MAST AR 0314066 - Caterpillar

Introduction
This instruction addresses the polarity requirements of backlit rocker switches. When changing the illuminating lamp or replacing the entire rocker switch, perform the following procedure in order to ensure that your backlit rocker switch performs correctly.In backlit rocker switches, Light Emitting Diodes (LEDs) are often used to replace lamps. LEDs are comparable in price and offer a significant improvement in life. However, LEDs are polarity sensitive whereas lamps are not polarity sensitive. When replacing lamps with LEDs, perform the following steps to ensure that the polarity is correct before installing the LED. LED-backlit rocker switches are often used to replace lamp-backlit rocker switches. This is a simple procedure that involves removing a lamp-backlit rocker switch from a mating connector and then plugging an LED-backlit rocker switch into the mating connector. Before plugging the LED-backlit rocker switch into the mating connector, ensure that the mating connector's polarity is correct. Perform the following steps to ensure that the mating connector's polarity is correct.Polarity Check for Backlit Rocker Switch Connectors
Table 1
Tools Needed    
Part Number     Description     Quantity    
6V-7070 (1)     Digital Multimeter     1    
( 1 ) or comparable
Illustration 1 g00882164
Typical mating connector (A) Receptacle A (B) Receptacle B (C) Receptacle C (D) Receptacle D
Disconnect the Rocker Switch from the mating connector.
Use a multimeter to measure the voltage at mating connector Receptacle A and mating connector Receptacle C. The multimeter should read V+ on Receptacle A and Receptacle C. Refer to Illustration 1.
Use a multimeter to measure the voltage at mating connector Receptacle B and mating connector Receptacle D. The multimeter should read Common on mating connector Receptacle B and mating connector Receptacle D. Refer to Illustration 1.
If the voltages measured in Step 2 and Step 3 are correct, no further action is needed. If the voltages measured in Step 2 and Step 3 are not correct, perform the following procedure.
From the back of the mating connector, remove any wire (and receptacle) on which an incorrect voltage was measured (A, B, C, or D).
Replace the wire (and receptacle) that was removed in Step 4.a with a wire (and receptacle) that has the correct voltage.Note: In many cases that involve incorrect connector voltages, two wires have been inadvertently switched (or wired backwards). In a situation that involves two wires that have been wired backwards, remove both wires. Swap the wires so that the proper voltage appears at each connector receptacle.