Air compressor issue.

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  • #40266
    disco2
    Participant

    Hi it’s Will I know this is not really the place for such equipment but I thought someone may have experience of air compressors and might be able to help. I have a belt driven air compressor it’s electric powered. The issue is that it turns over a few times but then just hums until the overload cuts out. It will work if the tank is empty or if I undo the union on the air pump to tank. I am thinking it’s probably the motor start capacitor. I don’t think it’s the check valve on the tank because I can undo the pipe from the pump to the tank without the air escaping from the tank. I was going to replace the capacitor but it’s proving to be difficult to find one so I though I would ask in case I’m missing something.
    Thanks for your help and advice
    Best wishes William

    #40267
    charlie
    Keymaster

    I have a Machine Mart compressor with exactly the same fault and just put up with having to undo pipe.

    #40268
    disco2
    Participant

    Hi Charlie the trouble is with my one it won’t restart once the tank loses pressure. When I get it sorted I will let you know what I did.
    Best wishes William

    #40269
    aquila787
    Participant

    I had same problem years ago. There was a pressure relief valve in a special fitting which relieved the tank pressure from the cylinder. When I opened it up the little stopper was covered in gunk. Cleaned it up and gave the supporting spring a slight stretch and it ran fine again.

    There’s also a little valve over the piston that moves up and down with air movement (usually made of thin stainless steel…it could be gunked up too.

    #40279
    disco2
    Participant

    Hi it’s Will thanks for that I will have a look do you know if there was pressure in the line between the head and the tank when your valve was gunged up. There isn’t when I checked mine but I’m wondering if there is an unloader that should stay open untill the motor is up to speed before it starts fill the tank. When I push the switch to the off position I do the the usual hiss of air presumably that’s releasing the air between the head and tank.
    Thanks for your help and advice
    Best wishes William

    #40280
    aquila787
    Participant

    There was air in mine till I fixed the spring valve. That was why it wouldn’t start.

    If you’re trying that, don’t try with air in the tank as things could go flying fast.

    If there’s no pressure there then it could be your capacitor. Check the microwaved rating on it and have a search on ebay. Usually plenty of them there.

    #40281
    aquila787
    Participant

    That should be microfarad rating.

    µF

    • This reply was modified 1 year, 7 months ago by aquila787.
    #40366
    disco2
    Participant

    Hi it’s Will just a quick update I fitted a new motor Start capacitor and it’s solved the problem. The compressor starts now even when there is pressure in the tank so fingers crossed it is fixed. I would just like to add that if anyone is planning on removing a capacitor take care the capacitor holds a fair whack of electricity if it’s working so be careful when trying to remove they hold power even if it’s unplugged.
    Thanks for your help and advice
    Best wishes William

    #40367
    wristpin
    Participant

    The correct procedure is to discharge the capacitor before working on the machine. Googling produces a variety of answers , but perhaps a qualified person will provide a definitive answer.

    #40368
    charlie
    Keymaster

    Best practice when dealing with charged capacitors is to let the apprentice do it.

    #40372
    trusty220
    Keymaster

    In my experience they usually have bigger hammers!

    #40378
    hdtrust
    Participant

    Yes I had the same problem on the air compressor for the brakes on a brand new Bedford TL coming out of Windsor SALTEX one year. The problem was solved by sprayed new paint which had got into the non return valve, so releasing the air pressure. Unfortunately to get to the answer was extremely expensive, as the lorry fully loaded with exhibits from The Hall & Duck Trust, did not stop at a roundabout writing off 3 brand new cars! At a test track the following day the Police took the lorry through its paces and wrote off a brand new squad car, yes the lorry failed to stop! It was only when they stripped the compressor in the Police workshops that they found the problem. Due to the way we packed the lorry we had no breakages! The insurance bill at the time was astronomical, which the hire company for the lorry had to pick up. My license was fortunately clean, the best news of all no one was seriously injured.
    The moral of this story is never trust anything brand new!

    #40381
    davidbliss
    Participant

    I have an old think pre war Citrigan welder, it has a large Capacitor, 1’ftX 6”inches 18”inch deep, I had turned the power off to work on a strip light, looking down from top of ladder could see my extension lead light still on, funny all power was turned off, welder was plugged in but not on, just a thought pulled the welder plug out and off went the lead light. so just bridged across the welders plug and quite a crack and spark, don’t think it would have done me much harm but up a ladder the fall might have been worse, had the welder looked at and the capacitor was wired in wrong side of switch and when switched off the capacitor wasn’t being discharged through the transformer, was told definitely not to touch the capacitor, what do you think the large two inch high porcelain insulators are for.

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