Westinghouse 44SK Hot Compressor

[ss540]

I'm troubleshooting a refrig system on a friend's W44SK.  The compressor would not start when I first tested the machine.

I checked wiring and replaced a badly deteriorated power cord.  The compressor still would not start.  I jumpered across the overcurrent device, and the compressor started and the unit cooled into the mid 30's in the cold box.  But, the compressor skin temperature was too hot to touch after about 8 minutes.  I measured 145 f, using a contact type temperature probe. The condenser fan and evaporator fans are running and the air flow of comp fan is across the compressor.  There is no obstruction in the condenser or evaporator coils.  I ohmed out the compressor and the values are correct per a post I found in the Refrigeration forum.  There is no continuity between any of the 3 pins and the compressor case.

The thermostat is a three wire type, which I am unfamiliar with.  Of the 6 machines that I have, all are two wire type thermostats.  I do not see a start/run capacitor on the unit.

I am at the limit of my troubleshooting knowledge, so can someone advise me on what to check next?

[johnieG]

I would do a current draw on the compressor & compare it to the name-plate / listed current,

as an example, if the name-plate states a rated current or FLA ( full load amps) of 4.5 amps at the given voltage say,  typically 115/120volts that's what it should be around once it's up & running, it will be naturally a bit higher upon initial start up. if it's pulling higher amps then it's either has a tight compressor or the start winding isn't dropping out, either way it's heading for a burnout or lockup and it will be time for a new compressor.

[ss540]

Thanks Johnnie, I will check the current draw when I get back in town.  I think I still have a clamp on ammeter. 
Since the thermostat is a 3 wire unit, would it also function to dropout the start winding?  I'm not familiar with a 3 wire thermostat.

[johnieG]

Thanks Johnnie, I will check the current draw when I get back in town.  I think I still have a clamp on ammeter. 
Since the thermostat is a 3 wire unit, would it also function to dropout the start winding?  I'm not familiar with a 3 wire thermostat.

Nope, that would be silly,     the third wire was typically used as a small heater to keep condensation out of the housing when they had mounted the thetmostats indide the cold area, not the best idea if you think about it,  ever notice that all earlier T-stats are located outside of the cold area?

Simply use your ohm meter to see which pair of wires are for the control contacts,  there is a common wire & a switched wire, you may use a can of duster spray as a source of cold "freeze" spray by holding it upside fown & spraying it on the T-stats sensing end to test the unit.

[ss540]

I checked amp draw on the compressor and it is pulling 3.5 amps on the red wire, 4.5 amps on the black wire and 8 amps on the white wire.    Curiously, all three of the wires go through the thermostat housing.  With the exception of the Klixon, there is no other control circuit or device.  The thermostat contacts break the white wire and black wires, but the black wire goes through a winding first.  It appears to me that the start winding is not dropping out after startup.

The refrig unit tag is pretty beat up, but it appears to say 4.5 full load amps.