S15/T15 Sonoma P/U 2WD V6-262 4.3L VIN W CPI (1994)
The ohmmeter is used to read resistance (ohms) or to check for opens or shorts in a circuit or component. There are both analog-type and digital-type
ohmmeters.
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An analog ohmmeter shows the actual resistance on a scale by the movement of a needle.
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On a digital ohmmeter, the resistance measured is converted inside the meter to a numerical output which is shown on a display panel.
Ohmmeters use a small battery to supply the voltage and current which flow through the circuit being tested. The current flows through the circuit,
positions the needle on analog-type ohmmeters or converts to a digital readout on digital-type ohmmeters.
Although there are several different styles of analog ohmmeters, all usually have the following features in addition to the meter movement:
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A range selector switch which permits the selection of different ranges of resistance.
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A set adjust control which allows the meter to be set at zero for accurate measurements.
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Some model ohmmeters also have a built-in feature that allows the ohmmeter to be used as a self-powered test lamp.
Digital meters do not have to be zeroed. They have various ranges just like the analog meters.
NOTE: Like a self-powered test lamp, the ohmmeter can only be used on circuits where voltage has been removed. It is designed to be operated on its
own voltage and current levels for the meter to make resistance measurements. The 12-volt electrical system voltage in the vehicles circuits could
damage the meter.
Electrical circuits can be checked for opens using basically the same procedure as previously described for the self-powered test lamp. The circuit must
be separated from all voltage sources. The ohmmeter is connected across the two open ends of the circuit to be checked. A high reading (infinity) is an
indication of an open circuit. A low reading (near zero) is an indication of a continuous circuit.
Checks for short circuits are made in a similar manner to that used for open circuits, except that the circuit being checked must be isolated from both
voltage and normal ground.
Connecting the ohmmeter between an isolated circuit and a good ground point allows checking the circuit for shorts to ground.
A short to ground in the circuit is indicated on the meter by a near zero reading. A good circuit (no short to ground) shows up as infinity (very high
resistance) indicated on the meter.
To measure the resistance of a component or a circuit, the component or circuit must be isolated from all other components (or circuits). The ohmmeter
leads are then placed across the component or circuit and the resistance is read on the ohmmeter.
Voltmeter
Voltmeter
