We all talk about capacitors but....

Discussion in 'Non-audio related DIY' started by Champco, Jun 16, 2018.

  1. Champco

    Champco Super Member

    Messages:
    1,437
    Location:
    Twin cities
    When you need one you need one. All last week i was reading on cap to do a recap on my amp not listening to my inner voice telling me something. The most experience I have with Capacitors is in motors. Capacitor start motors. Last night my A/C failed to cool.
    So having a background in A/C I start looking into it. In the past I have had to fix freon leaks and it has been fine for a number of years. Well I assumed it was leaking again. So I put the shoes on and I was going outside to feel the supply line to see how cold it was and realized the compressor was running and the fan was not.
    It was getting very hot so I pulled the fuse block. I take off the panel and notice the contactor is cracked and a copper buss was dangling on one side. played with it and was unable to get it to start. Looking at the capacitor the top was no longer flat but it was swollen in such a way it symmetrical looking and i ignored it.
    This morning I run to the local supply and purchase a new contactor, put it in and duh, It was not starting. So I pull the cap and look closer to the bottom was swollen. The parts place has closed. I did have a spare but gave it to my son a time ago. Long story short i acquired one from a friend in the biz and put it in and everything is cool now. point coming.
    Keep a spare A/C capacitor. It will go bad. Mine is commonly used in most condensing units.
    377-440 volts 35-5 Uf Mine was a 35-7.5 uf but this one will work just fine.
    On monday I am buying two. One for me and one to replace the one I got today.

    Stay safe.
    Pull the fuse block near the A/C unit and shut off the furnace power. Most are switched on the side. This is where the 24v control comes from.
     

     

    Please register to disable this ad.

  2. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

    Messages:
    31,442
    Location:
    Central Missouri
    Wife bought a cheap plastic floor fan last year, I hated it because I have old metal cased box fans from the 80s that just go and go with a little oil in the bearings. Anyway it lasted for one season and quit. I said I'd look at the bearings, maybe they seized up. It had a 4 uf run cap that was swollen. Darn thing was almost brand new. I had scrapped out a couple of dehumidifiers with failed compressors and saved some parts. Sure enough I had a 5 uf that I put in, and it cranked right up. I was a hero. Bad news is, I still have to use that stupid plastic fan! :D
     
    Champco likes this.
  3. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    35,874
    Location:
    Southern NJ
    I had an AC unit at work die in a similar manner. It was partly bearings, but I think the cap was also dying. I pumped oil in to make the squalling stop but when the replacement motor arrived 2 days later I found the original was so hot I couldn't even touch it. It spun fine by hand, so I don't think it was a friction problem. It was also hot in the middle of the motor, not at the ends. Thinking the cap was dying and making the motor hot, which may have been why the oil in the bearings cooked out. Either way, I bought a cap with the motor because it was less than 10 bucks. Put both in and it worked like a charm. I didn't even try the original cap, didn't want to risk roasting the new motor.
     
  4. wlhd1610

    wlhd1610 Penny and her new friend Subscriber

    Messages:
    2,343
    Location:
    upstate new york
    Rule of thumb in the business: new motor always gets a new cap.


    Bob
     
    Pio1980 likes this.
  5. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    35,874
    Location:
    Southern NJ
    That was my thinking. I wasn't sure if the cap damaged the motor or if the motor damaged the cap, but either way I did not feel like fooling with it again anytime soon. The original parts lasted more than 10 years, if the replacement ones last another 10 the unit will probably be due for replacement at that point. Honestly I find that I do not like repeat work. Fix it once and be done with it. Probably why I can't make a living at fixing stuff.
     
  6. Pio1980

    Pio1980 AK Member Subscriber

    Messages:
    25,141
    Location:
    Angel Station, Alabama
    I replaced the twin cap in the outdoor unit but they buried the one in the indoor HVAC and I cannot get to it to replace it without major surgery. I have to manually start the fan after power interruptions until I figure out which motor wires go to the cap and gerry rig it in.
     

     

    Please register to disable this ad.

  7. Wildcat

    Wildcat Audio Sommelier

    Messages:
    4,546
    Location:
    MI, US
    Good deal keeping a spare capacitor on hand. A few years back, the AC died here overnight. Woke up stuffy in the house. When I went outside, I heard the unit hum for a bit, then kick off. Then after a spell it would hum again, then kick off. The blower fan in the condenser coil was also very hot. Yep, it was the capacitor. I replaced it, and it ran fine all summer. Next summer, it's spring and the AC won't start up again. Sure enough, the capacitor was dead again. Replaced it a second time, and it has been running since (about three years now). Learned from an HVAC pro that these newer chinese capacitors are absolute junk, and will fail at any given moment. The first one I replaced was likely the original. The second one didn't even last a whole year. This one is a dual capacitor (one for the compressor, one for the fan), but luckily they are common enough that they are easy to find, even on Amazon and eBay.

    Another common repair I've found: the fan goes bad on the compressor unit. The lines ice up inside (as do the evaporator coils), and airflow is restricted. Problem--the fan outside is worn and does not spin at the proper speed. I have seen that twice--my dad's old AC unit did this, and the same happened in one of my prior houses. Both times, new fans got the system back up and running properly.
     
  8. Dr Tinear

    Dr Tinear AK Subscriber Subscriber

    Messages:
    5,152
    Location:
    Livonia, Michigan
    I've had two of those run caps go bad over the years. The first one was on the A/C compressor's condenser fan motor. I had just purchased a new digital multimeter that measures capacitance, so when everything else in the motor circuit looked okay, I disconnected the cap and measured it. The meter said that its value was about 99% below what it was supposed to be. I bought a new cap, put it in, and the A/C worked again. The meter paid for itself that day by saving me the price of a service call.

    The second failure was the furnace blower motor run cap. The motor would only run slowly and the motor case was hot. This time I recognized the symptoms, measured the cap to confirm my suspicions, and bought and installed a new one. Problem solved.
     

Share This Page