250V MAX
15A MAX
FUSED
COM
DC
15A
AUTO POWER OFF
CP7678
®
OFF
200
20
2
DC V
200
m
20M
200
K
20K
2K
200
8CYL
6CYL
TACH
X10
5CYL
4CYL
8CYL
6CYL
5CYL
4CYL
DWELL
DUTY
CYCLE
%
OHMS
°
15
A
250V MAX
15A MAX
FUSED
COM
DC
15A
AUTO POWER OFF
CP7678
®
OFF
200
20
2
DC V
200
m
20M
200
K
20K
2K
200
8CYL
6CYL
TACH
X10
5CYL
4CYL
8CYL
6CYL
5CYL
4CYL
DWELL
DUTY
CYCLE
%
OHMS
°
15
A
12
Measuring Dwell
Dwell measuring was extremely important on
breaker point ignition systems of the past. It
referred to the length of time, in degrees, that
the breaker points remained closed, while the
camshaft was rotating. Today’s vehicles use
electronic ignition and dwell is no longer ad-
justable. Another application for dwell is in
testing the mixture control solenoid on GM
feedback carburetors.
5. Turn multimeter rotary switch to cor-
rect DWELL CYLINDER position.
6. View reading on display.
Measuring Duty Cycle
Duty Cycle refers to the percentage of time a
signal is “ON” verses “OFF”. A signal that is
“ON” half the time has a 50% Duty Cycle. Duty
Cycle is useful for checking solenoids, relays,
switches, fuel injectors and any other compo-
nent that is switched “ON” and “OFF”.
To measure Dwell (see Fig. 13):
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 DWELL signal
wire.
• If measuring DWELL on breaker point
ignition systems, connect RED test lead
to negative side of primary ignition coil.
(refer to vehicle service manual for loca-
tion of ignition coil)
• If measuring DWELL on GM mixture con-
trol solenoids, connect RED test lead to
ground side or computer driven side of
solenoid. (refer to vehicle service manual
for solenoid location)
• If measuring DWELL on any arbitrary
ON/OFF device, connect RED test lead
to side of device that is being switched
ON/OFF.
4. Connect BLACK test lead to a good
vehicle ground.
Fig. 13
Fig. 14
To measure Duty Cycle (see Fig. 14):
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 ON/OFF
switching side of device.
4. Connect BLACK test lead to a good
vehicle ground.
5. Turn multimeter rotary switch to DUTY
CYCLE position.
6. View reading on display.
Ground
Black
Red
Typical
Ignition
Coil
Black
Ground
Red
On/Off
Switching
Side
Power
Side
Solenoid
