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Problem: How do I wire up a dual round capacitor?

troubleshooting air conditioners and heat pumps

Problem: I forgot how to wire up the dual round capacitor that I purchased from you. How do I go about wiring it up so it doesn’t blow the capacitor up again?

Answer: Thanks for your interest in our web site! You would need to look at the wiring diagram that came with the unit. Usually the wiring diagram is glued to one of the panels on the air conditioner. Hope you can read it. Round dual capacitors on the top should be marked: Herm, Com and Fan. Rule of thumb on wiring the capacitor is: Herm on capacitor goes to the start winding on the compressor, Fan on capacitor goes to brown fan wire that goes to the fan, and Com on the capacitor comes off one leg of the contactor to provide power to the capacitor. There are usually more than one wire connected to the Com terminal. The Com terminal is used so other components like the fan motor of the air conditioner can steal power off the Com connection. Below we have two YouTube Videos that explain how to troubleshoot Air conditioner and heat pump capacitors. If you have any questions please email us anytime: God bless you and your family today and always. Sincerely, Steve Arnold

32 thoughts on “Problem: How do I wire up a dual round capacitor?

  1. Hello Steve, I ordered a run capacitor for my AC compressor to have as a backup. The new unit has an orange CPT terminal which my unit does not have. Did they send the wrong unit or Is it ok to use without the CPT terminal?

    1. Hi Jesse! I am very sorry, but I do not know anything about a CPT terminal and have never installed a capacitor that has this feature. I am sorry that I can not advise you on this. This is what I found when I researched the topic:,Easy%2DStart%20%E2%80%9C5%E2%80%9D I hope this helps you out. Steve

      1. Thank you for your assistance.

      2. You are welcome. Thank you so much for your question and kind words! Steve

  2. Hi, I have a question about my dual-capacitor. It’s for a goodman 18 seer, DSZC180361: had it about 6 years. Anyway, today it stops working (clicks, fan starts to whirl, then stops, no compressor going). I check codes flashing which suggest faulty capacitor wiring. I see that the capacitor has no wire going to fan terminal. Yellow to Herm; red to Com, and two other black wires to Com. Nothing to Fan. Is this my problem? If so, why did it take 6 years to appear, when miswired this long? Will other parts have been damaged from this miswiring?
    Any suggestions welcome

    1. Hi! I looked up the parts for your heat pump and some of the heat pump models with your model number had ECM motors. ECM motors do not have a capacitor that I know of. If your unit does not have a fan capacitor then more than likely you have an ECM motor. I will send you a parts PDF to your email address. There were 4 different units with two letters at the end of the model number either AA, AB, AC, AD or AE. If you have an ECM motor most of the time the motor module goes out. If you can find the part number for the motor module that is less expensive than replacing the whole motor. I am sorry, we do not stock any ECM motors or motor modules because they are so expensive. It would probably be best to call in a tech who can diagnose ECM motors if you do have an ECM motor. Sorry that I can not be much help.

  3. Hi Steve.. I have an “out of the box” question. I have an old 1.5HP 110v ac motor on my compressor that has a start capacitor on it. I would like to add a run capacitor to it to give the motor more life while it runs for the short time to fill up my tank. I was thinking about using a run/start cap where it will replace my start cap and add a run cap side as a dual purpose. Does a dual run/start cap work this way? If it does, which side “fan” or “Herm” is the start side and run side and what is a good size for a run cap for this 1.5hp 110v ac compressor motor. And If it can’t be used this way, I want to simply add a run cap to the motor side of the contactor and I need to know a good size here too. I know it’s not made like this but I want to make this happen. Will you please help with any answers you can give me for my questions? I hope I was clear enough. Thanks Robert

    1. Hi Robert! As far as I know, I am not a motor expert, this what you are asking to do is not possible because you would need PSC (Permanent Split Capacitor) motor and more than likely your compressor motor is a shaded pole motor or another type of electric motor that will not allow a run capacitor. In other words, the motor windings and motor would have to be made at the factory to accept a run capacitor. Here is a good video that explains the different types of blower motors. I would like to suggest that you either call a motor shop, a place where they rebuild electric motors and ask them your question or take the motor to an electric motor rebuild shop and ask them if a motor run capacitor can be installed on your motor so it will run more efficiently. I am sorry that I am not knowledgable in answering your question. Please let us know if you find an answer to your question. Steve

  4. Hi Steve. Thanks a lot for your help on the pdf I got from you. I tried to wire my single run capacitor as instructed in the pdf file. But still face another challenge, out door unit is not getting power, but indoor unit gets power. Can this problem be related to poor capacitor wiring? or its just another case.?

