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Thread: Electric motor question

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    Default Electric motor question

    Can a faulty relay cause an electric motor to oscillate when climate is cold
    Reason, have an electrical appliance that first thing in the morning when cold, ie today in Melbourne is jacket wear. The appliance tries to start but keeps going on and off
    When warm this does not occur
    Any one want to theories so i can start to resolve the problem
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    we might need a wee bit more info to get some teeth into ????? the motor wont be oscillating just going on and off against a load ie gummed up bearing etc whats the appliance ?????

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    Uncle Fester (28-04-19)

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    Sounds more like a dodgy capacitor to me but as said, some details would be helpful like what the appliance is to start with.
    There are a bunch of different electric motors, some have caps some don't and some have start switches which kick in a different set of windings to spin the motor up on high torque before switching to the run windings.

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    Thanks guys, a Brivis Wombat gas heater. I can verify that it is not sensor, control panel nor the pilot light as either changed or had them checked out. It simply starts, stops starts etc first thing in the morning, afternoon no problems??
    ps have even changed the controller, had 2 service men attend but they have no idea, each saying they have checked it out but can't answer why it wont run contiuously
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    your unit has multiple temp sensors , if the air is too cold on start up it will go down in speed until the temp comes up so there is no cold draught blown into the system , check that the fan is not sticking ? then that its starting temp is what its set at . and establish some positive data , like air temp at morning start , air temp at arfo start length of start time as well cheers don

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    Inspired with the information given, climb into the attic, removed cylindrical fan cover, the boss fired up the unit and it went, (thinking it may be restricted air flow inlet??? ) BUT it started to go into intermittent vibration and back to normal. So have now removed the motor, fan and capacitor as one unit and will take to the rewinder tomorrow and get him to test it. Not saying it is the cause but I had put a new cylindrical fan in and had let it run out of balance before rectifying the problem a while back
    Will keep you informed
    Thanks once again guys
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    hinekadon (28-04-19)

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    +1 for Hinekadon's gummed up bearing explanation.

    Soot, grime, whatever is stuck in it tends to be more viscous when cold. I have spun old fans by hand and thought they run free but when it tries to get up to speed, they just don't make it.
    Maybe there is a PTC resistor or polyswitch fuse somewhere that senses the current overload and reduces the current to protect the motor.

    A bit of isopropanol works wonders.
    A ball bearing would need to be re-greased afterwards.
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    OK motor returned from winders, states bearings still good (surprise as i was running it out of balance), states the capacitor good,
    Fan had been slipping, rectified,
    Winder said it did not matter which point i plugged to on the capacitor, started up, spun up then reverted to buzzing noise, reduced revs to a crawl, when i stuck my hand in and tried to spin it up there was resistance from the motor, quickly pulled the power
    Tried to check capacitor with cheap volt meter , 200k Ohms but could not make sense (me) from readings
    Capacitor checked for bulges etc but could not see any. One of the vids said they have a life span about 10 years, this thing has been going 17 years, slight indentation on side which may have happened when removing
    I know stuff all but sounds like capacitor, if i remove this as an option i can move on to hikeadons suggestions re temp meters
    Capacitor number EN60252, can any one suggest a Aussie source who are reasonable

    Just noted another number under the above, CBB65A which brings up more numbers on the internet
    Last edited by allover; 04-05-19 at 04:55 PM.
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    heres the lib/ manual page re setup from the manual , it is possible that its doing what its supposed to do when the air is cold going into the heater .
    your capacitor number is out of wack with reality sounds like a manufacturers part number to me . What is the writing on the cap say ??? looks like 6 micro farad to me they are pretty common any electrical wholesaler will have one they are also used in fluro lite fittings they are not expensive / could have gone open bit hard to tell but a easy fix if it has , Im over seventy and have only see two go intermittant in my career , they usually shit themselves completely but then anything is possible , the motor is only small 3-400 watts so basically any one less than 10uf will do the job , lets know how you get on ????

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