TM 5-5420-227-24
c. Vehicle Test Meter.
(l) General. The VTM provides a method for the technician to test vehicle electrical components, Readings are either
pass/fail indications or digital displays in units such as volts. Operating power for the VTM is drawn from the
vehicle batteries or some equivalent battery source.
(2) Controls and Indicators. The controls and readout display on the VTM are illustrated on page 2-38.
(a) Power Switch (PUSH ON/PULL OFF). VTM power is on when the power switch is pushed in and off
when pulled out. The power switch contains a 4-amp circuit breaker and will pop out automatically if
something is wrong which causes the VTM to use more power than it should. If the switch pops, check
your hookup carefully and try again before turning in the VTM to support maintenance.
(b) Test Select Switches, The TEST SELECT switches are used to select the actual test to be performed. There
are ten positions on each switch numbered O through 9. The number dialed into these switches is read by the
VTM when you press the TEST button.
(c) Test Button. Pressing and releasing the TEST button causes the test measurement to begin. Observe the
measured value on the readout display. The TEST button must be pressed and immediately released, unless
instructions in the test being performed state otherwise.
(d) Readout Display, The readout display will show different types of readouts during testing up to a maximum
of 4-characters (for example .8.8 .8.8). The types of readouts you will see are summarized as follows:
1. Status Readout. A status readout keeps the technician informed of what is happening. The status readout
displays are described in page 2-40.
2. Prompting Message. A prompting message is a technician action message. Prompting messages are
described in page 2-40.
3. Numerical Readout. A numerical readout is the measured value in units of the measurement being made.
For example, if you are measuring 0-45 volts dc, 24.2 is volts dc.
4. Error Readout. There are 5 different error readouts used with this vehicle. All error readouts
start with E. All error messages must be corrected before continuing testing. Error messages are
listed in page 2-41.
5. Confidence Error Readouts. C004 is a typical error readout resulting from the detection of a fault y VTM
during confidence test.
d. Cable Assemblies. Cable assemblies are referred to by the cable number and by a name which describes how the cable is
used. For example power cable W5, test probe cable W2. If you experience any difficulty during testing and suspect a
cable is bad, refer to TM9-4910-571-12 & P for checking cable continuity.
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