Table 4-2. Unit Troubleshooting-continued -706880264

TM 5-4210-233-14&P-1

4-2. Unit Troubleshooting-Continued

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

ELECTRICAL SYSTEM - AERIAL CONTROL PANEL - Continued

12 LADDER INTERCOM DOES NOT FUNCTION PROPERLY - Continued

Step 3. Check continuity of audio wires 1291 and 1292 between intercom unit (on aerial panel)

and intercom speaker (at ladder tip).

Replace wire. (see para 4-9.4)

Step 4. Check internal fuse inside intercom unit for continuity.

Replace fuse. (see para 4-9.4)

Step 5. Check intercom for proper operation with 12V applied across terminals.

Replace intercom unit (see para 4-198).

13 LADDER TIP SPEAKER DOES NOT FUNCTION PROPERLY

Step 1. Bypass traveler cables using jumper wires and check remote speaker for proper operation.

If speaker operates properly, replace traveler cable (see para 4-206).

If speaker does not operate properly, replace ladder tip speaker or refer to "ladder intercom

does not function properly" troubleshooting procedure.

14 AERIAL LADDER HOIST CYLINDER LOCKING VALVES DO NOT RELEASE LADDER WHEN

RAISE/LOWER CONTROL IS PLACED IN "LOWER" POSITION

(Refer to Electrical Wiring Diagrams, Appendix H, Sheet 1O of 16.)

Step 1. Check aerial elevation control limit switch (on manifold block raise/lower control) for proper

operation. Switch is normally activated when control lever is in neutral position. Should

disengage Immediately when control lever is moved to "lower" position.

Adjust/replace switch (see para 4-9.4).

Step 2. Check that valve releases properly when 12V is applied to solenoid coil.

Repair/replace valve (see para 4-9.4).

Step 3. Check for +12V at aerial circuit breaker #5.

Replace breaker (see para 4-99).

4-135