Honeywell Thermostat Pro Series Not Cooling [Fixed]

If you are dealing with a honeywell thermostat that is not cooling, chances are the problem is with the cooling system and not the thermostat itself. If your honeywell is not showing the cooling option that’s a different issue and we have covered that problem in a separate guide which you read here.

However if you can see the cooling option on your thermostat but your system won’t just cool, the problem can be caused by a few known issues that we’ll be discussing shortly in this guide.

Lets dive straight into the causes of this problem and how it can be fixed

Possible reasons for a honeywell pro series thermostat not cooling

Power issueCheck outdoor unit  if its working
Bad CapacitorReplace capacitor
Locking CompressorInstall a hard start kit
Bad Condenser fan motorReplace fan motor
Clogged evaporator coilHave evaporator coil cleaned
Plugged up condenser unitClean condenser unit
Dirty air filterReplace air filters
Bad thermostatReplace thermostat
High outdoor temperatureTurn AC early enough
Leaking/ Low refrigerantHave system recharged 
Leaks in the ductsSeal off broken or leaking ducts

Power Issue

A good place to start is to check if the outdoor condenser unit is running at all. Turn on cooling on your thermostat and check if the outdoor unit is running. If it’s not you may have tripped the circuit breaker. 

Disconnected power supply can prevent the Honeywell ProSeries thermostat from functioning properly and cause cooling issues. It’s important to ensure that the thermostat is receiving consistent power to operate the cooling system effectively.

To troubleshoot this issue:

  • Check if there is a power outage or any electrical issues in your home. Verify that other electrical devices are functioning properly.
  • If there is a power outage, wait for the power to be restored, and check if the cooling resumes.
  • Inspect the circuit breaker or fuse box associated with the thermostat. Make sure the breaker is in the “ON” position or replace any blown fuses.
  • If the thermostat is battery-powered, check the battery status and replace the batteries if necessary.
  • Ensure the Thermostat is Properly Connected to the Power Source:
  • Sometimes, cooling issues can arise if the Honeywell ProSeries thermostat is not correctly connected to the power source. Loose connections or faulty wiring can disrupt the power supply and impact the cooling functionality.

Read also: Honeywell Thermostat Not Working After Battery Change [Fixed]

Bad Capacitor

 Another reason your honeywell is not cooling your home is that you have a bad AC capacitor. Nowadays ACs are equipped with duo capacitors that power both the fan motor and the compressor. 

When the part that powers the compressor dies, the fan can continue running with the compressor won’t work.

The way there won’t be cooling and it is just as good as having the fan inside running without cooling.

If you are a DIY person you can go an extra mile and open  the condenser unit  to test the capacitor for continuity. Just remember to take safety precautions such as turning off the power to your unit and discharging the capacitor before touching it.

Sometimes you can easily tell when the capacitor is dead  if it has a bulged top.

Dead capacitors can be easily and cheaply replaced online, just make sure to check the model of the capacitor before ordering a replacement.

Compressor Locking 

There are times when the capacitor is working without any problems and the fan is spinning but the  compressor is not running. 

This is also known as compressor lock out. This is common on old systems and the best you can do is to consider getting a new unit.

However, if buying a new unit is  not an option you can try getting a hard start kit to try and keep the compressor running. But not that this will only help the compressor for about a year or  two and the problem will still come back.

Read also: How to troubleshoot a problematic white rodgers thermostat

Bad condenser fan motor

When you have a bad condenser fan motor, it can  seize up and stop spinning even though you can hear the  compressor running. This is also a possible reason your honeywell ac is not cooling.

When you are experiencing this problem, there is little that can be done besides replacing the fan motor. 

Even oiling up the motor won’t fix the problem. So I recommend you consider  replacing the entire  the condenser fan motor.

Read also: Honeywell Thermostat Blowing Cold Air on Heat Setting [Fixed]

Dirty air filter

Another common  problem that prevents a honeywell thermostat for cooling is dirty air filters .Air filter screens out dirty and other particles from getting to the evaporator coil and eventually into your home.

When they become dirty and clogged, they will restrict airflow and hence prevent cooling for your home.

Government recommends that you replace your HVAC air filter 1-2 months of use. This will not only improve the quality of air but also ensure that your HVAC system keeps running in optimal condition.

Plugged evaporator coil.

A plugged evaporator coil can also be the reason your pro series is not cooling. Even with a clean filter overtime, the coil can get plugged up with dirt.

 Once that gets plugged up enough it starts to restrict the airflow which  decreases how well it cools your house and if it gets plugged up enough that coil might start to freeze over so if you see any ice buildup that may be part of the problem.

