Dead compressor - any tips?

[TriumphDriver]

I have a SIP AS 3/200 compressor - 3 HP, 200 litre, single phase. It has recently refused to start. The motor will not turn over at all, and there is absolutely nothing happens when plugged in or switched on - no humming buzzing or other noises.
It's currently drained, and I've replaced the main fuse in the plug. Is there any sort of failsafe switch, or a reset that may require resetting? Sump is full of oil, head bolts are all tight and it's not a very old compressor.
Any tips would be welcome!

[Luxobarge]

Mine does that occasionally - there's a black box near the regulator that is the pressure sensor, i.e. it switches it off when it gets up to pressure. If I give this a bit of a slap it normally leaps back into life - I think the moving contacts have got a bit sticky and it sometimes sticks open. The main unit's on-off switch is on this black box too, and I think the problem is related. I really should take it apart and sort it out properly, but you know how it is, not enough hours in the day!

Yours must have some sort of pressure switch unit thingy, I'd start with that if I were you. If you want to prove it, you can use a multimeter and test for continuity right up to the compressor motor.

Hope that helps!

[tractorman]

I'm not 100% sure, but there may be a starting capacitor on the motor (it depends on model as to where and what). This can fail and give similar symptoms.

Check Luxo's idea first (mine old one used to have the problem) before spending cash!

Since old one fell over two years ago, I have the opposite fault - I have to hit the thing to stop it when I switch the mains on at the socket - then I pull the on/off button out! I must repair it sometime!

EDIT: I should add that it works properly once I have started it - the pressure switch cuts power as it should! NEVER run one with a faulty pressure switch!

[suffolkpete]

I'd go with the pressure switch theory. I had the same problem on mine recently and it turned out to be dirty contacts on the pressure switch. If the start capacitor fails, or the centrifugal switch that disconnects the capacitor when the motor is up to speed, then the motor will hum and get warm.

[StephenL]

All the compressors I and my dad have, have a reset button. This had me scratching my head until I found it. My dad was about to break his draper compressor for spares because it was" dead" when I suggested the reset button he didn't know about. It works fine now!

On the inside of the plastic cowling that surround the cylinder it was. It is a push fit into a hole that is part of the alloy casing of the cylinder (where the cooling fins are).

I had other problems with simple wiring connections that had come out. Might be worth tracing all the wiring so see if you can find an obvious problem.

[TriumphDriver]

Thanks for all the pointers, wish me luck - off work tomorrow so compressor here I come!

[TriumphDriver]

IT WORKS!! HALLELUJAH or other wierd middle-Eastern words, Gaddafi or Taliban or whatever sounds suitably wondrous.
Here's how to fix a dud compressor:
Swear when it doesn't start. Change the fuse. Change the fuse in the 4' extension lead. Swear again. Test the extension lead with another electrical item, it works fine. Change the compressor fuse again. Check the plug - it looks a bit worn, change the plug.
Strip down the push-start switch box. Test electrical connections - nothing. Decide tester is dud and press on. Clean and replace air filter. Remove fan cover and spin fan and belt, no problems. Rebuild. Still no start. Dismantle small box on top, find white cylinder and a push button assembly. Clean and replace as found. Still no start. Remove small plastic pipe that runs to on-off switch box, clean, blow through and replace. Remove brass assembly below start switch box. Clean and replace. Still no start.
Check plug again. drop plug, out pops fuse under one of the cars, replace fuse with other handier fuse.
IT WORKS!
Out of a box of ten 13 amp fuses from my local electrical store, I've found four duds. Three in a row were what I used in the compressor, one after another, which caused a lot of head scratching and this thread.
I'm off to buy a new 240 volt tester which would have told me it was the fuse in the first place. At least everything is nice and clean now.