C.E. Niehoff & Co. Diode Heat Sink Assy Replacement Instructions - Manual

II113B Page 1 of 1
Diode/Heat Sink Assembly
Replacement Instructions
C. E. Niehoff & Co. • 2021 Lee Street • Evanston, IL 60202 Tech Services Hotline 800-643-4633
To replace any of three diode module/
heat sink assemblies:
1. Remove drive end cover plate and save hardware for
reassembly.
2. Remove and save the hardware attaching the defec-
tive diode module/heat sink assembly.
3. Disconnect only enough wiring attached to defective
diode/heat sink assembly to facilitate replacement.
4. Remove defective Diode/heat sink assembly. Clean
away debris or corrosion from housing surfaces
before installing new assembly.
5. Install new diode/heat sink assembly in proper
location. See Figure 1. Torque heat sink mounting
screws to 11.3–13.5 Nm/100–120 lb. in.
6. Reconnect wiring removed in step 2:
a. Phase lead to each diode module as shown in
Figure 1. Torque to 4 Nm/35 lb. in.
Phase lead attaches here under spacer;
brown harness lead attaches on top of spacer

Figure 1 – Diode/Heat Sink Assemblies
A8-122/A8-125/N7354
Diode/Heat Sink Assembly

B+ stud — B+ leads attached
to modules (3 places)

b. To B+ stud and torque screw to 28-29 Nm/
21- 22 lb. ft. From B+ wire assembly to diode
module and torque screws to 4 Nm/35 lb. in.
c. From regulator harness to module screws and
torque screws to 4 Nm/35 lb. in.
d. From green ground wire to heat sink and torque
screw to 11.3–13.5 Nm/100–120 lb. in.
7. Coat electrical terminals with Dow Corning® 1–2577
Low VOC RTV coating or equivalent. Do not use
coating containing acetic acid (vinegar smell) on
electrical components.
8. Using DMM (digital multimeter) set on diode test,
connect red lead to B+ teminal on alternator and
connect black lead to B– terminal on alternator.
Meter should read OL (blocking). Reverse leads,
meter should read less than 0.8 V (flow). If meter
reads zero in either direction, recheck wiring
connections and diode orientation.
9. Reattach drive end cover plate and torque hardware
to 5.1 Nm/45 lb. in.
A8-123/A8-126/N7352
Diode/Heat Sink Assembly

A8-123/A8-126/N7352
Diode/Heat Sink Assembly


Phase lead attaches here

Phase lead attaches here 
Regulator harness