Vehicle Test Meter (VTM)

TM 9-2320-279 -20-1

Instructions (Cent)

SIMPLIFIED TEST EQUIPMENT FOR INTERNAL COMBUSTION ENGINES

2-16.

INTRODUCTION

a specific malfunction is known,

(3) Isolation and Correction of Specific Malfunctions.

2-10

unnecessary testing can be avoided by going directly to the appropriate test, or tests, indexed in

or 2-11. The relationship of the GO and NO-GO tests are shown in Figure 2-18. Note that GO1 test, VTM

connections and checkout, must be performed before conducting any other tests.

is a testing system that performs tests and

Operation

Description.

measures standard voltage, current, resistance,

measurements on internal combustion engines.

pressure, and temperature. Special tests, such as compression balance tests and starter system evaluations

Standard equipment functions including vacuum pressure gage, low-current

are performed by

set.

is portable and operates on either 12 or

tester, and multimeter are features of the

system consists of a Vehicle

Meter

24-volt vehicle batteries or equivalent power source. The

four electrical cables, a transit case, and technical manual (fig. 2-19).

(VTM), a Transducer Kit

d. Vehicle Test Meter

Description. The VTM is a tool for the mechanic to test vehicle electrical and mechanical

components. Readings are either pass/fail indications or digital displays in units familiar to the mechanic

(psi, rpm, volts, ohms, amps, etc.).

The VTM interfaces with the vehicle by either a permanently mounted

or directly with a transducer from the Transducer Kit

The

Diagnostic Connector Assembly

DCA provides accessibility to the most frequently needed test points. This use of the VTM is called the

DCA mode of operation. The VTM also interfaces with transducers from the transducer kit for testing or

troubleshooting. This use of the VTM is called the TK mode of operation. Additional tests not in the DCA

mode can also be done in the Transducer Kit (TK) mode. These involve manually probing and/or connecting

transducers to appropriate test points.

Operating power for the VTM is drawn from the vehicle batteries or some equivalent

battery source. Power is routed to the VTM through the diagnostic connector in the DCA mode, or through

cable clamps connected to the battery in the TK mode.

e. Transducer Kit Components. The Transducer Kit contains a pulse tachometer transducer, a

pressure and a vacuum transducer along with the necessary adapters (bushings, plugs, tees, etc.). Also

included in the kit is a current probe for measuring current and a test probe cable for measuring voltage

and resistance. The transducers and adapters are non-repairable. The cables are non-repairable at

organizational maintenance level.

Controls and Readout Display. The controls and readout display

f. Vehicle Test Meter

on the VTM are illustrated in Figure 2-20. The following paragraphs describe how the controls are used,

and how the display functions.

(1) Power Switch (PUSH ON/PULL OFF). The power switch controls DC power to the VTM. The VTM

can operate from a 12-volt or 24-volt battery system. When the power switch is pushed in (PUSH ON), the

shut the VTM off, pull out the power switch (PULL OFF). The power switch contains

VTM power is on.

a 4-amp circuit breaker. The power switch will pop out automatically if something is wrong which causes

the VTM to use more power than it should. If the switch pops, check the hookup carefully and try again

Maintenance.

before sending the VTM to

2-272