Air Compressor - won't start - where to start looking

I bought myself an old Sherry 50litre air compressor a couple of years back on fleabay - saw it start up and work OK from cold start up so bought it. Until tonight, it's been stored in my shed waiting to be used in anger. Got it all rigged up with the tyre pressure gizzmo, plugged it in and nothing. I know the electric socket that it was plugged into is OK and I've changed the 13amp fuse in the plug. Took the cover off the switch gear and all the wiring looks OK.
So before, I start taking bits apart, is there normally a component somewhere that would give issues if not used for a long time. Mate down the road said try the switch gear. I've got a multi-meter to put across a few terminals to see if it's getting electric where needed but other than that, I really haven't got a glue.
Guess it's a matter of putting the meter reader on volts and seeing if there is any current going through. I'm not going to spend money on it because it only cost £20 to start with, but before I throw it in the skip, thought I might have a little dabble to see if I can get it working again.

can you turn the pulley wheel round manually Pete? The piston might be seized from standing so long.. :wink:

As Kel said, it will be stiff, top up the oil with compressor oil and hand turn it a few times, chances are it will free up, this usually happens if they have been sitting a long while, mine does it all the time.

Sounds like it might be a direct drive one pete, that has no visible pulley...
Have you got a meter to test that the start unit is sending a supply to the motor...Most compressors have a start unit which incorporates a pressure cut out, and I think the start capacitor too (I am guessing it runs and induction motor).

Appreciate replies guys but I can't see how to turn it by hand - it's not belt driven or got a pulley wheel. Just an electric motor with a air intake segment (looks something like a motor bike engine). I think the best thing I can do is post a picture 2moz when I've got better light to see if I can establish where to put the oil and turn. It's quite an old air compressor without an micro chips on it, only solid state connectors.

pics would be good pete... :wink:

Reckon its shaft drive below the cover Pete, most of the ones that sort of size are fella. You just have one cover that kinda goes over the motor and part of the compressor part.

Does it have a cover fitted over it? If so, remove it and you will see the pulley / belt etc.
I had the same problem a while back, in fact i put a thread up on here.
It turned out to be an air filter breaking up and the wee bits had been sucked into the intake.
Took it out and removed the bits, and it fired up right away.

Here you go, just found it.
viewtopic.php?f=32&t=41967&hilit=+air+compressor

Here we go chaps - pics of the non-starter:

Can anybody see if there is a shaft, pulley that I may need to turn to get it going?
Just taken the air filter cover off and the filter is as clean as.
Found the filler neck for the oil, just need to establish what oil and fill as necessary.

Last edited by nigelbread on Thu Oct 20, 2011 10:09 pm, edited 1 time in total.

Hi this looks like a very good quality unit.
The pump is unlikely to be stuck.
If the pump is stuck you would hear the motor humming as it tried to run, if left trying to run the motor would get hot and trip out.

If your knowledge of electrics is limited I suggest disconnecting the power cable at the motor and fitting a 3 core power cable and plug direct to the motor.
This will bypass the auto off so if it runs be ready to switch off on the socket.

The capacitor which lives on top of the motor has a dent in it but this will not prevent it working.
A failed capacitor usually bulges and leaks. Can be tested with an insulation tester [or a capacitor tester]
If it had failed the motor would hum but fail to rotate.

It is advisable to remove the inspection plugs at the end ofthe reciver [let all air out first] and using a torch check inside for any deep pitting or corrosion that might weaken the tank.
Looking at the outside does not realy tell you much.

Cheers nigelbread - I'll have a fettle and see what I can come up with. It is a heavy bit of kit

Looking at the pics, and I am only guessing in the extreme here, but would the part with the large "SHERRY" sticker be the electric motor housing which would have a shaft going to the circular part below the gauze type filter be the actual compressor rotor housing?

What the square box part does I do not know unlessit is a pressure relief device (maybe???????) prior to the main tank?

I am only guessing but judging from the pics. I am not a compressor engineer and only offer as observations.

Unplug it. open the 'square box' and remove the small plate covering the motor connections (located adjacent to the cable entry point) then using a multi-meter set to ohms check the wiring from the plug, through the on/off switch, over pressure switch, nvr starter (if fitted) up to the motor. Make sure all connctions are tight at the same time.

Stay safe, do NOT work live (with it plugged in and the leccy on) unless you know your way around elecrics (and if you do know your way round electrics then you won't work live anyway).

Thoughts would be:
1. Blown fuse - U/S Motor, capacitor down to earth, conductor pulled out of it's terminal in the square box.
2. Break in cable (compressor end most likely caused by the wheels running over the cable and stretching it).
3. Knacked contacts on the pressure switch.
4. Stuck contact carrier in the nvr contactor if fitted.
5. Burnt out coil in the nvr contactor.
6. If direct start (no contactor) a burnt out main switch.

Last edited by Retro Pedro on Sat Oct 22, 2011 7:28 pm, edited 1 time in total.

Goods news is that I've found the problem - the main switch is a spring loaded mechanism and if I take the wiring connector box out, and reset the switch and mechansim to the 'on' position and plug it in, it runs. However, if I switch it off on the switch, then back on, the spring loaded trip will not reset. So the answer is to reset all the components to the 'on' position and just keep activating it with the mains plug making sure the switch is left in the 'on' position.
The bad news is that I don't think it is all that. Left it running for about 1/4 hour to build up pressure and it didn't have enough umph to blow the tyres up on my Sedona. Either that or the brand new tyre attachment that I got in the Aldi offers sale is naf. Although I had air pressure, it didn't seem very high.
I also filled it up with some proper compressor oil, 9/10 of a litre went in. Now I've got a fountain discharging oil out of the small holes in the filler neck. :oh yer:

Hi remove air filter and run see if you have a blow back from the inlet as a common fault is dirty inlet valve.
Next step is to remove cyclinder head plugs and inspect valves.
The type of tyre guage you have has to be pushed firmly and held on to the tyre valve.
How much pressure did the tank guage show?

What is marked on the ID plate?
close up Photo.