Unfortunately cleaning in a coil usually is a pain in the butt! They are typically pretty hard to get to.  You have to take apart the plenum,  the sheet metal that surrounds that coil. 

I would say mostly  the best option is to call the duct cleaning company and just have them  clean that  coil for you.

Plugged up condenser coil

A condenser coil is that unit outside. It   sucks air in from the sides and then exhausts it from the top. Basically the way it works is all the heat that it collects from inside the house it’s going to be rejecting it from up.

If the coil is super dirty with grass dirt cottonwoods, seeds and whatever else then that will restrict the airflow and causethe unit not to cool as well.

Read also: Honeywell Thermostat Keeps Going Up To 85 Degrees [Causes + Fix]

Even if the condenser looks clean from the outside it could be dirty inside between the fins. In other words, if you haven’t washed it in a while, try cleaning it. To do this task you only need a hose and supply of water, it’s pretty  easy.

Just make sure you turn off the power before removing the grills from the fans for your safety. 

Bad thermostat

Another cause for the problem is  a bad or malfunctioning thermostat . When your honeywell thermostat itself has a  problem, it could be the reason it is not cooling. 

A bad thermostat may sometimes be showing you the wrong temperature or it doesn’t turn the air conditioner on when it’s supposed to. 

When you are lucky, sometimes changing the batteries if your thermostat has batteries is all that’s needed. But in some cases you have to replace the thermostat.

So one trick to find out if that thermostat is the one that’s the problem or not  is to simply bypass the thermostat by taking it off the wall and putting a jumper wire between Y and R to see if the air conditioner will turn.  See the video below on how to do this:

High outdoor temperature

When it’s really hot outside and you simply let the house get too hot before you turn on your thermostat for cooling  you may feel likeI it is not cooling.  

For example if  it’s 110 degrees outside and you wait until it’s 90 in the house before you  turn the AC on,  your  air conditioner is not going to  catch up probably the whole entire day and it’ll take it the whole night to finally get down to that temperature where you  set it to.

Read also: How To Change a Honeywell Thermostat From Celsius to Fahrenheit In Seconds

 If you set it to 70 when  really hot outside most air conditioners will maintain that  set temperature but they will struggle to decrease it.  even if your air conditioner is running properly and there’s no problems with it.

So high outdoor temperatures do affect the cooling of your system, make sure you turn on your air conditioner early during heat waves.

Low refrigerant

Is that the unit is low on refrigerant that’s a pretty bad problem to have this is not something that a homeowner can fix themselves so if the unit is low on refrigerant

 This is not something that should be refilled every couple of years. The air conditioner is a permanently sealed system which means whatever refrigerant or freon is in there that should stay in there for the life of the unit whether it be 20 or 30 years.

Read also:Honeywell Thermostat Not Blowing Cold Air [Fixed]

  If you’re adding something to it that means your unit does have a leak and it’s leaking out somewhere.

There are  two things you can try to cheque yourself  to see if it potentially  has a problem with refrigerant;

1)  Look at the suction line.  That’s going to be the thicker copper line going through a uni. there’s usually a thin line and the thicker one,  the one that’s insulated is going to be a suction line.

When that AC is running under normal conditions that suction line is going to be sweating or condensing.  (You should see little water droplets on it.)  If it’s frozen or dry then that could mean that your unit is low on refrigerant. 

2) Check  the temperatures in your return and supply duct and see what kind of a temperature difference (also known as delta) you have between the two it should be between 15 and 20 degrees.

If you believe your  system is low on the refrigerant, you are going to need to call pros to take a look and possibly charge it.

Leaks in the Ducts

Sometimes there will be a crack in the ductwork especially where the ceilings  are or maybe they get  disconnected altogether.

Read also:

This  often happens  in attics especially with those flexible duct works.  Sometimes they get either ripped or somehow disconnected and it’s literally just lopsided air and air blowing into the attic and cooling down your attic instead of blowing into your home which is not really helping you.

But of course if you have a situation like that where here is air escaping then of course that will not properly cool the house down so inspecting all your ducts or at least everything that you can see and get to is what I advice doing especially the supply duct,  the one that’s pumping out the cold 

Final thoughts

 There are still many other reasons your honey ac system is not cooling but the ones we have looked at in this troubleshooting guide are among the most common ones. If you have managed to fix the problem after going through these tips, congrats! If not, it wouldn’t be a bad idea to also reach out to Honeywell customer support for assistance.


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