Vevor / Yong Heng relay / breaker / thermal protection

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bubbahotep

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May 11, 2025
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My Vevor Yong Heng clone kept blowing the builtin 20 amp breaker. I didnt measure current yet, but based on the builtin voltmeter it didnt seem to be overcurrent related.

The orientation of the contact pads on the breaker in relation to the piston vibration seems to be the culprit (contacts bouncing up and down). I believe the autostop yong hengs suffer a similar problem and is why they blow relays.

My fix for now was to rotate the breaker 90 degrees or replace with a non resettable fuse. For the yong heng relays it might be worthwhile to get a vibration rated relay if you cannt remount the relay.
 
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bubbahotep said:
My Vevor Yong Heng clone kept blowing the builtin 20 amp breaker. I didnt measure current yet, but based on the builtin voltmeter it didnt seem to be overcurrent related.

The orientation of the contact pads on the breaker in relation to the piston vibration seems to be the culprit (contacts bouncing up and down). I believe the autostop yong hengs suffer a similar problem and is why they blow relays.

My fix for now was to rotate the breaker 90 degrees or replace with a non resettable fuse. For the yong heng relays it might be worthwhile to get a vibration rated relay if you cannt remount the relay.
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Breakers are a finicky mistress, the more they blow the weaker they get. I highly recommend everybody running Chinese compressors own a multi meter (dmm) with an ac/dc "amp clamp" so you can measure current without interrupting the circuit. Plus most meters can't handle more than 10 amps thru them anyhow and it's a contact measurement which opens you up to accidents and shorts.

You can get a cheap meter off Amazon or buy a nice one if you intend to use it more and want higher resolution data.

I bought a used fluke data logging 289 (1/3 of msrp) and a Chinese accessory ac/dc amp clamp because I do relays and high frequency parts for maintenence on old timer logic machines at work sometimes. It's high resolution data and useful for checking motor windings in these little compressors for shorts...
 
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Was drawing 11 amps but I didnt leave the meter on for long. The 'breaker' is a spring loaded bimetallic strip that pulls away from the contact when it gets hot. Arcing pits the contacts everytime it trips and it would go off in about a minute or two even after letting it cool off overnight. Replaced with same size breaker oriented up and down instead of flat, made sure all connections are seated and its not tripping anymore and I was able to fill my 6.8l from 2800 to 3400 psi, final temp of 32C in 20-30 mins (afraid pump burst disc will go if i try any higher pressure)

Whats annoying is the run capacitor is just loose in these things and flops around making a racket, the case is too small to put it in the proper screw mount on top of motor. Wrapped the capacitor in masking tape and superglued it down (glue wont stick to the capacitor plastic). They use a CBB60 120uf capacitor.
 
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Should be able to try fix without opening case. Loosen the nut, rotate the breaker 90 degrees by grabbing the flats and retighten nut.

I did that and used this replacement part (had to open case and ream out hole a bit to fit):

At some point they switched from 13 amp to 20 amp breakers.

1000000943.jpg
 
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