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Comfort Specialist
Comfort Specialist, HVAC Technician
Category: HVAC
Satisfied Customers: 1368
Experience:  Master Lic. holder for HVAC & Gas, Contractor, Estimator, Designer, Air Balance Certified, LG Master Commissioner, UNC Cert. holder for Industrial Ventilation
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Capacitor for air conditioner unit not working.

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My Goodman CKL36-1 Air Conditioning Unit has stopped working. It won't even turn on. I have attempted to change the fuses, but that has not helped. What do you think the problem is?

Can you tell me is anything operating? Does the blower run when you switch the thermostat fan switch to ON? Also, when you say changed fuses, where did you change the fuses?

Customer: No, the blower does not work when I turn it on. Nothing is operating.

Wvfan79:

What fuses did you change?

Customer:

The fuses on the outside of the house. The fuses were to the unit, the time delay fuses.

Wvfan79:

Ok, do you have a battery powered thermostat?

Customer:

I don’t know. How would I check?

Wvfan79:

See if the cover pulls off the thermostat or if the entire thermostat pulls off the base. You can try rolling it up or down away from the wall.

Customer:

No, it does not pull off the base.

Wvfan79:

May also have a flip down cover or there may be a button that releases a battery compartment. Does the thermostat display work?

Customer:

Yes, there is a battery compartment, when I take it out the display stops working.

Wvfan79:

Okay, so the batteries are good?

Customer:

Is the battery just for the display or the whole thermostat?

Wvfan79:

The whole thermostat but it is also powered by the furnace. Do you know where the furnace is located?

Customer:

Yes

Wvfan79:

Okay, go to the furnace and pull both doors off. On the control board found by the blower assembly there is a 3 amp car-type fuse like this plugged into the board. Pull the fuse and examine it. See if it is blown.

Customer:

We found a plug for the furnace/air conditioner unplugged. We plugged it in and the inside unit works. Now the outside fan works, but when the condenser attempts to turn on, there is a noise but it doesn’t click.

Wvfan79:

Has the unit been worked on lately?

Customer:

No. The outdoor unit is 6 years old.

Wvfan79:

So, the indoor fan is blowing now and the outdoor condenser fan is running but the compressor did not start?

Customer:

Yes.

Wvfan79:

Give it a minute and place your hands on the copper pipes entering the outdoor unit and make sure they are not getting cold or hot. Be 100% sure the compressor is not running. One thing you can do is pull the wall mounted disconnect by the outdoor unit and wait a second and plug it back in, or switch it on depending on what type you have. When you do listed to the compressor and see if it starts or tries to start or if it runs for like 15 seconds then shuts off. Listen carefully. Once you have performed the above steps reply to me. If you hear nothing or can't tell we will then want to pull the service access door off of the unit and inspect the unit's capacitor. If the top cap is swollen like this it is your problem.

Sometime if it is not swollen it can still be bad internally. You would want to power the system down at the disconnect and the panel, then discharge the capacitor by using an insulated screwdriver to bridge the terminals (while only holding the rubber handle), lastly mark the wires then pull them off. Once off take the capacitor to a local HVAC parts supplier for testing as it takes a special tool to test them. You could also replace the capacitor if you feel you'd rather do that. It should only cost 20-40 dollars for a replacement.

When I mentioned pulling the disconnect above, I meant with the thermostat set to cool and with the temp down. The compressor fan should be running when you pull the disconnect.

Customer:

Ok we were about to try the above steps when the outdoor unit turned off. There is a humming noise but it is not turning back on

Wvfan79 :

The humming is the contactor, that’s normal. Go make sure the thermostat is bumped down low.

Customer:

OK the thermostat is low.

Wvfan79 :

Was it low before?

Customer:

Where is the access door? Would it be in the rear of the machine. And yes it was low before.

Wvfan79 :

Rear corner above the copper lines. 2-4 screws to take off. Be careful, the unit contains high voltage. The capacitor is bad it may also be why the fan shut off. While you are in there, see if the contactor is pulled in.

The center plastic tab says pulls in with 24 volts should be depressed inward. You can use an insulated screwdriver or the eraser end of a pencil to depress it. If it’s not already depressed the unit may start when you press it down and hold it. Please keep me filled in on the details of your findings.

Customer:

Ok we see the capacitor and the top is not bulging. We will take it out tomorrow (no shops open now). We are looking at the contractor now and we are attempting to depress the tab now. We hold it down and it comes on but it won’t stay down.

Wvfan79 :

Ok so the unit indoors is not calling for it to run. The furnace sends 24 volts to the thermostat which then sends the voltage to the outdoor unit. Did you put the furnace doors back on?

Customer:

No. We will now.

Wvfan79 :

That's why the contactor isn't pulled in. Once you do that, give the unit about 5 minutes or so to see if the compressor starts. Have someone stand next to the unit and listen for the compressor when you install the doors. Then feel the pipes. Did the contractor pull in?

Customer:

No, we attempted to push it in again but it didn’t stay.

Wvfan79 :

It should pull in on its own. When you pressed it in did the compressor and fan start on the unit.

Customer:

It is depressed now but the compressor did not turn on.

Wvfan79 :

Did it pull in on its own?

Customer:

Yes.

Wvfan79 :

Did you hear the compressor try to start?

Customer:

Yes.

Wvfan79 :

And it shut down when starting? Or did it run for 15 seconds or so?

Customer:

Yes.

Wvfan79 :

You are 100% positive it's not running? You felt the pipes?

Customer:

Yes, we did feel the pipes, it was not cold or hot.

Wvfan79 :

Ok, the capacitor would be #1 check, then after that I would suspect you may have a low refrigerant charge or possibly compressor issues. The likely cause is the capacitor. Be sure you power it down and discharge the capacitor before removing it. Can store an electrical charge.

Customer:

Ok, we will check that tomorrow and have someone check it.

Wvfan79 :

Sounds great!

Customer:

Thanks for the help

Wvfan79 :

You are very welcome. It was a pleasure working with you tonight!

Customer:

You too. Thanks.

Wvfan79 :

Once you test it tomorrow you can always jump back on here and come back to this question.

Customer: Okay, great, thank you.

Comfort Specialist and other HVAC Specialists are ready to help you

Capacitor for air conditioner unit explained 

Capacitors are a small cylinder object that helps store energy. This sends a shock to help start the motor or help keep the motor running. Capacitors work hand in hand with compressors, blower motors, and outside fans found in the air conditioner. 

Checking an air conditioner capacitor 

Use a voltmeter to check if the air conditioner capacitor is running properly. Using a voltmeter helps determine if there is a blown capacitor. However, this can be done just by listening to the unit. Listen to hear if there is any humming noises or look to see if the fan is spinning. If the AC is still humming, but the fan is not spinning, this can be an indication there is a capacitor issue. 

Issues with bad capacitors 

Capacitors withstand damage from power and can also wear down to where they will not hold a charge. When a capacitor begins to fail, normally individuals will begin to hear a clicking noise. However, if the motor completely stops working, a ac repairman will need to be called. 

When a capacitor stops running, the motor will still try to kick on, but instead it will make a humming noise. If the humming continues, the motor can burn out and will need to be completely replaced. 

Capacitors that become weak and are connected to the compressor can go into what is called “hard starting.” This is when the ac will try to turn on, but then shut back off. This causes a lot of pressure on the compressor and other parts within the ac unit and eventually the system will need professional attention. 

In many cases, AC professionals will replace the capacitor that is causing the issue. Individuals who do not have proper knowledge on how to replace an ac capacitor should not work on them alone. Since oil can leak from broken or damaged capacitors, this can become a dangerous job.

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