Replaced defrost heater, temperature and defrost limiter thermostat. After taking the cover off the air chiller I found the coils frozen solid and defrosted it with a hair dryer. Once defrosted I remover the heater coil to test it it was fine, then I could see the defrost limiter was broken and as I put the unit back together I broke the heater tube (it is glass) so I ordered all the parts that might be defective and replaced them for less than the charge of having some one come to check it out.