Defrost Timer Test

TM 10-4110-262-13&P

0029 00

Defrost Timer Test

The defrost timer initiates the defrost cycle.

1. Verify that the evaporator coil temperature is lower than 36 5.4 F, otherwise jump pump the mechanized

terminals.

2. Set the Defrost Timer to approximately 1 minute: A: ↑, B: ↓, red round selector position 4.

3. After approximately 1 minute, the defrost must be initiated: Defrost LED, Defrost Relay, and Solenoid Valve must

be activated.

Defrost Termination Switch (DTS)

If the ADR-300 does not switch to the defrost cycle, the problem may be defective DTS or a fault on the printed circuit

board. Test the DTS as follows:

NOTE

The DTS closes at 36 F 5.4 and opens at 48 F5.4.

1. Confirm that the evaporator coil temperature is below 365.4 F.

2. Unplug DTS terminal connector located near the TEV sensing bulb.

3. Place a jumper wire between the two terminals of the DTS harness.

4. Press the manual defrost button. If the ADR-300 shifts to defrost, the DTS is defective.

5. If the ADR-300 does not shift to defrost, proceed to the next section to isolate other defrost problems.

Other Defrost Problems

If the ADR-300 does not switch to the defrost cycle, first test the defrost termination switch as outlined above. If the

ADR-300 does not shift to defrost:

1. Open the RU electrical enclosure and check 24 VDC between connector C3 (Terminal 1) and connector C3

(Terminal 2).

NOTE

Terminal 1 is positive and Terminal 2 is negative.

2. If 24 VDC is detected, then replace the defrost relay (D).

3. If no voltage is detected, skip to step 5.

4. Initiate a manual defrost if the RU still fails to defrost then replace the PC board in the RU control box.

5. If 24 VDC is not detected in step 2, check for voltage between C3 (Terminal 1) and the main unit ground.

0029 00-13