312E, 312F, 313F, 316E, 316F, 318E, 318F, 320E, 320F, 323E, 323F, 324E, 325F, 326F, 329E, 329F, 330F, 335F, 336E, 336F, 340F, 349E, 349F, 352F, 374F and 390F Excavators and 336E MHPU and 349E MHPU Mobile Hydraulic Power Units Air Conditioning and Hea Caterpillar

Illustration 1	g02372017
(1) Air blend motor (2) Air blend dampers (R) Connector

Diagnostics

Illustration 2	g02372178
(3) Temperature select switch (4) Control panel

Illustration 3	g02520902
Partial Electrical Schematic (A) Connector (B) Connector (C) Connector (CC) Connector (D) Connector (DD) Connector (R) Connector (1) Air inlet motor (4) Control panel

1. Set temperature select switch (3) on control panel (4) to the Maximum cooling position.

2. Check for movement of air blend motor (1). If the motor moves, even a little, see Step 3. If the motor does not move, see Step 6.

3. If the error is still shown after the initial action has finished, see Step 4. If the error is not shown after the initial action has finished, the outlet air damper is locked or there is a problem with the linkage.

4. Disconnect connector (R) from the air blend motor connector. Measure the resistance value between the "BU/BK" wire and the "BR/RD" wire of the air blend motor connector. The resistance should be approximately 4.7k ohms. If the resistance value is correct, see Step 5. If the resistance value is incorrect, the air outlet motor is defective.

5. Check for continuity between the "BU/BK" wire and the "YL/BU" wire, and between the "YL/BU" wire and the "BR/RD" wire of the air blend motor connector. If there is continuity between the two sets of wires, the control panel is defective. If there is not continuity between the two sets of wires, the air outlet motor is defective.

6. Set temperature select switch (3) on control panel (4) to the Maximum heating position.

7. Check for movement of air blend motor (1). If the motor moves, even a little, see Step 3. If the motor does not move, see Step 8.

8. If the error is still shown, see Step 9. If the error is not shown, replace control pane (4).

9. Check the wiring harnesses between the air outlet motor and the control panel for continuity. If there is continuity, either the air outlet motor is defective, the air outlet damper is locked, or there is a problem with the linkage. If there is not continuity, the harness is defective.

Specifications

Resistance ... 4.7k Ohm

Voltage between connectors ... 5 VDC

Illustration 4	g02350723