In 4510 are Sun Frost model R19 refrigerator and model F4 freezer.

Diagnosing the temperature sensors:  with an ohmmeter, check that
their resistance is in the range of 12,000-40,000 ohms.  If it's
outside that range, it must be replaced.

Replacing refrigerant in the R19:  Total content is 2 oz.
If the fridge no longer gets cool, it probably needs an ounce.
Buy a 12-oz can in an auto supply store.  Get the kind with
"Stop Leak" additive.  Coolant leak is probably in the 
copper tubing embedded in fiberglass in the fridge walls.
Cannot be replaced.

The R19 consists of copper tubing, condenser, evaporator,
cabinet, compressor, thermostat.  Sun Frost built all the parts
except the compressor and the thermostat.

Larry Schlussler  (707) 822-9095
Arcata, CA
larryssolar@gmail.com

Refrigerator/Freezer Dimensions
      H     W   depth  CF
R19   66" 34.5" 27.75" 8.07 cu ft
R10 43.5" 34.5" 27.75"
R4  31.5" 34.5" 27.75"
F4  31.5" 34.5" 27.75" 3.91 cu ft

Add 8" to height for clearance for ventilation

R19 $3200
F4  $1800

Photo:  https://www.dan-keller.com/4500/SunFrostCustomRefrigerator.html