Hello all compressor question on Vendo Vertical 6 machine

[Arch Stanton]

Hello all compressor question on Vendo Vertical 6 machine. I just rewired installed new fan on the lower deck lights and cleaned it up. The machine cools very well seems to fluctuate between 28-34 on setting 4 the only thing is when the compressor starts up it makes a hammering knocking sound for a couple of minutes then goes away I did install a new capacitor combo to give it a boost. I have not replaced the thermostat as it seems to work. Anyway maybe you guys have a few suggestions? I have also checked the other upper deck fan it works with no issues

Thanks Joe

[johnieG]

Hmm, a 60+ year old compressor's making noises you say... how odd! 

Seriously though, "sounds" * like a mechanical problem inside to the compressor itself, not electrical, probably a broken isolation spring ( think of it as an internal shock absorber ) it will cause a hard knocking mentioned usually on startup or shut down,  you are hearing the internal "guts" smacking the inside of the compressor housing due to the reciprocating motion of the piston & connecting rod.

Sometimes the compressors piston will rock back and forth inside the cylinder causing a similar sound but with a bit more of a "buzzing" tinny sound, this noise may quiet down once the compressor gets up to pressure as the freon gas acts like (again) a shock absorber.

Nothing can be done about either situation, it's just a old compressor. Also check for loose or missing rubber support feet and/or springs that keep the compressor from vibrating against the deck plate, etc.

*= pun as a matter of circumstance