Ammeter Diagnosis; Voltmeter Diagnosis; Fuel Gauge Diagnosis; Tachometer Diagnosis - Jeep J-10 Series 1982 Technical & Service Manual

IU ENGINE INSTRUMENTATION
(7) Test for short circuits between circuits. With
probe connected to applicable pin for circuit to be tested,
move other probe to all other pin terminals on cluster.
Ohmmeter should indicate infinite resistance between
circuits.
Ammeter Diagnosis
The accuracy of an ammeter may be determined by
comparing indications with those of a test ammeter of
known accuracy.
(1) Turn ignition switch off.
(2) Disconnect battery positive cable from terminal
on starter motor solenoid.
CAUTION: Test ammeter must be an actual ammeter,
not a voltmeter with a calibrated ammeter scale. Con
necting a voltmeter in series will destroy its internal
circuitry.
(3) Connect test ammeter in series between solenoid
terminal and disconnected cable.
(4) Turn ignition switch to On position. Do not start
engine. Turn headlamps on. Turn heater blower motor
to high speed.
(5) Compare current flow (amps) indication of test
ammeter with that of ammeter installed in vehicle.
(6) Turn headlamps and heater blower motor off.
Start engine and operate at high idle. Compare current
flow (amps) indication of test ammeter with that of
ammeter installed in vehicle.
(7) Replace ammeter if current flow (amps) in
dications of vehicle ammeter and test ammeter vary
more than calibration tolerance listed in Specifications.
Voltmeter Diagnosis
(1) Connect test voltmeter of known accuracy
across battery terminals.
(2) Turn ignition switch on.
(3) .Compare voltage indication of test voltmeter
with that of voltmeter installed in vehicle. Replace volt
meter if voltage indications vary more than calibration
tolerance listed in Specifications.
Fuel Gauge Diagnosis
Movement of the fuel in the tank can occur when
driving up or down hills, driving on rough surfaces or by
rapid acceleration or sudden braking. Erratic up and
down motion of the fuel gauge sending unit float may
temporarily cause the fuel gauge pointer to fluctuate
and indicate incorrectly. Ensure that all these possi
bilities are considered before suspecting an actual ab
normal condition in the fuel level indicating system.
Abnormal conditions all result from variations of four
basic malfunctions:
• pointer does not move,
• pointer moves but indicates a fuel level that does not
correspond with the actual fuel level,
• pointer moves to the top of the scale and remains
there,
• pointer pulsates.
Refer to DARS chart 1 for a systematic method of
locating the causes of these abnormal conditions. Charts
2 and 3 provide additional procedures that should be
used only as directed in chart 1.
Oil Pressure Gauge Diagnosis
An oil pressure gauge malfunction can result in any
one of the following conditions:
• pointer does not move,
• pointer moves but indicates an oil pressurethat does
not correspond with the actual oil pressure,
• pointer moves to the top of the scale and remains
there,
• pointer pulsates.
Refer to DARS chart 4 or 5 for a systematic method of
locating the causes of these abnormal conditions.
Calibration Test
If an oil pressure gauge is suspected of indicating
pressure that does not correspond with the actual oil
pressure, perform a calibration test before performing
electrical diagnosis procedures in DARS chart 4 (CJ) or 5
(Cherokee, Wagoneer and Truck).
(1) Remove oil pressure sending unit from cylinder
block. Install T-fitting in cylinder block. Connect send
ing unit to T-fitting.
(2) Connect oil pressure test gauge to T-fitting.
(3) Start engine. Compare pressure indicated on ve
hicle gauge with that on test gauge. Conduct comparison
at idle and at higher engine speeds. If both gauge in
dications are same (within 10 percent), vehicle gauge is
acceptable. If gauge is not within specification, perform
gauge test as outlined in DARS chart 4 or 5.
(4) After performing test, remove T-fitting, install
sending unit and inspect for oil leaks.
Tachometer Diagnosis
Test the accuracy of a tachometer by comparing with
rpm indications of a test tachometer of known accuracy.
A service (TACH) terminal is located on the ignition coil
connector for the test tachometer connection. Refer to
Chapter 1G—Ignition Systems. Tachometers are not ad
justable. Replace if defective.
NOTE: Some test tachometers may not be compatible
with the High Energy Ignition (HEI) System used with
four-cylinder engines. Consult the manufacturer of the
test tachometer ifproblems arise.