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Freightliner Refrigerator Troubleshooting Guide
750000005 (TJ18F)
750000011 (TJ22F)
750000026 (TJ18FP3)
DOMETIC CORPORATION, ENVIRONMENTAL DIVISION
P.O. Box 15299 I Richmond, VA 23227 USA
Phone +804 746 1313 | Fax +804 746 7248
www.dometic.com Page 9 of 20
Specific Trouble-Shooting of
Electrical Components
A: Check incoming voltage
1. Hold multimeter leads to the positive (+) and negative (-) terminals of the load dump
module. The red lead from the multimeter is held to the “+” terminal and black lead
from the multimeter is held to the “-“ terminal. You should read positive voltage. If
the reading is negative, check DC polarity. If it is reversed, correct wire
connections.
2. The inrush current must not drop the voltage more than 3% or .36 volts when the
compressor is initially energized. Monitor this voltage by using a multimeter at
start-up. For 12vdc system, the cutout is around 10.4 volts and the cut-in is 11.7
volts. If there is a drop in current, at start-up, below the cut out voltage, then the
compressor will not operate. A drop in voltage will occur if the wire size is too
small or poor connection.
3. Verify that voltage at unit is equal to voltage at source. If the voltage is less than at
the source then the wire used from source to unit is too small.
B. Checking the Compressor
1. Remove all wires from compressor module (make note where they are connected).
2. Removed Danfoss module from the compressor by removing the mounting screw
and twisting the module to the rear to disconnect it from the compressor. See
Section A #12 in “General Troubleshooting” Section.
3. Compressor windings can be checked for defects by measuring the resistance on the
current lead-in pins. If the measured values between all pins are approximately the
same (approximately 2.2-2.5 ohms). The compressor motor is OK.