Actron CP7677 Operations Instructions download pdf (Page 11)

11

Fig. 13

7. Switch RED and BLACK test leads

and repeat Step 6.

8. Test Results

If the display showed:

• A voltage drop of 0 volts in both

directions, then the diode is shorted

and needs to be replaced.

• A “1” appears in both directions,

then the diode is an open circuit

and needs to be replaced.

• The diode is good if the display

reads around 0.5V–0.7V in one di-

rection and a “1” appears in the

other direction indicating the multi-

meter is overranged.

Measuring Engine RPM

RPM refers to revolutions per minute.

When using this function you must multi-

ply the display reading by 10 to get actual

RPM. If display reads 200 and the multim-

eter is set to 6 cylinder RPM, the actual

engine RPM is 10 times 200 or 2000 RPM.

To measure Engine RPM (see Fig. 14):

Testing Diodes

A diode is an electrical component that

allows current to only flow in one direc-

tion. When a positive voltage, generally

greater than 0.7V, is applied to the an-

ode of a diode, the diode will turn on and

allow current to flow. If this same volt-

age is applied to the cathode, the diode

would remain off and no current would

flow. Therefore, in order to test a diode,

you must check it in both directions (i.e.

anode-to-cathode, and cathode-to-an-

ode). Diodes are typically found in alter-

nators on automobiles.

Performing Diode Test (see Fig. 13):

Typical

Ignition

Coil

Ground

Black

Red

Fig. 14

Anode

Cathode

Black

Red

1. Insert BLACK test lead into COM

test lead jack.

2. Insert RED test lead into

test lead jack.

3. Connect RED test lead to TACH

(RPM) signal wire.

• If vehicle is DIS (Distributorless

Ignition System), then connect RED

test lead to the TACH signal wire

going from the DIS module to the

vehicle engine computer. (refer to

vehicle service manual for location

of this wire)

• For all vehicles with distributors,

1. Insert BLACK test lead into COM

test lead jack.

2. Insert RED test lead into

test lead jack.

3. Turn multimeter rotary switch to

function.

4. Touch RED and BLACK test leads

together to test continuity.

Check display – should reset to 0.00.

5. Disconnect one end of diode from

circuit.

Diode must be totally isolated from

circuit in order to test its functional-

ity.

6. Connect RED and BLACK test

leads across diode and view dis-

play.

Display will show one of three things:

• A typical voltage drop of around

0.7V.

• A voltage drop of 0 volts.

• A “1” will appear indicating the mul-

timeter is overranged.

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