How long do you persist with a repair?
I found a small (about the size of a Cobb loaf) oil free, medical compressor by the side of the road about 5 years ago and brought it home and put it under the house.
Saw it the other day and pulled it out as SWMBO has flagged with me that she might like to do a bit of air brushing.
No cord, checked continuities and earth, all OK.
Add new cord - check switch - dubious operation - sometimes it made contact other times it didn't - pulled switch apart - corroded - tried cleaning but no go, so replaced it with a similar spare I got from an electrical heater.
Gingerly switch it on - draws 1.6A but nothing happens.
Take it apart and find a piece of the internal plastic fan vane has broken off and jammed the motor.
Remove said plastic - Whala! it runs.
Very quiet, but bugger all air coming out.
Added a pressure gauge and found it produced a max of a whopping 12PSI - checked what little external plumbing there was for leaks - nothing.
Pulled pump head apart and found some corrosion on the reed valves and valve seats and cleaned these up, They were almost bad enough to warrant replacement (have done this before using bits of soft drink can) but decided to see if I could get any more pressure, nope no better.
Before I had time to reattach the pressure gauge there was a "CRACK" and bit of grating noise and the adapter board breaker kicked in.
Pulled motor apart - another plastic vane had broken off and jammed the motor. The newly broken vane was opposite the other broken one so I though - well they will balance themselves out.
On the next restart another vane broke almost immediately, jammed the motor and tripped the breaker.
At that point I felt like chucking it in the e-waste bin but before I did that, I recovered the switch, cord, bearings and a couple of SS plumbing fittings. All in all I must have wasted about 5 hours on the wretched thing.
I would have better off binning it in the first place.
Sometimes you will sometimes you lose.
