C.E. Niehoff & Co. C653/C653A/C625 Troubleshooting Guides - Manual (Page 10)

Page 10 TG13G
Section E: C653 w/A2-338 Advanced Troubleshooting
A2-338 Regulator
Description and Operation
A2-338 regulator is attached directly to the outside of
alternator. A9-4011 temperature sense lead may or may
not be used with this regulator. See below.
Main diagnostic feature of the regulator is a tricolored
LED next to the harness receptacle on regulator. LED
works like a voltmeter, measuring charging voltage. See
Table 3 for diagnostic features and LED explanations.
This regulator has OVCO (overvoltage cutout) that will
trip at vehicle electrical system voltage above 33 volts
that exists longer than 3 seconds. OVCO feature detects
high voltage and reacts by signaling field circuit to open.
This turns off alternator (LED is flashing RED). OVCO
circuit is reset when engine is restarted or when system
voltage drops below 26.5 V.
When the A9-4011 temperature sense lead is not in use,
the regulator will operate at 27.5 V.
When A9-4011 temperature sense lead is in use, the
lead senses the ambient temperature within the battery
box and regulator will adjust charge voltage based on
battery temperature—the higher the battery tempera-
ture, the lower the charge voltage.
LED COLOR STATUS
TABLE 3 – A2-338 Regulator Diagnostics
Alternator and regulator operating normally.
Regulator is in soft start mode. GREEN Solid
Flashing
Low system voltage — Electrical load exceeds
alternator rating at present rotor speed.
ACTION
No action required.
Wait 10 seconds until alternator achieves full
rotation.
When loads decrease or speed increases, LED
should be solid GREEN. If not, check drive belt
and charging system connections. AMBER Solid
High system voltage – May occur during
normal load switching. If solid more than 3 seconds, OVCO will trip,
disabling charging system. LED will flash RED.
Overvoltage condition. Attempt reset. System
diagnosis required. Go to Chart 5, page 11. RED Solid
Alternator fault — No output. Flashing
Flashing OVCO tripped.
Troubleshooting
Shut down vehicle and restart engine. If alternator
functions normally after restart, a “no output condition”
was normal response of voltage regulator to “high volt-
age” condition. Inspect condition of electrical system,
including loose battery cables, both positive and
negative. If battery disconnects from system, it could
cause “high voltage” condition in electrical system,
causing OVCO circuit to trip.
If you have reset alternator once, and electrical system
returns to normal charge voltage condition, there may
have been a one time, high voltage spike, causing OVCO
circuit to trip.
If OVCO circuit repeats cutout a second time in short
succession and shuts off alternator field circuit, try
third restart. If OVCO circuit repeats cutout, go to Chart
5, page 11.
Replace alternator.