So your ac is not turning on and you want to try troubleshooting and repairing it. So before calling a technician you should check and repair these minor problems in your ac unit.
I have been repairing AC for almost 6years now and I know what are the most common problems that occur in an AC unit. Most of the time these are not even a big problem and you ended up paying for the technician's visit.
So In this article, I have listed all the possible reasons why your ac won't turn ON and the DIY solutions. And trust me this guide can save you a lot of bucks.
Reason No #1: Your Thermostat Is Bad Or Malfunctioning
The first place you want to start is your thermostat. Especially if you don't feel any air coming from your vents or if you recently replaced your thermostat. Then there's a chance that something is wrong with the thermostat.
Also if you have a programmable thermostat then that program in the background might be the thing that's messing with your ac. You can try bypassing the thermostat to check if it’s really the problem. You’ll just need a jumper cable.
First, you need to take off your thermostat and then try jumping for the fan. You’ll need to put one end of the cable to the R and the other to G.
If your furnace fan starts you’ll hear it running then your thermostat has malfunctioned or gone bad. After jumping for the fan make sure to go near the furnace to hear the fan sound.
Because sometimes your ac is set up in a way so that you don’t hear fan noises. Just a little about the wiring and thermostat terminal.
- G = Fan
- Y= Cooling
- W= Heating
- R= Power
- Rc= Power to Cooling
- Rh= Power to Heating
- C= Common
Another important thing to note is if you have Rh and Rc or just R and Rc. So you must know that you have to have a jumper in between R and Rc. Since R is power and Rc is Power to cooling.
If you do not have that jumper in there your ac will not work. So a lot of times people will put in a new thermostat and they won't put that jumper in there. And they do this when it's furnace season and by the time ac season comes around nothing works.
I have a full tutorial on How To Check And Bypass Your Thermostat Do Check It Out
Reason No #2: You Have A Tripped Breaker Panel
Now if nothing is working then you need to check your breaker panel and see if that breaker is tripped or not. Most of the breaker panels will be labeled and you can find out which breaker is connected to which unit.
The furnace breaker is going to be 120 volts so it's going to be a single breaker. Since ac breakers are 240 volts there will be a two-pole breaker it'll either be two small breakers connected together or it'll just be one big handle.
So if a breaker is tripped it'll be in the middle position. A tripped breaker is very easy to find and you can easily reset it and everything will work normally.
Reason No #3: Your Furnace Control Board Fuse Is Burnt Out
Now you need to check the control board fuse. To do that first you need to remove both the doors of the furnace. And then find the control board fuse. After finding the fuse you need to check if the fuse is burnt or not.
If it’s burnt then you need to replace it. But the thing is most likely that fuse burnt out for a reason that means something is going on. There's probably a short somewhere most likely at the ac unit at the wires.
Maybe there are some bare wires that might shoot up. So most likely what will happen is you’ll replace the fuse and turn on the whole unit and it’ll trip immediately.
So you need to find what’s causing the trip. You can do that at the control board. The Control board has the same terminals and wires as the thermostat i.e.
- G = Fan
- Y= Cooling
- W= Heating
- R= Power
- Rc= Power to Cooling
- Rh= Power to Heating
- C= Common
So what you’ll need to do is disconnect all the wires and put them back one by one. First, do it for ac then for the fan, and at last for the heating. This way you can easily find what’s causing the trip.
Reason No #4: Your Blower Motor Is Burnt Out
After checking the fuse and if it’s not the problem then you need to check your furnace blower motor. Just turn off your furnace power switch reach into your blower motor and try to give that wheel a spin. If it's very crunchy feels like it's seized up in that case you will need to replace your blower motor.
Reason No #5: You Have A Dirty Furnace Filter
The most neglected yet common problem people have for furnaces and ac is a very plugged-up filter. Most of the time your filter will be located at the side of the furnace on the return ductwork.
You need to check the filter every month or two and see if it’s dirty or not. If it’s dirty and plugged up then you need to replace it. The plugged-up filter may be causing many ac problems.
Reason No #6: Your AC Contractor Has Gone Bad
The next thing you need to check is your contractor that is located inside the condenser unit. To check the contractor you need to remove the side panel of the contractor.
So the way the contractor works is it has coils on the sides (24volt) and that coil is connected to the thermostats wires that come from the furnace.
When the thermostat calls for cooling the plunger in the contractor pulls in and those contacts meet those metal plates on either end and that lets the 240 volts through.
Once in a while what will happen is some ants or a ladybug or some other insects will get in between those contacts and when it tries to pull in it gets stuck because of that ant or whatever is jammed in between it. In that case, disconnect all power and just pluck that thing out and you should be good to go.
The first test you want to do is with the power on very carefully press the plunger in and see what happens. When you're doing that you're basically bypassing the thermostat.
So in my case, the compressor turned on and the fan turned on so we know that both of them do work. If you see that your plunger is pulled in yet nothing is working then chances are your capacitor is bad.
Another thing is generally when you press that plunger in you should hear something even if the capacitor is fully dead you should hear it humming or trying to start.
If you hear nothing at all then chances are that you do not have a 240 volts supply coming in. So do check your disconnect switch and see if there's a breaker tripping.
Reason No #7: Your AC Capacitor Has Gone Bad
You also need to check your capacitor. Because with time most of the capacitors die so make sure to check those capacitors from time to time. All you have to do is remove the capacitor and check it with a multimeter. I have a full guide on how you can check and replace your capacitor.
Check Out the Full tutorial on How to check and replace your AC Capacitor
Reason No #8: You Have Broken Wires At The Condenser Unit
Sometimes if you get unlucky you'll find a mouse nest in your condenser unit. So what they do is they chew up your wires and that causes tripping. If you have a mouse nest inside your condenser unit then investigate all the wires properly. If you have broken wires then replace them with new ones and you’ll be good to go.
Reason No #9: Your Have A Dirty Condenser Unit
So condenser unit does a lot of heat pumping throughout the years. And generally, it also sucks all the dirt and debris from the surroundings. So it gets dirty and plugged up over time. You need to clean the condenser unit at regular intervals so you don’t have to face any problems.
Reason No #10: Your Condenser Fan Motor Has Gone Bad
So the next thing you need to check is the condenser fan motor. What you can do is take a long stick or a screwdriver stick it in the fan blade and give your fan a push. It should spin relatively freely if yours is stuck or seized up. Then you may need to get a new condenser fan motor or you can try oiling it up and hopefully, that'll last you a long time.
Note: After doing all these DIY things if your ac is not turning on then you need to call a technician. Because other ac components are complicated and require skilled professionals to operate.
