GMC ST 350 1988, Wiring Diagram

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WIRING DIAGRAMS 11
W iring harnesses are joined by using a m ultiple plug
and receptacle connector block, or a term inal post
chassis junction block. In the instrum ent panel area
plastic insulated blade-type connectors and screw-type
term inals are used.
Each harness or wire must be held securely in place by
clips or other holding devices to prevent chafing of the
insulation.
WIRE SIZE
Wire size in a circuit is determined by the amount of
current, the length of the circuit and the voltage drop
allowed. Wire size is specified using the metric gage. The
metric gage describes the wire size directly in cross
section area measured in square millimeters.
WIRE SIZE
CONVERSION TABLE
METRIC
SIZE
(mm)2
0.22
0.35
0.5
0.8
1.0
2.0
3.0
5.0
8.0
13.0
19.0
32.0
40.0
50.0
62.0
AWG
SIZE
24
22
20
18
16
14
12
10
8
6
4
2
1
0
00
ON-VEHICLE SERVICE
CIRCUIT MAINTENANCE
AND REPAIR
MAINTENANCE AND REPAIR
All electrical connections must be kept clean and tight.
Loose or corroded connections may cause a discharged
battery, difficult starting, dim lights, and possible damage
to the generator and regulator. Wires must be replaced if
insulation becomes burned, cracked, or deteriorated.
To splice a wire or repair one that is frayed or broken
always use rosin flux solder to bond the splice and
insulating tape to cover all splices or bare wires.
When replacing wire, it is important that the correct size
wire be used as shown on applicable wiring diagrams or
parts book. Each harness or wire must be held securely in
place to prevent chafing or damage to the insulation due
to vibration.
Never replace a wire with one of a smaller size or
replace a fusible link with a wire of a larger size.
WIRING CONNECTOR TERMINAL
REPLACEMENT (BLADE TYPE)
Remove or Disconnect (Figure 16)
1. Terminal lock tang.
2. Terminal (61).
Install or Connect (Figure 17)
1. Pry up on the tang (70).
2. Terminal into the connector.
Figure 16—Removing the Terminals from
the Connector
WIRING CONNECTOR TERMINAL
REPLACEMENT (TWIN LOCK TYPE)
Remove or Disconnect (Figure 18)
Tool Required:
J-22727 Terminal Remover
1. Connector lock tangs.
2. Terminal locks using J-22727.
3. Terminal.
Install or Connect
1. Pry out the tangs.
2. Terminal into the connector.
WIRING DIAGRAMS 12
With the low current and voltage levels found in some
circuits, it is important that the best possible bond at all
wire splices be made by soldering the splices.
Use care when probing the connections or replacing
terminals in them, it is possible to short between opposite
terminals. If tnis happens to the wrong terminal part, it is
p o s s ib le t' at d a m a g e m ay be d o n e to c e rta in
c o m p o n e r :. A lw a y s use ju m p e r w ire s b e tw e e n
connectors for circuit checking. Never probe through the
Weather-Pack seals.
When diagnosing for possible open circuits, it is often
difficult to locate them by sight because oxidation or
terminal misalignment are hidden by the connectors.
Merely wiggling a connector on a sensor or in the wiring
harness may correct the open circuit condition. This
should always be considered when an open circuit is
indicated while troubleshooting. Intermittent problems
may also be caused by oxidized or loose connections.
Figure
17—
Resetting the Lock Tang
WEATHER-PACK CONNECTORS
Special connectors known as Weather-Pack connectors
(figure 19) require a special tool J-28742 for servicing.
This special tool is required to remove the pin and sleeve
terminals. If removal is attempted with an ordinary pick,
there is a good chance that the terminal will be bent or
deformed. Unlike standard blade-type terminals, these
terminals cannot be straightened once they are bent.
Make sure that the connectors are properly seated and
all of the sealing rings in place when connecting the
leads. The h inge-type fla p provides a back-up, or
secondary locking feature for terminals. They are used to
improve the connector reliability by retaining the terminals
if the sm all term inal lock tangs are not positioned
properly.
Molded-on-connectors require complete replacement of
the connection. This means splicing a new connector
assembly into the harness. Environmental connections
c a n n o t be re p la c e d w ith s ta n d a rd c o n n e c tio n s .
In s tru c tio n s are p ro v id e d w ith th e W e a th e r-P a c k
connector and terminal packages.
METRI-PACK CONNECTORS
The Metri-Pack connectors use a pull-to-seat type
terminal, as shown in figure 19. The special tool required
to remove the terminal is J-35689-A terminal remover. If
removal is attempted with an ordinary pick, there is a
good chance that the terminal will be bent or deformed.
Refer to figure 19.
Remove or Disconnect (Figure 19)
Tool Required:
J-28742 Terminal Remover
Primary lock (121) by lifting.
Connector sections.
Secondary lock (125) by spreading the sides of the
hasp, thus clearing the staples and rotating the
hasp (127).
Terminal (131) by using J-28742 (128).
• Snip off the old terminal assembly.
5 mm of the wire insulation (130).
Clean
Terminal barrel (124).
Install or Connect (Figure 19)
Terminal insulator (134) on the wire. Slide the
insulator back on the wire about 8 cm (3 inches).
Terminal (131) on the wire.
• Roll crimp (132) and solder the terminal.
Terminal insulator (134) and the roll crimp (133).
Terminal into the connector.
Secondary lock (125).
Connector sections until the prim ary lock (121)
engages.
4.
5.
EE
METRI-PACK CONNECTOR REPLACEMENT
Remove or Disconnect (Figure 19)
Tool Required
J-35689-A Terminal Remover
1. Primary lock (121) by lifting.
2. Connector body (137).
3. Connector seal (120) by pulling the seal back onto
the wires away from the connector body (137).