    Wishing you the best of lucky,

    1. Hi Isaac! The capacitor wiring would not have anything to do with the unit not getting power unless the capacitor was wired in a way that would throw the circuit breaker because of a direct short to ground. I would like to suggest that you get a voltmeter, set the voltmeter to “Volts AC” and test between L1 and L2 on the contactor. You should have between 220 to 245 volts between L1 and L2. This would be the power coming in from your disconnect box to power your outdoor AC unit. If you are not getting 220 to 240 volts to the unit then you have a high voltage problem. This could be caused by a breaker that needs resetting, a bad breaker or loose or burnt wires. If you are not familiar with electricity then I would like to suggest that you can either an HVAC tech or an electrician in to do the troubleshooting. Dealing with electricity can be dangerous. If the contacts on your contactor are not pulled down and making contact when your thermostat is calling for cooling then you have a low voltage problem that could be caused by a thermostat problem, thermostat wire problem, low voltage transformer problem or a low or high-pressure safety switch problem. Your unit could be low on charge and the low-pressure switch might not be allowing your unit to come on. We have an air conditioner troubleshooting flow chart that I hope will help you determine where the problem is: We have lots of air conditioning and heat pump troubleshooting questions with answers and Youtube videos on the following page: We also have an air conditioning and heat pump troubleshooting simplified page that I hope will help you find and fix the problem: We also have lots of troubleshooting advice on the following page: If you have any specific questions please let me know. I hope you have a great day! Steve

  5. I have an Intertherm CNS30B central air conditioner for my mobile home. Stopped working, read about capacitors and saw that my compacitor was totally rusted, so bought a replacement. So far, so good. BUT it appears I only have two wires to connect! One clearly leads to the fan, the other appears to lead to the compressor. There does not appear to be a wire to attach to the “C” terminal? Huh? When connected, fan starts handily (didn’t before) but there is no actual cooling. Turn off immediately, reach down and feel the compressor, its warm, so thinking that it is trying to work, but not getting enough juice? I keep looking for another wire to attach, but there doesn’t appear to be one. Got a clue for the clueless

    1. Hi Lee! There has to be a power wire that usually comes off the contactor to power the capacitor which goes to the C Com terminal on the capacitor. I would like to suggest that you look at your unit’s wiring diagram if you can find it. Every capacitor has to have power input. The two wires that you have should be one, usually, the brown wire that goes to the fan motor and the other wire should go to the start “S” winding of your compressor. Sounds like you need to add a power wire for the capacitor. I am afraid to advise which side of the contactor to get the power from that is why I would suggest looking at your wiring diagram. I hope you can get it fixed soon! God bless you. Steve

      1. Wring diagram seems like a good idea, since I didn’t notice that small capacitor looking thing off to the side that maybe is for the fan? Like I said, the capacitor I replaced only had two outlets on top, and all the replacements available had three. So, this is mis=wired, which would explain why the fan runs but the compressor is weak? Just hoping I didn’t kill it.

        But Interhherm is as helpful as….well, they aren’t. Tells me my unit is too old for me to get info! Like they don’t keep stuff like that. Any idea where I can get one?

      2. I am sorry, Lee but I do not have an Interhherm parts program or distributor who I can call for wiring diagrams and parts. You might try to call Repair Clinic or go to their site: Sorry that I can not help you out. Steve

  6. Hi, I damaged one of my wire ends taking it off the capacitor. Where would I buy a replacement wire for my GE brand 97F9848 5uf 40uf 370 volt air conditioner capacitor? I have ordered a replacement capacitor from Amazon, but I didn’t see where to order any wires. Please, can you help?
    Thank you

    1. Hi Randall! I would suggest that you go to your local Home Depot or Hardware Store to purchase wire. You will probably need to purchase a solderless crimp connector to install the wire connector on to the new wire. Home Depot has solderless wire connectors and wire crimping tools too. I hope you can get this taken care of. Happy 4th of July! Steve

  7. hey ,
    would you help me with a 5 wire fan , compressor and 3 pole capacitor circuit diagram

    1. Hi Rocky! I will be glad to try and help. If you want to send me pictures you can to our email address: or there is lots of information and youtubes on the following AC Service Tech site: I hope this helps you out. Happy 4th of July! Steve

  8. I have a RHEEM AC unit which I replaced the capacitor about 6 months ago. It’s what I believe to be a dual round cap. Recently, the fan runs, but sounds like it tries to start the compressor and then gives up – tries several times and then the fan quietly stops and the cap continues to just buzz. I bought another cap, but this cap only has 1 pole on the FAN terminal so I can’t replace the old one. My old cap had 2 orange wires connected to 2 poles on the FAN terminal. One wire went from FAN to contactor and the other to the FAN motor I believe? Why is there a jumper from FAN to the contactor? I see this is the same with my smaller AC unit next to this larger one (smaller is bedroom and larger is rest of house). In all of my research I typically see 3 wires to the cap. Why is mine so different?

