Electrical Environment: Ac Vs. Dc - Cub Cadet RZT-S Professional Shop Manual

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• Low Voltage: Many electronic devices simply stop working if system voltage falls below a given thresh-
old. If a 12 volt system is run at 11 volts with a failing alternator, electronic controls may stop working.
• Bad Grounds: Bad grounds can reduce the effective system voltage, create resistance and heat, and
send false signals. This is the single most common breeding ground of electronic gremlins.
• Heat and Vibration: Heat and vibration are hard on most mechanical devices. The same is true of elec-
tronics.
• Moisture: Moisture causes a nasty combination of corrosion and shorts. Corroded connections and wires
create resistance that results in low voltage and grounding issues. Many electronic components are "pot-
ted" or encased in a sealant that protects them from moisture. They are still vulnerable to bad inputs
caused by corroded external connections and damaged switches.
• Improper Tools: Some test lights can over load electronic circuits.

Electrical environment: AC Vs. DC

Most modern outdoor power equipment that has an electrical system complex enough to require diagnosis will
be equipped with an alternator that produces alternating current (AC). In most systems, this current is immediately
rectified to direct current (DC), and regulated to a nominal 12 Volts. The presence of AC is very limited. The primary
concern of this section is 12 Volt DC systems, though much of the theory and techniques apply equally well to other
DC systems.
1. Voltage: Pressure
• Voltage is the "pressure" that electricity has. It is the amount of force pushing electrons through a circuit.
• The unit of measurement for this pressure is volts.
• The capital letter "V" is used to represent volts.
• Most (not all) outdoor power equipment operates on a nominal 12 volts. In practice, system voltage may
run as high as 13.5V or 14V.
2. Current: Flow
• Current is the "flow" of electricity. It is the amount of electrons flowing in the circuit.
• The flow of current is measured in Amperes or Amps for short.
• The capital letter "I" (Intensity of current flow) is used to represent Amps.
3. Ohms: Resistance
• Resistance is the opposition to current flow. It is a restriction that slows down the flow of current.
• Resistance is measured in Ohm's.
• The greek letter omega "
• Resistance creates heat. A circuit with too much electrical load or too much resistance for the load placed
on it will get hot.
Ω",
or the letter "R" for Resistance is used to represent Ohm's.
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Electrical System
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