The air conditioner and thermostat are always interconnected: when one is on, you may expect the other to be on as well. This is why it can be somewhat surprising to see your air conditioning system still working even if the thermostat is shut off.
There may be a couple of reasons for that, such as bad wiring, malfunctioning electrical components, or a defective thermostat.
However, occasionally, the problem lies in a stuck compressor contactor. With that in mind, you might need to get a new contactor to replace the old one. Read on to find out how to fix a stuck compressor contactor.
What Is a Compressor Contactor and How Does It Work?
The contactor is a switch that you can find in your air conditioner to deliver a voltage line to the unit. In some cases, the same contactor supplies power to both the condenser fan motor and the compressor; it all depends on the AC unit you are using.
When the control power gets to the contactor holding coil, all the contacts should pull in – causing the unit to run.
It’s an essential part of every air conditioning system, and without a functioning contactor, things would not be able to pull smoothly.
You can think about the contactor as a bridge that goes over a river; unless that bridge is down, the cars (i.e., the power) won’t be able to pass from one side to the other. No contact is made.
Therefore, the contactor controls the flow of electricity going in and out of your air conditioner.
When your Air Conditioner unit is not cooling the room, the contactor will go into its “up” position. This means that no power would be going through any of the components of your air conditioning system.
However, once your air conditioner begins a cooling cycle, the contactor will receive a small voltage that signals it should go into “down.” This will allow for the electricity to flow through your electrical components, allowing your AC to operate.
The contactor will stay down until the thermostat is content with the temperature and decides to end the cooling cycle.
At this point, one more dose of voltage will be sent to the contactors, telling them that the energy is no longer needed – cutting it off.
What Causes the Contactor to Get Stuck?
To put it simply, if you have an external unit that is working correctly, then you have a 24-volt current going through the contactor that sets your air conditioner into “cool” mode.
This current causes the contactors to close, powering both the condenser fan motor and the compressor.
Once you turn the thermostat off, there will no longer be any voltage to power the contactors – in which case, both the condenser and compressor are shut down.
Even with that in mind, once the contactor is closed, there will be a curved trajectory (arcing) or electricity. This heat level is average, and often, it could lead to no issues.
At the same time, the contactors (there are usually two) could start heating enough to stick together.
This will prevent the contactors from performing in the way that they should, welding themselves shut in a closed position. This will interrupt the power, but it can also cause the condenser to keep operating – even though, technically speaking, the thermostat is off.
You must remember that the contactors are electrical components. As a result, they will wear with time, and you will have to get new contacts for your HVAC system.
A burn-out contactor will cause the motor to heat and stop running, giving you a bigger cooling problem.
You can imagine that it won’t be “cool” to lose a fan, so you may want to check as often as you can the wires to make sure your air conditioning unit is running smoothly.
A contactor from your AC device can easily remain in one position – and the cause for that is often a buildup of dirt around the contactor. This will keep it stuck in its current position – often, the “open” one.
At that point, a lot of electricity will continuously go through your air conditioning system.
The high power may prevent at least a fan of your HVAC from being shut off – in which case, you might either want to clean or replace the contactor. Mostly, it may depend on the damage the contactor took.
At this point, it’s best to ask for a professional; they will have the rights reserved to take care of the unit properly. They will know every coil, every route that the wires should take, and every problem you have.
If your HVAC system has taken some severe damage, then a professional should know how to fix a stuck compressor contactorbe and make it work properly.
How to Fix a Stuck Compressor Contactor Temporarily
Ideally, to fix a problem with your contactor, you may want to hire an HVAC professional. As mentioned, they have the rights reserved for everything HVAC -related issues and should be able to deduce what is wrong with your unit – indoor or outdoor.
That being said, if the contactor is not broken and does not need to be replaced – then you may try to solve the problem temporarily. You may be able to get the contactor working by simply tapping on it.
If the blockage is caused by dirt, then you can try to manage the issue yourself. However, if the problem is in the coil, the wires, or in any other electrical part of the HVAC system, then you might want to seek the help of a technician. The sooner you call them, the better.
How to Test an AC Contactor
A bad contactor may have a variety of symptoms such as humming, chattering, or even melting. Often, this happens because the coil is weak or because wires release too much heat – in which case, you should consider hiring a HVAC technician.
A professional service will know how to fix a stuck compressor contactor and make the problem go away. They would have the information already stored, so whether you have an indoor or outdoor unit, they should know where to check.
However, if you want to check it out yourself, here is what you should do:
- Turn off the Power. Go to the thermostat and the breaker, and shut down the AC. You should make sure the risk of electrocution is removed as you are working.
- Unscrew Side Cover: Go to the condenser unit and use a screwdriver to open the side cover. You should be able to see the contactor and every corresponding wire at that point.
- Take a Picture: When you load the wires back up, you need to have a visual representation. This way, you won’t be messing up the circuit.
- Remove the Wires and Contactor: Take the screwdriver and remove the contactor. If it looks damaged, prepare a new contactor. Remove the wires as well.
- Test: Take a multimeter and turn it on the OL setting. Connect it to both sides for contacts. If you see a voltage between 5 and 20, then everything should work correctly. However, if the voltage is low or inexistent, you should call a technician and inquire about replacing it.
- Replace the Contactor: If the contactor is the problem, you may want to replace it as soon as possible. Look at some services that can offer quick repairs, particularly if you are going through the warm season.
If the voltage looks good, you should carefully put the wires back together, close the unit and run it.
How Much Does It Cost to Replace a Contactor?
If you have to replace the contactor, after all, you should know that the rates can start at about $125 and stop at $275. It all depends on the price for the part along with local prices.
Emergency repairs can also cost more, particularly if your technician does not have a 24/7 service. If you don’t need a professional service and you have enough experience to change it yourself, then you’ll pay $10-$20 just for the piece.
When you are dealing with a stuck compressor contactor, the chances are that you might have to replace it. The issue might be caused by defective wiring or thermostat.
So, maintenance is often the only thing needed to keep things under control. Hope you found some helpful information on how to fix a stuck compressor contactor. If you have any queries, please leave us a comment, and we’ll try to get back to you as soon as possible.
Jesse Pinkman is a passionate HVAC professional writer who grew up repairing any home appliance on which he could lay his hands. He is responsible for ensuring that every article we publish is SPOT ON. When he’s not in the office, he enjoys hiking, watching football, and spending time with his family.