Thermostat Showing a Red Light? Here are 7 Steps to Solve It
Is this your situation? Or at least close to it? It’s a very hot day, meaning you really need your air conditioner to be working, but there is a red light showing on your thermostat. Perhaps it’s blinking or perhaps it’s steady.
If this is what’s happening, I’ll walk you through a variety of reasons why and try to either provide you with a simple solution or tell you you need a skilled technician.
Your thermostat blinks or stays a steady red when your compressor—the outside unit of your AC—has shut down for some reason. When this happens, a signal is sent to your thermostat. However, your indoor unit doesn’t get a message and continues to run, not aware there is a problem.
So what are some of the problems that could shut your compressor down and cause it to send a message to your thermostat? And how do you get rid of that red light?
Keep reading, and I’ll tell you.
The Causes Behind Your Thermostat Showing a Red Light
Before getting into some of the diagnostic codes behind a red light on your thermostat, I’ll address some of the possible problems that led to the light.
As stated above, the most likely reason for a red light is that your compressor has shut itself off. You may not even be aware of it because you can still hear the inside part of the system running. However, eventually, you’ll notice that your home is getting warmer.
Possible Reasons for a Compressor to Stop Running
|Your compressor may stop running for one of these reasons|
|Loss of power|
|Failing or dead capacitor|
|Burned out condenser fan motor|
|Broken compressor contactor|
|Power surges and short circuits|
|High or low discharge temperature|
If your compressor isn’t running, don’t worry, it isn’t necessarily a catastrophe.
1. Loss of power
Check your circuit breaker or fuses to see if something has tripped or blown. If this is the case, it’s a simple fix to get your compressor running again.
If your compressor also has a reset button, you may want to try that as well.
That’s the simple, easy-to-fix issue. Other problems are more complex and will most likely require a pro. Here’s a list of possible issues:
2. Failing or Dead Capacitor
The capacitor is something like a battery. Depending on the type of capacitor you have, it has a store of energy that the fan in your compressor uses to start and run.
As the capacitor begins to fail, and eventually die, there’s not enough juice to run either the condenser fan or the condenser itself. At this point, your unit will probably just shut down.
If this happens, you’ll need to get your capacitor replaced as soon as possible. You don’t want to leave the situation for too long because a bad capacitor can lead to other problems.
For example, a weak capacitor could cause the condenser fan motor to work harder. If this goes on for too long the fan motor could burn out, so you could also damage your compressor.
3. Burned Out Condenser Fan Motor
As mentioned above, some situations could cause your condenser fan to burn out. One of them is the capacitor, but another is a lack of maintenance. That or wear and tear as your unit ages can lead to a burned-out motor.
4. Broken Compressor Contactor
The contactor is a heavy-duty switch that is found on the compressor unit outside. It turns the unit on and off and powers the components of your compressor.
If the contactor is broken it could result in your fan not running while the condenser itself continues to run—at least until it overheats and burns out as well.
Contactors rarely fail, but they can get dirty. Bugs and debris can clog it up and stop it from working properly, but they can be cleaned and replaced fairly cheaply if necessary. You can follow the steps in the following video but if you are not comfortable with this, please call a professional.
5. Power Surges and Short Circuits
An electrical issue anywhere in your system can cause your air conditioner to stop running. This could be because of a power surge or even old wiring.
You may be able to visually inspect some of your wiring, but you might want to call a pro for this.
6. Pressure Issues
Air conditioners have a high-pressure switch that will turn off the compressor when pressure is either too high or too low in the system. There are a number of things that can cause the pressure switch to engage.
- Dirty condenser coil
- Slow or failing fan motor
- Fan blades going in the wrong direction
- Too much refrigerant
- Blocked refrigerant lines
- Extremely high outdoor temperatures
Remember that anything that causes your compressor to stop working can lead to a red light on your thermostat.
If you have pressure issues you must turn your system off and call a technician.
7. High or Low Discharge Temperature
Your thermostat will respond to a high discharge temperature which happens when the pistons, rings, and cylinders begin to wear out and eventually heat up in the compressor. Things become so hot that the oil in the system loses its ability to lubricate.
Eventually, your compressor will shut down, and your thermostat will notify you with a red light.
Again, this needs to be addressed by a technician.
Low discharge pressure can be the result of low airflow, whether that’s from an issue with the belt or dirty filters. Your system is likely in need of serious maintenance, so a service call is probably the best idea.
What The Red Lights On Your Thermostat Mean
Each manufacturer may have its own error codes, so it’s a good idea for you to check your manual. Below are the codes for a York Stellar system.
|1 red flash||Gas valve issue||Call a technician|
|2 red flashes||High pressure||“|
|3 red flashes||High discharge temperature||“|
|4 red flashes||Low discharge temperature||“|
|5 red flashes||Defrost issues||“|
|6 red flashes||Furnace locked out||“|
|7 red flashes||Faulty ambient sensor||“|
|8 red flashes||Bad liquid line sensor||“|
As you can see from above, there are multiple reasons why your thermostat may begin flashing red
To recap here are the most common issues:
- Loss of power
- Failing or dead capacitor
- Burned out condenser fan motor
- Broken compressor contactor
- Power surges and short circuits
- Pressure issues
- High or low discharge temperature
Unfortunately, most of these will require a technician to come and diagnose and fix your air conditioner or furnace. In cases where you can look after the issue yourself, I have notated that above.
Hopefully, your issue was addressed here and we were able to answer your question.
While you’re here why not check out our related posts and guides below. Maybe we can help you with something else as well.