FREE Online ASE Course: BAR Diagnostic Repair Course – Voltage Drop
The most essential check you can do on an automotive electrical circuit is a voltage drop followed by checking the available voltage or should I say the potential voltage in a circuit
A voltage drop is a very good way to find extra resistance before or after a load. Remember just checking for open circuit voltage does not find resistance, and resistance will cut down current in a circuit.
High resistance or unwanted resistance will rob the intended load of the required voltage drop, because the voltage is now share across another or unintended resistance.
When this happens you will have components not functioning normally.
A voltmeter is checking the difference in electrical pressure between the red and black leads of the voltmeter.
By using the meter correctly, the technician can find high resistance, open circuits and shorts.
Remember the voltmeter is connected in parallel to a circuit, a voltmeter is not connected in series.
A good voltmeter should have an internal resistance or impedance at least 10 megohms, 20 megohms is better. The reason why: when the meter is connected to the circuit very little current flows through the meter so not to interfere with the operation the circuit.
The voltage in an electrical circuit a load uses is called a Voltage-Drop. Every circuit has to drop voltage across a load for that load device to work.
Every load is design with a certain amount of resistance.
However, when you have unwanted resistance, which can interfere with a circuit’s operation, resistance will lower the current and voltage to a component within a circuit.
Excessive Voltage drops is usually cause by high resistance, loose connections, frayed wires, and corrosion.
You can locate the unwanted resistance within a circuit by doing a voltage drop, but remember to perform a voltage drop, current must be flowing in a circuit.
Voltage drops can are perform by probing both sides of a circuit, with a voltmeter. The positive lead of the meter to the most positive side of the circuit. That is usually close to the power source and the negative lead to the least positive source, closest to the ground circuit.
A voltage drop is used to check for unwanted resistance in a circuit either on the power side or the ground side of the circuit.
High resistance on either side of the load, the load or component does not function normally.
Remember to perform a voltage drop, current most be flowing in that circuit.
Basic Circuit Description:
Watch this BAR Specified Repair License Video:
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