compressor run 4 mins then off 7 mins

[sanya]

Hi there, i need your help
i'm working on refrigerator using r12 it's very old, the compressor using 3 in 1 relay, start capacitor and was run for for 3 mins then off for 7 mins and on for 3 mins again and again, But, both side fan is still runing only the compressor off and on, i checked superheat i got 36F and subcooled i got 31F and i also checked temp control it's working ok and nothing block the eaporator coil and the condenser coil, the onwer said he did replace the compressor 2 years ago...you think it's has restriction on the cap tube? or it's just low charge? but if low charge subcooled should be low right? or maybe 3 in 1 is bad? thank you vrey much for your help..

[icecube51]

what cind of compressor are we talking about ??? hermetic, semi-hermetic??? what regulates the cycle of the unit ??? is there not a start and stop timer,and if so,how are they regulated ??? is the compressor running hot and shut of on the temp safety device ?? if you want to now if it is low or high on refrig we need some pressure readings. also if the plant is used for cooling or freezing and what temperature is desired.

O yes, welcome on this forum.

Ice

[nike123]

.you think it's has restriction on the cap tube? or it's just low charge? but if low charge subcooled should be low right? or maybe 3 in 1 is bad? thank you vrey much for your help..

I think that compressor overload relay is acting.

Check for other symptoms to see if it is following case:

• SEVERE RESTRICTION (with excess refrigerant) = High superheat, subcooling, current draw & head pressure. Low suction pressure & indoor TD.

[lowcool]

it could be the relay or the compressors stuffed,but meter compressor windings to make sure they total ok,check current draw to see if its in excess of overload rating as this is what sounds like is happening and compare it to locked rotor amps.their is an equation to determine locked rotor amps by percentage value anybody out their who can help out with this ?