Compressor probs ...starting when hot...well not actually hot....

[clogs]

OK, inherited this comp from an old friend who's no longer here....it was hidden under tons of sawdust n cobwebs.......he gave me a few bit's that I treasure....
obv not been used for years......made in old Germany - Austria.....
sorry about the size of the photo's....

it's sweet thing, slow and not too noisey but unfortunatlely it's direct drive.....
when the tank is empty it's starts up fine ^I have replaced the start switch for a new one, the cover was broken and taped up,
the new one is bigger rated amp wise than the old one...^example if it was 10 it's now 15) which is what I do everytme I replace a switch, without probs....
I'm out of stock now but usually buy 2-3 switches at one time....
anyway,
once it kicks in at the lower pressure it wont start...it just hum's.....
if u drain the tank to almost empty it will re start no probs......I have removed and cleaned the non return valve on the tank twice....both times cleann no rusty debris....
there is a trip button, when pressed it will start up sometimes but this switch is faulty, guess over the years it's contacts have worn out....it's a bit hit n miss when u press it.....no idea on it's tripping load....
Have removed this switch temp.....temp hot wired the switch .......will buy a new one.......
Now, it has 2 capasitors....physically one is bigger than the other so I guess one is start and the other is run....is this correct....?
do I have a faulty capasitor.....?
here's a few pic's of this and the wiring....
PS the wiring is as I got it.....apart from the temp join for the cut out /overload switch....

a couple of things.....bad design of capacitor location...this wil get modified.....will place them in an enclosed plastic elec box.....^the smaller capacitor has a few v/small dents...being the outside one.)
I could put a dump valve on the tank so that I can use it but I want it to do it's thing in the corner....
if it had a seperate motor would just replace it and worry about the prob later.....add to the to - do list.....hahaha

Ok, lastley.....if I need new capsitors, no problem but they will prob come from the other end of the island a 2,5'ish hr drive away......just wanna get every thing in one go....
it's to good a comp to bin it and don't mind spending a few Euro's to get it working....
any advice/ tests please....
ta.....

 

[clogs]

this didn\y get on the list for somereason....
can anybodyhelp pls

 

[flh801978]

Is the pressure relief valve working on the pressure switch?
You should hear a hiss from the switch when it switches off at high pressure…thereby making the pipe from compressor to tank at no positive pressure.

 

[sawtooth-9]

Agree with flh801978, if it starts with no tank pressure, looks like the motor would be ok.
If the pressure relief valve on the pressure switch is not working, you are asking the motor to start with a full pressure load - not good.
I would replace both capacitors and fit a new pressure relief switch anyway.
Although unlikely, you could check the condition of the windings by using a mega to check the resistance between the line and earth. If this is poor, the motor will lack power and eventually fail.

 

[cowtown_eric]

pressure relief valve also called the unloading valve, it's failure will do exactly what you described.

It unloads the pressure on the heads. If motor starts, yer caps ain't likely bad, so don't go there yet..

Eric in the colonies

 

[sawtooth-9]

pressure relief valve also called the unloading valve, it's failure will do exactly what you described.

It unloads the pressure on the heads. If motor starts, yer caps ain't likely bad, so don't go there yet..

Eric in the colonies

Agree the caps MAY not be bad
You can check their performance ( to a degree ) with a multimeter.
But ...
Capacitors are cheap, and these look old and may not be performing to spec. under load. So I would replace them anyway - just to eliminate a potential problem and take a wise preventative measure. Cheap and easy - so why not do it ?