Working but Thermostat Is? It could be that your air filter is too full.

Also, it’s important to keep in mind that no matter the type of air filter you have, it will get clogged and need to be replaced. A full filter is a sign the filter is doing its job.

Clogged air filters can cause a number of problems. One of them being that a clogged filter blocks heat treated air from flowing through. Air will easily pass through a cleaner filter but gets stuck in an overfull one.

An overfull filter could be a reason your thermostat works, but the heater does not.

Is Your Furnace Short Cycling?

When your furnace is on, it’s running on a constant cycle. The cycle starts when your home temperature drops below the thermostat’s setting. A cycle lasts between 15 and 20 minutes. A cycle stops when the home temperature matches what is programmed in the thermostat.

A problem some heaters face is short cycling. This happens when the heater isn’t able to reach the desired temperature, or when it reaches the desired temperature too quickly.

Some other reasons your furnace will short cycle are if:

  1. The furnace itself is overheating
  2. The air filter is too dirty and too full of debris
  3. Your flame sensor isn’t working
  4. The thermostat is in the wrong spot
  5. Your Furnace is too big for your home

We all want the best San Diego has to offer, and that’s why you should call ASI, the White Glove Guys. Simply dial the number at the top of the screen or click here to schedule an appointment online.