    1. Hi Jason! I really do not know if I can answer your question since I can not see what you are referring to. It sounds like you had a dual capacitor before that controls both the condenser fan and the compressor. That is why they are called, “dual capacitors” because they are run capacitors for both the fan and compressor. On the dual capacitor, you would have one wire that would come from the contactor, the power wire and attach to the “C” common connection on the dual capacitor. The Fan connection on the capacitor would go to usually the brown wire of the fan motor and the Herm connection on the capacitor would go to the compressor’s “S” start winding. When you have single capacitors, two capacitors, one for the fan and one for the compressor you would need a power wire going to both capacitors. So one of the capacitor terminal sides would have a power wire and the other side of the capacitor would go to the brown fan wire and on the other compressor capacitor, the other side would go to the start winding. I have never seen where there are two wires connected to the fan terminal of the capacitor. I have seen multiple wires connected to the C common of the capacitor, but not the fan terminal. I would like to suggest that you look at the wiring diagram that came with your AC unit to try and figure out the wiring. There are lots of Youtube videos on the AC Service Tech site: I hope this will help you out. I would love to be a pilot. How awesome it would be able to fly a plane! You have to be highly intelligent to be a pilot! I am sure you can fix your air conditioner. God bless you. Happy 4th of July! Steve

  9. I got a dual capacitor 80/5 370v where they used two brown wires for both the hememic and fan wire.
    the common is red. during the swap, I totally forgot to label it and now I am confused which is for the hememic and which one is for the fan.
    how do I figure out?



    1. Hi Derek! You would need to trace your two brown wires to see where they terminate. The one brown wire that terminates and it attached to your fan would connect to the “Fan” terminal on your capacitor and the wire that terminates or goes to the compressor S (start) winding would attach to the “Herm” on your capacitor. If you have any more questions please let me know. I hope you have a great day and weekend! Steve

  10. I have a motor that come out of 12000 btu window air conditioner im using it as a shop fan but i got to hand turn it to start it .i want to wire a capacitor to it .the power to the motor wire is black and white and ground. I have a dual capacitor dat come out same air conditioner. I need to know if and how to hook capacitor to the black and white wire on plug.

    1. Hi Al! I am sorry, but I do not know how to wire up the capacitor on your window air conditioner’s motor. You might not have a split capacitor motor in your air conditioner, but since you say that you have a dual capacitor in your air conditioner, I would think that the motor is a split capacitor motor but I do not know how to advise you to hook it up without looking at the wiring diagram that usually is attached to your air conditioner somewhere. I would like to suggest that you use the wiring diagram to wire up the motor if you can find the wiring diagram. I am sorry that I can not give you any advice on this. Steve

  11. My AC Capacitor has two wires, one to the Compressor, and the other to the common terminal. No wire to the Fan terminal, is this correct?

    1. This would be correct only if your condenser fan motor does not use a capacitor or if someone install a separate individual capacitor for the fan motor. They could have the dual capacitor wired to only power the compressor. I have seen this before when a new fan motor is installed or if the contractor does not have the correct capacitor for both the fan motor and compressor on the truck. Thanks for asking this question. Steve

      1. Thank You for sharing your knowledge.

      2. Thank you so very much for your kind words! Hope these posts will help people troubleshoot and fix their heating and air conditioners.

  12. Terminal connection

    1. I really do not know what your question is exactly. The terminal connections on top of the capacitor should be marked: Herm, Com and Fan. If you have any other questions please let me know. Steve

      1. Hi Steve, I have a capacitor with only two terminals which not labeled, each terminal has four pins. So, How would I know either the herm or Start terminal?

      2. Hi Isaac! Sounds like you do not have a dual run capacitor, but you have a single run capacitor. A dual capacitor has 3 main groups of terminal connections and they are labeled: Herm, Com, and Fan. The capacitor is called a dual capacitor because it is connected to both the condenser fan motor and hermetically sealed compressor. On a single capacitor like you have, it would only control one part. It would only control the fan motor or the compressor. That is why the two groups of four terminals are not marked with any markings like the dual capacitor. We have a pdf file on the following page where I draw a diagram on how to wire a single capacitor in place of a dual capacitor: I hope that this helps you out. I hope you have a great and blessed day! Steve

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