Replaced compressor but it only runs about 15 seconds and shuts off

[fixbear]

First off, Mastercraft  does not make compressors.  And most of this model had Tecumseh 4000 BTU high temp High starting load, R134 compressor.  One CAN NOT remove a compressor for one unit and install it in another unless it is the same capacity, lubricant, refrigerant,  motor spec,  and voltage.

 

Why was the original replaced?

Does the unit have a mechanical or digital temp control?

Who did the replacement?

 

Now dig out your DVOM.  Measure wall voltage.  Measure compressor voltage and watch to see if it drops off at cut out or the compressor stops from overload. Alternately you can measure the compressor amps.   Following is the Tecumseh motor electrical for a AE4440-AA1A compressor that belongs in the machine.

Now, if the power drops at the compressor,  you have a control problem. Either a connection or thermostat.  If you have a electronic temp control, you may have a sensor problem.

 

If the power stayed on it will be the overload going open.  Check fans and condenser coil to be plugged.

[ectofix]

fixbear wrote:

 

If the power stayed on it will be the overload going open.  Check fans and condenser coil to be plugged.

Is there a service valve?  If so, it might still be front-seated – done during the compressor change.

[toon]

My apologies it is a Masterbilt MB03-15426 baught at Partstown, their aftermarket replacement for the Tecumseh AE4440Y-AA1A.

It was replaced because the original compressor did not work and system had no freon, which is another issue to fix once compressor is fixed to find leak and how bad a leak it is, It has set 2 years unused.

Thermostat is mechanical.

Local refrig repairman replaced. 

[fixbear]

OK,  You have a Tecumseha AE4440.  very common compressor.  Make sure it is 115 volt.  Mechanical thermostat.  Is it set to the middle?

 

Before any repair with no charge, one has to find the leak for the evaluation of the repair.  Sometimes one can buy a new machine for the cost of repair.  Not seeing your compressor compartment,  it is possible that someone added a suction pressure control.  But there is not a lot of room in a keg machine. It would look like this;

If that was added as a workaround to freeze up or temp control due to a wrong thermostat it would explain the short cycling.  Low charge.  But one never puts such a control on a cap tube metering system.  It just won’t work because of no direct stoppage of refrigerant in the off cycle. Legally your tech can not walk away from a machine with a leak after charging. So they would have either not charged it or repaired the leak. 

 

It is also possible under the conditions you state that the filter dryer was not replaced.  Being open (you leak) for 2 years would allow moisture to enter the system. Causing a ice plug at the beginning of the cap tube blocking the system.  But normally the condenser would hold the measured amount of R134. If it was not measured then it can sustain a overcharge again overloading the compressor.  Even deep vacuuming for a hour with a saturated dryer will not remove all the moisture. And will cause saturated pellets of drying compound to explode in the dryer plugging to cap tube.

 

During compressor replacement, one has to vacate the system, purge with nitrogen, do your brazing with nitrogen purge to prevent any internal oxidation scale from forming. then vacuum below 700 microns and hold to test for leaks and remove any moisture.

 

On a side, True coolers often have special spec thermostats. Aftermarket A12’s or A30’s look identical, but do not always work right in a True. I’ve come across a lot of them over the years that have been replaced by others and created either short cycles, coil ice up,  or not shut off at temp. often they have to be bonded to the evaporator coil for defrost sensing.

 

The big question is does the compressor discharge line get hot?  Is air moving thru the condenser? 

[fixbear]

Ectofix,  Service valves became illegal in the 90’s on unit coolers. (EPA)  And a AE4440 isn’t sold with rotolocks.

[toon]

No Suction Pressure control boxFilter dryer replacedVacated-do not know if he used nitrogen to purge while sodderingHeld appropriate amount of r-134Thermostat set about 3/4 

 

 

Sent from my Verizon, Samsung Galaxy smartphone

[fixbear]

Then it comes down to troubleshooting it electrically.  Like a stated above.

 

Oh, and air flow/cooling.

[fixbear]

I should add here, that when the compressor gets power the condenser fan also gets power.  If the compressor is stopping but the fan still runs it will be overload opening.  If both stop together, wiring or thermostat. 

[ectofix]

I don’t know that unit’s setup.  If it’s a TXV with receiver, then I was merely suggesting that maybe the service valve on the receiver might still be closed.  That’d be a really dumb mistake by a tech, but a possibility nonetheless.  That’s all.

 

I don’t get why his local refrig repairman isn’t rectifying this problem instead the owner having to pursue it.

[fixbear]

Ahh,  The 64,000 dollar question.