SECTION 6 - TROUBLESHOOTING
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NOTE:
For aid in troubleshooting electrical problem, refer to Figure 6-8. for an ELECTRICAL DIAGRAM of the various circuits. Also for a picto
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rial overview of the connected components, See Figure 6-6. “Pictorial Overview of the MVL/MSP Electrical System”.
6.5 MULTIMETER BASICS
A wide variety of multi-meters or Volt Ohm Meters (VOM) can be used for troubleshooting your equipment. A digital meter with rea
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sonable accuracy (within 7%) is recommended for the measurements in these procedures. This section shows diagrams of a common,
digital VOM configured for several different circuit measurements. Instructions for your VOM may vary. Please consult the meter oper
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ator’s manual for more information.
Grounding
“Grounding the meter” means to take the black lead (which is connected to the COM (common) or negative port) and touch it to a
good path to the negative side of the voltage source.
Back-Probing
To “back-probe” means to take the measurement by accessing a connector’s contact on the same side as the wires, the back of the
connector. Readings can be done while maintaining circuit continuity this way. If the connector is the sealed type, great care must be
taken to avoid damaging the seal around the wire. It is best to use probes or probe tips specifically designed for this technique, espe
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cially on sealed connectors. Whenever possible insert probes into the side of the connector such that the test also checks both termi
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nals of the connection. It is possible to inspect a connection within a closed connector by back-probing both sides of a connector
terminal and measuring resistance. Do this after giving each wire a gentle pull to ensure the wires are still attached to the contact and
contacts are seated in the connector.
Min/Max
Use of the “Min/Max” recording feature of some meters can help when taking measurements of intermittent conditions while alone.
For example, you can read the voltage applied to a solenoid when it is only operational while a switch, far from the solenoid and
meter, is held down.
Polarity
Finding a negative voltage or current reading when expecting a positive reading frequently means the leads are reversed. Check what
reading is expected, the location of the signal and that the leads are connected to the device under test correctly. Also check that the
lead on the “COM” port goes to the ground or negative side of the signal and the lead on the other port goes to the positive side of
the signal.
Scale
M = Mega = 1,000,000 * (Displayed Number)
k = kilo = 1,000 * (Displayed Number)
m = milli = (Displayed Number) / 1,000
µ = micro = (Displayed Number) / 1,000,000
Example: 1.2 k
= 1200
Example: 50 mA = 0.05 A
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