HVAC halp

My blower stopped working the other day. After checking out the usual suspects, I found that the blower would run if I gave the blades a tiny nudge. I figured that the culprit was the capacitor since I read that is a common failure point. Plus the part looked old. Pic related. The rectangular/oval capacitor is the original. The round tall the replacement. Unsure if I have the right part since it doesn't seem to fix the issue. I found out after the fact that there is a diff between a RUN capacitor and a START capacitor, though when looking online they seem to muddle that term and use them almost interchangebly.

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  1. 1 month ago
    Anonymous

    Not sure if I even have it wired correctly since the wires coming out of the blower are both brown. I tested them and they both are giving me +115v vs ground which strikes me as odd. Pretty sure that capacitors are uni directional with one being the input and the other lead the output

    • 1 month ago
      Anonymous

      Many modern power tools have a 3 phase motor and electronics to turn 18v into 3 phase ac.

    • 1 month ago
      Anonymous

      Is it a 240v blower motor? Each hot would be the same referenced to the neutral but should be a higher voltage if measured against each other.

    • 1 month ago
      Anonymous

      >the wires coming out of the blower are both brown
      normally has one brown and one brown with a white stripe

      • 1 month ago
        Anonymous

        frankly the unit is so old that maybe the white just faded or perhaps there was a physical tag that has fallen off. visually they are identical.

  2. 1 month ago
    Anonymous

    Also, because it was mentioned in a video I watched, I don't see any identifying tag on the blower that would provide info. Perhaps it's hidden since I can only see about 1/3 of the blower casing from my point of view.

  3. 1 month ago
    Anonymous

    Could also be a motor winding or something. Dunno what the 40+7.5 means but the original is 7.5 micro farrads, might not be the same but I dunno. You can also test capacitors with an analogue ohm meter but guessing you don't have one of those. I wouldn't worry about the run start stuff as pretty sure that's just different capacitance.

    • 1 month ago
      Anonymous

      Man I really hope its not the blower. It looks like a real PITA to get out. I might have to remove the whole unit just to get room to access it

  4. 1 month ago
    Anonymous

    That's a start/run capacitor that you got as a replacement. Meaning it is both in one package.

    The original looks like it's just a run capacitor, meaning it doesn't have anything to do with starting. Does the thing have a separate start capacitor somewhere?

    • 1 month ago
      Anonymous

      You could make that replacement work, you just don't use whatever terminal that you don't need. Look at the lettering on your original's terminals, and hook the wires up to the matching lettering on the replacement.

      I just wonder if the thing is an older model, it might just use more than one capacitor, instead of using the combo one.

    • 1 month ago
      Anonymous

      a typical blower motor doesn't need a run capacitor.
      op bought a run capacitor which doesn't provide enough amps to start the motor.

      • 1 month ago
        Anonymous

        It was a Sunday. It was cold af and I needed heat. I did what I could. In my defense the original capacitor is not labeled as a start cap. It just has some numbers which I googled and found this part.

  5. 1 month ago
    Anonymous

    The cap you got isn't exactly right, but should work if you hook it up right.
    Referring to my stellar artwork, you can see that your replacement is both the START and RUN caps in a single package. Looking at your pic of the terminals, you can see that one is FAN, one is MERM, and the last one is C.
    I can say for sure that C is Common. You have to figure out which one of the other two is the one you need.
    i.e., since your motor was starting/running with 7uF, you need to figure out which of FAN or MERM is the 7.5uF side. If you have a meter handy, it should be easy to find. If not, find someone nearby with actual testicles to figure itt out for you.
    But idk 100%. I seem to remember reading/hearing somewhere that you can't just not use one half of those dual caps. If it's not too late, I'd consider taking the new one back and get the proper part instead of "close enough."

    • 1 month ago
      Anonymous

      the only reference point is that the old cap has a red mark on one of the ( can clearly be seen in the picture). no idea if this red means it's the common or what. the new cap has no color markings.

      also i felt around the case and i don't feel any other devices or wires coming out

      • 1 month ago
        Anonymous

        > can clearly be seen in the picture

        A capacitor of that type with two terminals cannot be polarized if it is used with AC as yours is. PERIOD. The type that has two caps in one case is not polarized either, but you have to know which is the common and which of the two is RUN and which is START, if they are different. AC caps are not polarized; if you disagree with this you don't understand what AC means.

        • 1 month ago
          Anonymous

          Sorry, my brain was stuck in DC mode. I am clearly no electrician. But I think my question still is relevant, if I know which wire was attached to the red terminal on the old. What do I attach that to on the new one? From google searching, I have surmised that one side is common, one side is 440v and the other 370v

          • 1 month ago
            Anonymous

            I dunno, you sure there ain't any lettering on the top of that old capacitor? There isnt any dirt hiding it? If I had to guess I would say you hook it to the common and fan.

            But i'm obviously no a/c professional, just shoved my dick in a furnace or two and replaced a few capacitors from time to time. I'm smart enough to find an exact replacement, tho.

    • 1 month ago
      Anonymous

      >MERM
      It's HERM - for hermetically sealed
      It's the compressor start cap for an HVAC condenser unit.
      C = Common
      FAN = 7.5 mfd
      HERM = 40 mfd

      connect fan motor leads to C and FAN
      leave HERM not connected to anything.

  6. 1 month ago
    Anonymous

    blower? I hardly know her

    • 1 month ago
      Anonymous

      Thats sad, she gave birth to you

  7. 1 month ago
    Anonymous

    Nevermind, I got it. I just tried different combos with test leads until I got it working. Sorry if I was a bit of pussy about it. When I was young I witnessed a capacitor on a telephone pole go off in a seriously huge explosion. Shit scarred me for life. Even now a days when its a lightning storm I get a little antsy.

    • 1 month ago
      Anonymous

      >capacitor on a telephone pole exploded

      that was a power transformer dummy. its not the same as a capacitor. holy shit you are moronic

  8. 1 month ago
    Anonymous

    I think a start/run capacitor is only used on a/c units btw. It's meant to run both the compressor and fan. I'm guessing you're just replacing a furnace blower cap, which...i dunno, i guess a start/run would work on if you just use the one side, but looks like you'll find out for sure.

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