Nautilus Be Strong Commercial R916, Service Manual

Page: 30 / 68

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Alternator Testing
To minimize the complexity of the flowchart, this section will best be described in terms of system theory.
The colored connections to the alternator are as follows:
White-B+ — Alternator output voltage
Brown-Field — Alternator Control Current
Black-Ground — Alternator return
Prior to proceeding with tests below, perform continuity checks on the alternator cable, and confirm cable is securely
fastened to the alternator and the 27451 PCB.
For workouts that require levels of less than 50W resistance to the user, clinical mode must be used. In this condition,
the console is powered by an external power supply, and the alternator is not powered unless the user decides to
achieve levels of 50W or more.
If the bike’s speed is 40 RPM or greater, and assuming clinical mode is not desired, the system can subject the user
to a workout that is self-generating. Under self-generating conditions, the alternator is on; it is powering itself, the
console, and providing charge to the battery.
Prior to entering workout information, it is desired to have the user subjected to minimal resistance, and the console
is powered by the battery. Once the console knows all the user’s desired information, it turns on the alternator. The
alternator is turned on by a logic low on pin 2 of J5 of the 27451 PCB. This signal is also accessible on the 27451’s TP11.
Once the alternator is powered, the user sees an increase in resistance due to the alternator’s internal magnetic fields.
The 27451 PCB maintains a regulated voltage on the alternator’s B+ by varying the amount of current sourced into the
alternator’s field. B+ is sensed by the 27451, and the field current is altered until the alternator is at the desired voltage.
As the RPM increases, the alternator’s efficiency increases, and less field current is required.
Depending on the desired resistance level, the console can control the alternator’s output voltage by controlling the
logic level of pin 7 of J5 on the 27451 PCB. A logic low on pin 7 tells the 27451 to control at 7.8V or a logic high sets
9.8V.
If the alternator is not powering on, first confirm the bike is cranked at ~50 RPM, and that pin 2 of J5 (TP 11) is NOT
high. If it is, and a workout has been entered, suspect the console. If pin 2 of J5 is low, measure the alternator’s field
voltage. Without B+ the 27451 will attempt to force full current into the field, and in this condition it will be limited by
its input voltage, or the battery in this case. Therefore, if 5V or more is measured on the field with no B+, either B+ is
shorted or the alternator is defective. Before replacing the alternator, disconnect the B+ wires from the alternator’s
B+ terminal and see if an output voltage exists. If voltage is now present, which could easily exceed 30V in an uncon-
trolled state, the 27451 PCB is probably defective. With no load on B+, 5V or more field current, adequate RPM and no
B+, replace the alternator.
If no field voltage is detected, disconnect the B+ connections on the alternator, along with the field wire. Measure
the field resistance to alternator ground, which should be approximately 4 ohms which is a typical value of Prestolite
units. If the field resistance is way less than this or shorted, replace the alternator. If the field measures ~4 ohms, take
a jumper wire, and make a connection from the positive battery terminal to the alternator’s field tab. If the voltage now
jumps up to a level of 20 to 30V the alternator is good, and the 27451 needs replacing.
If the B+ voltage is sporadic first look for loose connections. This type of problem could be caused by a defective
alternator or 27451. If a known-good 27451 unit is available it will be the easiest component to replace. If the problem
goes away, confirm the other PCB still causes sporadic behavior, and the problem was not in fact a loose connection.