C.E. Niehoff & Co. N1126-2 Instructions
N1 126-2 Alternator
N9700 Filter Replacement Kit and
Diode Module Test
Field Instructions
Disassembly:
1. Disconnect alternator-to-regulator harness plug at
regulator.
2. Remove and discard four screws from black cover
plate on control unit. Loosen cover to access wiring
underneath.
3. Label and disconnect three harness leads, red
(B+), green (B–), and brown (AC) from defective
filter.
4. Label three black phase leads from diode module at
filter.
5. Remove and discard six screws attaching filter to
diode module.
6. Uncouple gray connector on harness.
7. Remove and discard filter.
8. Test diode module per Table 1, page 2.
• If defective, see diode replacement on page 2.
• If not defective, follow directions below for
reassembly.
Assembly:
NOTE: Before reassembly, make sure all ring, power,
and diode terminals are cleaned with a wire brush to
remove any conformal coating and ensure a good electrical connection.
1. Put end of harness with ring terminal through hole
in cover from outside.
2. Mate two ends of gray connector.
3. Install phase leads, copper links, and spacer
washer between new filter and diode module using
new hardware. Leave fasteners loose.
4. Install screws in terminals E, A, and C. Leave
fasteners loose. See Figure 3 on page 2.
5. Using new hardware, install red harness lead
(B+) in terminal D. Install brown harness lead (AC)
in terminal B and green harness lead in terminal F.
6. Torque down all fasteners (4.6 Nm/40 lb. in.) taking
caution to ensure proper connection.
7. Replace black cover plate and torque fasteners to
2.3 Nm/20 lb. in.
8. Reconnect alternator-to-regulator harness plug at
regulator.
Screw
V
Washer
V
Filter
V
V
er terminal (phase lead,
Pow
copper link, or spacer washer)
V
Diode module
Use washer as spacer between fi lter and di-
ode module in this position only
Red
Filter
Green
V
V
V
V
V
V
V
V
V
Figure 1 – Diode Module Stacking Order
Black cover plate
V
Brown
Three phase leads
Page 1 of 2
Figure 2 – Replacing Filter and Black Cover Plate on N1126-2 Alternator
II0120A
Diode module tests:
F
C
Figure 3 – Diode Module Terminal Designations
D
E
B
A
TABLE 1 Diode Module Tests
TABLE C– 4 C704 Diode Module Tests
REMOVE PHASE LEADS. USE DIODE TEST SCALE ON DMM.
REPEAT TESTS FOR EACH MODULE. SEE FIGURE C–11.
TEST
NO.
1
2
3
4
5
6
7
8
9
10
11
12
CONNECTION
USE DIODE TEST SCALE ON DMM.
SEE FIGURE 3.
METER
(+) LEAD
Terminal A
Terminal A
Terminal B
Terminal B
Terminal C
Terminal C
Terminal D
Terminals E & F
Terminal D
Terminals E & F
Termi n a l D
Terminals E & F
METER
(–) LEAD
CONNECTION
Terminal D
Terminals E & F
Terminal D
Terminals E & F
Terminal D
Terminals E & F
Terminal A
Terminal A
Terminal B
Terminal B
Terminal C
Terminal C
TESTED
CIRCUIT
(+) side diode
(–) side diode
(+) side diode
(–) side diode
(+) side diode
(–) side diode
(+) side diode
(–) side diode
(+) side diode
(–) side diode
(+) side diode
(–) side diode
EXPECTED
READING
<1.0 volts
(fl ow)
OL (blocking)
<1.0 volts
(fl ow)
OL (blocking)
<1.0 volts
(fl ow)
OL (blocking)
OL (blocking)
<1.0 volts
(fl ow)
OL (blocking)
<1.0 volts
(fl ow)
OL (blocking)
<1.0 volts
(fl ow)
To replace diode module:
1. Reference disassembly steps on page 1.
2. Remove and discard hardware and defective diode
module.
3. Clean housing surface to remove old heatsink
compound. Surface must be clean and flat before
applying new heatsink compound.
4. Apply a layer of heat sink compound, such as GC/
Waldon HSC # 10-8109 zinc oxide filled silicone or
its equivalent on the back of the new diode module
between the module and housing surface.
5. Install new diode module in orientation shown in
Figure 3. Stack mounting hardware on mounting
studs: nut, disc spring washer, flat washer. Torque
nuts to 12.5 Nm/9.2 lb. ft.
6. After diode module is secured in place, reference
reassembly instructions on page 1.
C. E. Niehoff & Co. • 2021 Lee Street • Evanston, IL 60202 Tech Services Hotline 800-643-4633
Page 2 of 2
II0120A
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