Pinpoints Tests; Dead Battery/No Generator Output; Check For Key Off Drain - Ford LRG-423 Service Manual

03-74
Auxiliary Systems 03-74
GENERATOR DIAGNOSIS AND TESTING (Continued)
Pinpoint Tests
All voltage measurements are referenced to the
negative (-) battery post unless otherwise specified.
Do not make jumper connections except as directed.
Improper connections may damage the voltage
regulator or fuses/fuse links.
All " key ON" measurements are made with the engine
not running unless directed to " start engine" .
PINPOINTTEST A: DEAD BATTERY/NO GENERATOR OUTPUT
TEST STEP
RESULT b ACTION TO TAKE
Al
CHECK FOR KEY-OFF DRAIN
l
Turn key to OFF position.
Yes ) GO to A2.
l
Turn off all accessories. No b Check to ensure that the key
l
Connect an ammeter or test lamp between the
switch is functioning
negative (-) battery cable and the negative battery
properly, and that all lights
post.
and accessories are " off"
l
Is current drain less than 100 mA (or test lamp
with the key switch in the
off)?
" off" position.
A2 1 CHECK FOR OPEN B+ CIRCUIT
l
Measure voltage at B+ terminal on the back of the
Yes ) GO to A3.
generator, Circuit 38 (BWO).
l
Is voltage at B+ terminal equal to battery voltage?
No ) CHECK fuse link in Circuit
C
%
/
38,290, and 37 and
t
REPLACE if required. If OK,
REPAIR open in Circuits 38,
290, and 37.
A3
CHECK FOR OPEN A CIRCUIT
l
Measure voltage at test point A on the voltage
Yes
b GO to A4.
regulator.
l
Is voltage at test point A equal to battery voltage?
No b CHECK fuse or fuse link in
Circuit 36 and REPLACE if
required. If OK, REPAIR
open in Circuit 36 (Y/W).
A4
1 CHECK FOR OPEN FIELD CIRCUIT
l
Measure voltage at test point F on the voltage
Yes b GO to A5
regulator.
l
Is voltage -at test point F equal to battery voltage?
No ) GOtoAll.
A5 1 CHmFOR OPEN I CIRCUIT
l
Turn key to ON position.
Yes
b GO to A6.
l
Measure voltage at wiring harness I terminal, Circuit No
) REPAIR open or high
904 (LG/R).
resistance in Circuit 904
NOTE: Voltage regulator must be connected to wiring
(LG/R).
harness for this test.
l
Is voltage greater than 1 volt?
A6 CHECK VOLTAGE DROP IN A CIRCUIT
l
Measure voltage drop between test point A on the
Yes
) GO to A7.
voltage regulator and the positive (+) battery post.
l
Is voltage drop less than 0.25 volts?
No
b REPAIR excess voltage drop
in Circuit 36 (Y/w). CHECK
fuses or fuse link and
connectors in Circuit 36 and
SERVICE as required.
A7 CHECK FIELD TURN-ON
l
Measure voltage at test point F on the voltage
Yes b GO to AS.
regulator.
l
Is voltage at test point F less than 2 volts?
No
) GOtoAll.