General Relay Troubleshooting Procedures

TM 9-2320-364-20-1

2-11. TROUBLESHOOTING INSTRUCTIONS (CONT).

(3)

Voltage measurements. The PLS truck is equipped with both 12 vdc and 24 vdc circuits.

Troubleshooting procedures will reference 12 vdc and 24 vdc measurements, however these values can

vary. When the batteries are fully charged, 12.6 vdc can be measured on an open 12 volt circuit and 14.5

vdc can be measured when the engine is running at 1000 rpm. When the batteries are fully charged, 25.2

vdc can be measured on an open 24 volt circuit and 29 vdc can be measured when the engine is running

at 1000 rpm.

(a)

Connect the red test lead to the volt-ohm input connector and the black lead to the COM input on

the meter. If a DC-AC switch is present, make sure it is set to the DC position.

(b)

Set the function/range switch to the desired volts position. If the magnitude of the voltage is not

known, set the switch to a range which will be able to read most voltages seen on the truck

(typically, a 200V range will do). Then reduce the range until a satisfactory reading is obtained.

(c)

Connect the test leads to the circuit being measured. In the DDEC II diagnostic procedures, voltage

measurements are always given as being taken at pins, sockets, battery (+) or ground. Following

the voltage measurement point, the color test lead tube used is given in parenthesis (red is volt-ohm

connection and black is the COM connection).

f. General Relay Troubleshooting Procedures. The following general relay troubleshooting procedures

apply to all PLS relays.

NOTE

Configuration data covering each relay is listed in Table 2-14.

(1)

Pull relay out of socket just enough for the relay terminals to make contact with receptacle terminals.

Leave about 1/4 to 3/8 in. (6.35 to 9.53 mm) space between the relay and relay socket to insert a

multimeter lead and make contact with the terminal listed in the troubleshooting test.

(2)

Perform truck operation that will actuate the relay in question.

g. General Wire Test Procedures. PLS troubleshooting isolates problems down to the components that

could cause a specific failure. When all of the components in a circuit are tested without isolating a fault, the

wires are the only other components that could be suspected of being damaged. Each wire that must be tested

may pass through two or more connectors. The following procedures provide general instructions for testing

electrical wires. These procedures will either attempt to measure a voltage at the working end of a circuit or

continuity from the power end of a specific wire to the working end. Before either of these tests are performed,

all connectors in the circuit must be checked for looseness.

Use proper sized test leads and ensure care is used when checking for resistance,

continuity or voltage at connectors or damage to equipment may result.

(1)

Wire voltage drop test.

(a)

Disconnect connector from the component (light, relay, motor, etc.) at the working end of the

circuit.

(b)

Check connector terminal(s) for damage; repair or replace connector as necessary.

(c)

Setup truck conditions that will create voltage at the working end of the wire.

2-122