Compressor advice

[E-bmw]

Some months ago I was gifted a small (25 litre) sip compressor in 1/2 decent working condition but I came to use it for the first time since today & just get a mains hum when turning it on, so immediately turned it off.

I am no expert but am assuming it is likely to be 1 of 2 things.

Motor/compressor seized.

Motor stalled.

As I am away at work for the next 2 weeks can't do anything until then but just thought I would seek the advice of any people with better experience of these than me.

Am I on the right path? Am I missing anything?

[paintman]

Apart from the above:
Pressure switch faulty? - the one that turns your compressor motor on & off automatically.
Capacitor failed?
Relief valve not operative? (The pssh you hear when a compressor shuts off when full)
At the end of a very long extension cable? ( A bit off the wall but I've experienced this at two places I've worked at, one had a very long cable spur run to the end of their yard & if I plugged in it wouldn't kick it over. The other one just has too many electrics in their workshop & sometimes just one more power tool switched on by their staff will trip the circuit breaker )

Edited by paintman on Wednesday 30th October 20:41

[alabbasi]

If the mains hum, it's either wired wrong or maybe maybe brushes are out. Is it belt driven? Try removing the belt and seeing if the compressor motor and pump turn by hand then come back to us.

[Novexx]

Does sound like it's seized & this wouldn't be unusual for one that's been sitting around for a while - turning over by hand before starting can often resolve this.

If it turns over by hand (well maybe a spanner on the shaft), but still hums, it could be the start capacitor.

If it won't turn over by hand, possibly a faulty unloader valve (if fitted) or a s****** up cylinder.

[alabbasi]

Novexx said:

If it turns over by hand (well maybe a spanner on the shaft), but still hums, it could be the start capacitor.

'
Yep, this is probably the first check.

[E-bmw]

Thanks for the answers guys, it did run when I picked it up, so hopefully not seized, & not wired wrong, but capacitor is possibly one to check also when I get back to it.

I will pick one up if I can find the rating of them as I know they can't really be tested.

[guards red]

You're not turning it off too soon are you? Sometimes the hum for a couple of seconds before the kick in...

[DVandrews]

alabbasi said:

Novexx said:

If it turns over by hand (well maybe a spanner on the shaft), but still hums, it could be the start capacitor.

'
Yep, this is probably the first check.

That would be second on my checklist, first would be a hand turn on the compressor..

Dave

[E-bmw]

guards red said:

You're not turning it off too soon are you? Sometimes the hum for a couple of seconds before the kick in...

I'll stick with turning it off immediately as I do know that if the motor is stalled the start-up current (which can be many times the running current) will keep flowing through the motor until something blows.

[InitialDave]

If it's been sat for a while since you last ran it, it could be a bit of gumming up of the cylinder or slight corrosion from moisture.

I'd drain the cylinder, see if anything nasty comes out, check the oil level on the dipstick/sightglass (unless it's oil free), and maybe squirt a little bit of oil directly in through the intake. See if it runs then.

[E-bmw]

InitialDave said:

If it's been sat for a while since you last ran it, it could be a bit of gumming up of the cylinder or slight corrosion from moisture.

I'd drain the cylinder, see if anything nasty comes out, check the oil level on the dipstick/sightglass (unless it's oil free), and maybe squirt a little bit of oil directly in through the intake. See if it runs then.

I did check the oil but I will I suspect be doing all of the above pre-the next try & turn by hand, check again, put some oil down the piston & then see what happens.

[Graculus]

Have you opened the drain valve to ensure there isn't any water in the reservoir? It takes a surprisingly small amount to prevent mine running (admittedly, I don't recall it making a humming noise at the same time).

[tapkaJohnD]

My compressor used to blow the 13A fuse on the plug, as any electric motor draws a lot more currnet at low speed, as it starts up. It's now wired straight into the wall, and relies on the ring main circuit breaker, which never blows.

And it has a ?thermal cut-out in its own circuit box. It's a tiny switch on the cover, easy to miss, just flick it back and it works.

John

[E-bmw]

Graculus said:

Have you opened the drain valve to ensure there isn't any water in the reservoir? It takes a surprisingly small amount to prevent mine running (admittedly, I don't recall it making a humming noise at the same time).

It is definitely fully drained as the drain was left open from when I collected it.

[E-bmw]

tapkaJohnD said:

And it has a ?thermal cut-out in its own circuit box. It's a tiny switch on the cover, easy to miss, just flick it back and it works.

John

That is something I didn't look for, good spot, would that potentially cause these symptoms?

[E-bmw]

Just to finish this post in case it helps anyone out.

It seems it was just a bit stiff to turn by the motor alone, a quick turn by hand & a drop of oil & it is fine now.

Thanks for everyone's suggestions.