Motor hums then pops cutout...

[Punx0r]

Hello guys and gals

I've just aquired a little Airmaster tiger (8/25 I think) that doesn't work...

The problem is that when powered on the motor hums loudly, turns a few degrees, stops and pops its cutout switch after about 2 seconds. Spinning the motor by hand doesn't help.

It's free to turn, no smoke or funny smells, no signs of burning/overheating that I can see.

Could this be a problem with the capacitor? I don't know much about induction motors and wanted to check before starting to pull the motor apart

Thanks in advance for any suggestions

Anthony

 

[brightspark]

take a punt and try a new capacitor . u can pick em up of ebay for under a tenner

 

[tigler]

Classic failed cap symptoms !! Maplin stock them, check to see if there's a branch near you.

 

[madkayaker]

sounds llike the capacitor to me! get one as close to the spec as possible and watch the voltage needed as even though its a 230V motor its not uncommon to need a 400V capacitor for the duty cycle

 

[roofman]

just before it pops the thermal hit the fan to turn the motor...if it starts up its the cap gone

 

[Punx0r]

Thanks lads. It was sounding wonderfully straight-forward up until roofman's post

Manually spinning the fan either before or after applying power does nothing to help...

Does this rule out the capacitor? Or is it still worth a shot?

 

[brightspark]

Thanks lads. It was sounding wonderfully straight-forward up until roofman's post

Manually spinning the fan either before or after applying power does nothing to help...

Does this rule out the capacitor? Or is it still worth a shot?

still change the capacitor as spinning the motor doesnt allways work as the capacitor is permanantly conected to the winding

 

[tigler]

Yes, some motors will not self start if the cap is dead.

 

[ilovemygt35r]

ok im going for the brushes just to be different, and maby a damaged/dirty comm if the brushes have worn down too much.

 

[eil]

My vote is the capacitor as well, but take off the inlet filter and slacken off the discharge pipe, a little squirt of air tool oil into the inlet and turn by hand just in case its been standing for quite some time.

 

[brightspark]

ok im going for the brushes just to be different, and maby a damaged/dirty comm if the brushes have worn down too much.

its an induction motor .rotor and stator coils not a brush motor with armature and field coils with carbon brushes

 

[roofman]

make sure your starting it by the propper pull/push switch on the black connection box as this has a pressure loading release on it..these little comps dont like getting switched on by a mains socket against the HISSSSSSSSS valve in the switch box as when 1st switched on they run up under no load from the pump straight to atsmophere then when the motors up to full speed and a couple of psi have been made it diverts into tank

 

[tigler]

ok im going for the brushes just to be different, and maby a damaged/dirty comm if the brushes have worn down too much.

Won't be a brush motor, just a normal induction motor.

 

[leeruddock]

if it is not the capacitor it could be the check valve in the pressure switch.

 

[Punx0r]

Many thanks to all I bought a capacitor for about £8.50 from Maplin and it runs like a good 'un now.

The new capacitor is slightly fatter so I had to adjust the plastic cover to stop it interfering with the fan blades.

I found the feed pipe to the tank was leaking badly from a crack at the base of the flare. I just cut the pipe back and managed to reflare it with a Draper brake pipe flaring kit.

I just need to tweak the pressure switch settings now. I don't know if a previous owner has fiddled with it, but it cuts in at 5.5bar and doesn't cut out until 9 (should be 8).

 

[tigler]

Nice one ! Good to hear that the forum helped to diagnose the problem and that you repaired it. Pressure switch is easy to adjust, you will see a bolt under the cover with a + to - marking on it, turn it towards - to reduce the cut out pressure.

 

[Punx0r]

Unfortunately, the pressure switch only had a single adjustment. So reducing the cut out pressure to 8 bar dropped the cut in pressure down to 4.5bar

 

[roofman]

Unfortunately, the pressure switch only had a single adjustment. So reducing the cut out pressure to 8 bar dropped the cut in pressure down to 4.5bar

cheap as chips now mate
http://www.ebay.co.uk/itm/COMPRESSO...Air_Tools_and_Compressors&hash=item415f2fe7c0

 

[Punx0r]

Wow, that is cheap!

Only one more thing I need now is an air filter assembly. I can't find any trace of airmaster spares on google, and the only filters on ebay are 3/4" thread.

I've measured the OD of the remains of the old male threaded part and it's 5/8". Google indicates this makes it a 5/8" thread.

Any pointers, guys?

 

[eil]

Don't think it will be 5/8", when you measure bsp as a rule of thumb you need to subtract a 1/4", so I'm guessing it will be a 3/8" bsp fitting you have.