Urrea UD88 User's Manual And Warranty Information page 76

E N G L I S H
- Black lead in COM jack.
- Red lead in VΩRPM CAP jack.
Connect:
- Black test probe to the negative (cathode) side of
the diode pack.
- Red test probe to the positive (anode) side of the
diode pack.
If neither diode is shorted, about 0.8V should be
displayed.
If one diode is shorted, about 0.4V should be displayed.
If wire is open, both diodes are open or the voltage
drop is above 3V, "
"A Diode Pack in the Alternator contains 2 Diodes in Series"
Ignition Systems Tests
Since the Meter can measure from tenths of an Ohm up
to 40 million Ohms, this makes it very useful for testing
the resistance in most ignition system components. If
you suspect bad ignition wires, you can test resistance
of the wire while moving, twisting and bending the
wire. The resistance values will typically be around
10KΩ per foot. You can also check the resistance of
the ignition coil's primary and secondary windings, if
you suspect a problem with the ignition coil, you will
76
" should be displayed.
need to do this test, first, when the coil is hot, and
again when it is cold.
You should also measure from the coil's case to each
connector and between the primary and secondary
windings to ensure they are not shorted together. The
primary windings should have a very low resistance,
typically from a few tenths of an Ohm to a few Ohms;
the secondary windings have a much higher resistance
typically in the 10k Ohm range.
To get the actual figures for a specific coil, check the
manufacturer's specifications.
WARNING: ALWAYS DISCONNECT THE IGNITION COIL
FROM THE IGNITION SYSTEM BEFORE TESTING TO AVOID
AN ELECTRICAL SHOCK.
1. Spark Plug Wire (Secondary Ignition Wire)
Resistance Test
Spark plug wires should be checked if your oscilloscope
indicates that there may be a problem or if they are
more than two years old. You should be careful when
pulling the spark plug boot from the insulator as
bonding may have occurred.
If you suspect from a bad wire, test its resistance while
gently twisting and bending the spark plug wire. If
the resistance value changes while moving, twisting
or bending the wire and you are confident you have a
good connection, then replace the wire.
This test checks for high resistance or open circuits in
the secondary ignition wires (spark plug wires).
To measure the wire resistance:
- Set the rotary switch to resistance (Ω).
Insert:
- Black lead into COM jack.
- Red lead into VΩRPM CAP jack.
Connect:
• The test probes to opposite ends of the spark plug
wire.