Caution – C.E. Niehoff & Co. C722 & C724 Troubleshooting Guides User Manual
Page 5
Page 5
TG71A
Section C: Advanced Troubleshooting
(CONT’D)
Yes
No
Alternator is defective.
With engine off, unplug alternator-to-regulator harness. Connect DMM red lead to pin A on harness plug.
Connect black lead to pin F on same plug. Does resistance measure about 1.2 (± 0.2) ohms?
Chart 1 –
C722 and C724 – No Alternator Output – Test OVCO Circuit
Yes
No
Connect DMM red lead to pin A on alternator-to-
regulator harness plug. Connect black lead to
alternator B– terminal. Does continuity exist?
Regulator is defective.
Alternator is defective.
Chart 2 –
C722 and C724 – No Output
Alternator is defective.
Figure 4 – Alternator-to-Regulator Harness Plug
PIN CONNECTIONS
Pin A
F–
Pin B
Phase
Pin C
B–
Pin D
B+
Pin E
D+
Pin
F
F+
Connect B+ battery cable to alternator. Turn on battery
switch. Install a jumper from pin F in harness plug to B+
terminal on alternator. Momentarily (1 sec.) jumper pin A
in harness plug to alternator B– terminal. Touch shaft with
steel tool to detect significant magnetism. Is shaft magnetized?
Yes
No
Go to Chart 3, page 6.
Turn off battery switch. Disconnect B+ cable from alternator.
Set DMM to diode test. Connect black lead of DMM to pin E in
harness plug. Connect red lead to B+ terminal on alternator.
DMM should read OL. Reverse leads. DMM should also read OL.
Yes
No
Alternator is defective.
Regulator is defective.
This step must be performed to obtain
a valid diagnosis of the alternator operation.
Install a jumper from B+ terminal on alternator to IGN or E terminal on regulator. Momentarily (1 sec.)
jumper IGN or E terminal on regulator to D+ terminal on regulator. Touch shaft with steel tool to detect
significant magnetism. Is shaft magnetized?
Yes
No
Retest alternator.
With engine running, does battery voltage exist at alternator B+ terminal and regulator IGN or E terminal?
Yes
No
Repair vehicle harness circuit to IGN or E terminal on
regulator or B+ terminal on alternator.
CAUTION
With key off, engine off: Disconnect both jumper wires. Unplug alternator-to-regulator harness. Connect
DMM on DC volt scale across pins C and D in harness plug. Does battery voltage exist?
Yes
No
When conducting this step, ensure that the probes do not touch other pins,
as an arc may damage the wiring in the harness.
CAUTION