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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8139
Experience:  Furnace, A/C and heat pump specialist.
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Need help wiring my ac capacitor

Customer Question

Need help wiring my ac capacitor
Submitted: 10 months ago.
Category: HVAC
Expert:  airheatman replied 10 months ago.

What is the model on the ac unit?

Customer: replied 10 months ago.
Mc36-6g
Expert:  airheatman replied 10 months ago.

Is his a central ac unit?Not seeing this as a good model. Is there a diagram on the unit?

Customer: replied 10 months ago.
It's a roughly 40yr old unit. The fan motor went out. Replaced it with a like unit. I can get the fan to work, but every time I connect the compressor, it trips the breaker. And yes, central ac.
Customer: replied 10 months ago.
there is a diagram on the panel.
Expert:  airheatman replied 10 months ago.

1. Is that number off of the outdoor unit?

Can you attach a pic of that diagram?

Usually we will have 3 terminals on capacitor.

Fan, COM and HERM

Customer: replied 10 months ago.
That's the original capicitor. The new one is the same on top. No writing. And yes, that's the number off the panel. A guy I spoke to added a o, or a 0 before the 6 and found it somehow.
Expert:  airheatman replied 10 months ago.

Compressor has 3 wires. One to T1 on contactor, one to T2 on contactor and the other to HERM on Capacitor

Fan has 3 wires. One to T1 on contactor , one to T2 on contactor and one to FAN on capacitor

Then there is a wire from T2 on contactor to COM on capacitor.

Often the wire from compressor or fan will go to the COM on capacitor instead of directly to T2 as COM is fed from T2 on capacitor.

Expert:  airheatman replied 10 months ago.

Give ,me a minute to look at those images

Expert:  airheatman replied 10 months ago.

Let me draw this for you

Customer: replied 10 months ago.
The new fan motor has five wires. One to ground, two to contactor, and two brown ones that connect to the new capicitor, I was told. Here is the new capacitor.
Customer: replied 10 months ago.
There's no identification on either capacitors.
Expert:  airheatman replied 10 months ago.

OK so fan you have figured out yes?

Customer: replied 10 months ago.
I believe so. It spins.
Expert:  airheatman replied 10 months ago.

OK I am drawing the diagram for the large compressor cap

Customer: replied 10 months ago.
Ok
Expert:  airheatman replied 10 months ago.

OK here is what you will do.

1.You have 2 power wires coming into the unit.One will go to L1 and the other will go to L2 on the contactor

2.You will have a wire coming off of T1 on contactor going directly to C on compressor

3.You will have a wire coming from T2 on contactor and going to R on compressor and one side of the compressor capacitor

4. You will have a wire from other side of compressor capacitor going to S on compressor.

See the drawing I made

Customer: replied 10 months ago.
Does it matter which side on the capicitor?
Expert:  airheatman replied 10 months ago.

NO makes no difference on a single cap

Customer: replied 10 months ago.
I have it hooked up right. It still throws the breaker once I supply power. Only after I hook up the compressor. And I believe it's only after I hook the two wires to the contactor.
Expert:  airheatman replied 10 months ago.

Sounds like a bad compressor. Do you have a multimeter for troubleshooting?

Customer: replied 10 months ago.
I do.
Expert:  airheatman replied 10 months ago.

Excellent. Turn power off. remove wires from compressor terminals. Set meter to read continuity. Put one lead on a known ground such as clean refrigerant copper line or a ground screw. Then touch other meter lead to each terminal on compressor and see if we get a reading from any terminal to ground.

Customer: replied 10 months ago.
Unless I'm doing it wrong, I'm getting nothing
Expert:  airheatman replied 10 months ago.

OK that is GOOD. We don't want any reading there. Next put one lead on each of the terminals . (R to C, C tor S and S to R)See if we get a continuity reading there between terminals

Customer: replied 10 months ago.
Ok, still nothing. Meter says less than 20 ohms.
Expert:  airheatman replied 10 months ago.

OK we should get a reading between each of those.It will not be very many ohms.Are you saying we have ohms but below 20?

Expert:  airheatman replied 10 months ago.

Watch this video starting at about 2:35

https://www.youtube.com/watch?v=6IiIIMcAVGE

Expert:  airheatman replied 10 months ago.

Then watch this one on ohming to ground .Let me know results of both of those tests

https://www.youtube.com/watch?v=hZQ6tr72I0I

Customer: replied 10 months ago.
Either i got really numbers or my meter is bad. The highest i got was 2.
Expert:  airheatman replied 10 months ago.

OK that is fine. But please verify for me you did get some reading between each and every compressor terminal but nothing from any terminal to ground?

Customer: replied 10 months ago.
I did get a reading from each terminal wire.
Expert:  airheatman replied 10 months ago.

Excellent and we should. This means either the compressor is mechanically seized or the capacitor is bad.Does your meter read microfarads? If not you can take the cap to a supply house to have it checked.

Expert:  airheatman replied 10 months ago.

Leaving office for the evening.Nowhere to get cap tested or replaced tonight anyway so I will check in with you tomorrow morning.