Air Dryers—A-4400 Series Technical Bulletin
23
Check the condenser periodically for dust/particle buildup between the fins;
this buildup could eventually lead to a reduction in heat transfer. If there is a
buildup, remove it using a vacuum cleaner and a soft brush.
If there is power to the air dryer and the compressor is not operating, using an
ohmmeter and referring to Figure 13, check the electrical service as follows:
1. Disconnect the power supply to the air dryer.
2. Remove the screw terminal from the overload at 3 and check for
continuity between 3 and C1 on the overload. If there is no continuity,
the overload may be tripped. Allow 10 minutes to pass, then check again.
If there is still no continuity, the overload relay (Tecumseh 830-10041)
must be replaced.
3. Pull the relay off the compressor terminals (keeping the relay upright) and
check for continuity between 1 and S1. If there is continuity, the relay
contacts are closed when they should be open and the relay (Tecumseh
820-10052) must be replaced.
4. Check for continuity between 1 and M1. If there is no continuity, the
relay (Tecumseh 820-10052) must be replaced.
5. Check for continuity between compressor terminals C and M. At an
ambient temperature of 77
°
F (25
°
C), the run winding resistance across
terminals C and M should be approximately 3.1 ohms. If the run winding
resistance is drastically different from the above, either replace the
compressor or the entire air dryer.
6. Check for continuity between compressor terminals C and S. At an
ambient temperature of 77
°
F (25
°
C), the start winding resistance across
terminals C and S should be approximately 5.6 ohms. If the start winding
resistance is drastically different from the above, replace either the
compressor or the entire air dryer.
7. Check for continuity between compressor terminal C and the shell of the
compressor. If there is continuity, either replace the compressor or the
entire air dryer.
If all of the above tests prove satisfactory and the unit still fails to operate
properly, replace the relay (Tecumseh 820-10052). Doing so eliminates any
faulty electrical characteristics (such as improper pickup or dropout), which
cannot be determined by any of the above tests. If the new relay fails to
correct the problem, either replace the compressor or the entire air dryer.
Air Dryer
