Speed Control Servo; Stop Lamp Switch; Vacuum Supply Test - Dodge ram truck 3500 1996 Service Manual

8H - 8 VEHICLE SPEED C O l T i O L SYSTEM
BR
D I A G N O S I S A N D T E S T I N G (Continued)
(1) Disconnect negative battery cable. Wait 2 min­
utes for airbag system capacitor to discharge.
(2) Remove speed control switch module from
steering wheel. Refer to the removal/installation sec­
tion for procedures.
(3) Check speed control switch module continuity
as shown in chart (Fig. 1). I f OK, reinstall switch. I f
not OK, replace switch module assembly. The individ­
ual switches and the indicator lamp can not be ser­
viced separately.
REAR VIEW OF SWITCH
o o o
PIN
1
PIN 2
n i
, fl
PIN
3
SWITCH
POSITION
R E S I S T A N C E
B E T W E E N
PINS 2 AND 3
R E S I S T A N C E
B E T W E E N
PINS 1 AND 2
NO S W I T C H E S
D E P R E S S E D
OPEN
CIRCUIT
806 ohms
+/- 8 ohms
ON
909 ohms
+/- 9 ohms
R E S U M E / A C C E L
15,400 ohms
+/-154 ohms
S E T / C O A S T
6650 ohms
+/- 66 ohms
80468d39
Fig. 1 Speed Control Switch Continuity
STOP LAMP SWITCH
For continuity checks and switch adjustment, refer
to Group 5, Brakes.
VACUUM SUPPLY TEST
(1) Gain access to vacuum reservoir. Refer to
Removal/Installation section for procedures.
(2) Disconnect vacuum hose at the servo and
install a vacuum gauge into the disconnected hose.
(3) Start engine and observe gauge at idle. Vac­
uum gauge should read at least ten inches of mer­
cury.
(4) I f vacuum does not meet this requirement,
check for vacuum leaks or poor engine performance.
On diesel powered engines, refer to Group 5, Brakes
for vacuum pump diagnosis.
SPEED CONTROL SERVO
For complete speed control system diagnosis, refer
to the appropriate Powertrain Diagnostic Procedures
manual. To test the speed control servo only, refer to
the following:
The engine must be started and running for the
following voltage tests.
(1) Start engine.
(2) Disconnect 4-way electrical connector at servo
(Fig. 2).
(3) Turn speed control switch to ON position.
(4) Check for battery voltage at pin-3 of wiring
harness 4-way connector (Fig. 3). This is the 12 volt
feed from the stoplamp switch. When the brake pedal
is depressed, voltage should not be present at pin-3.
I f voltage is not present with brake pedal not
depressed, check for continuity between servo and
stop lamp switch. Also check stop lamp switch
adjustment. Refer to Group 5, Brakes for procedures.
(5) Connect a small gauge jumper wire between
the disconnected servo harness 4-way connector
pin-3, and pin-3 on the servo. Check for battery volt­
age at pins-1, 2 and 4 of the servo. If battery voltage
is not at these pins, replace the servo.
Fig. 2 Speed Control Servo Location
(6) Turn ignition switch to OFF position. Check for
continuity between disconnected servo harness