54-19

Wiring Changeover
>
>

A-Line
L-Line

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Cargo
Acterra

Condor

Sterling
Service Bulletin

Description of Revisions: This bulletin replaces the previous version dated July 2001. The changeover start date is corrected, and
a note is included in the General Information section about printed
wiring diagram books.

General Information
IMPORTANT: See Sterling SB 54-20 Inconsistent/Incorrect Wiring I.D.s for related information.
Starting February 27, 2001, L-Line, A-Line, and Acterra vehicles began being built with a new type of wiring system. This system is similar to the existing Acterra system and uses overlay harnesses. Wire harness circuit
numbering and color-coding have changed. Circuit numbering is now in the same format as the existing Acterra
system.
Wiring harness diagrams and schematics have been updated since the wiring changeover. To properly troubleshoot the new system, you must use the new diagrams and schematics. Diagrams are available on-line
through EZWiring.
NOTE: The Sterling A-Line/L-Line/Cargo Wiring Diagram Manual (STI-388) and the Acterra Wiring Diagram
Manual (STI-427.ML) include information for vehicles built BEFORE February 27, 2001.
IMPORTANT: Brake lights do not illuminate when the parking brakes are applied on L-Line and A-Line vehicles
built since the changeover to the new type wiring. This is also true for Acterra vehicles built before and since the
wiring changeover.

Wiring Changeover Highlights
Main Dash Harness
The main dash harness is wired for future use of the ICU IV (not yet released). A jumper harness attaches to the
instrument cluster (Ametek) or to individual gauges.

PLC Filter
A PLC (Power Line Carrier Communications) filter is incorporated into the trailer seven-way harness, running from
the power distribution box to the seven-wire female receptacle. The ABS trailer power supply and the ABS lamp
signal share a common wire. The PLC filter separates the signals, allowing one wire to perform two functions.

Fan Control Wiring
The air fan wiring has changed. The fan override switch is no longer wired through the A/C input to the engine
ECM (electronic control module). On vehicles with Caterpillar, Cummins, and Detroit Diesel engines, the override
switch (if installed) is normally closed and connected in series with the fan electric/air solenoid circuit (fail-safe
circuit). The electric/air solenoid is plumbed (for air) for normally open or normally closed operation, depending
on fan operation. For Mercedes-engined vehicles, a different switch (normally open) sends a ground signal to the
VCU (vehicle control unit).

J1939 Datalink
The J1939 datalink connectors and terminating resistors have changed. Splice-pack connectors are not used. Instead, Y-connectors are used to extend the harnesses outward or to install terminating resistors.

Sterling Service Bulletin, February 2002

Page 1

54-19
Sterling
Service Bulletin

Wiring Changeover
>
>

A-Line
L-Line

>

Cargo
Acterra

Condor

J1587 Junction Block
A J1587 junction block (similar to the Acterra) is located inside the cab on the driver’s side. It is a plug-in type
junction block and easier to connect to or disconnect from the datalink.

Bulkhead Connector A
Located on the lower driver’s side, the A-connector (previously a single 76-pin connector) has been replaced by
two smaller 34-pin connectors. The upper connector attaches the engine harness and the lower attaches the
transmission harness.

Bulkhead Connector B
Located on the upper driver’s side, the B-connector has not changed. It is a single 76-pin connector and connects half of the wires running to the power distribution box.

Bulkhead Connector C
Located on the passenger side, the C-connector (previously a single 76-pin connector) has been replaced by
two smaller 34-pin connectors. The upper connector attaches the other half of the wires running to the power
distribution box (those not coming from the B-connector). The lower connector attaches the chassis harness.

A/C Fan Cycling/High Pressure Switch
This is a four-terminal, normally closed switch providing A/C input to the ECM. The circuit loops the common (–)
ECM wire through the normally closed A/C switch and then back to the ECM A/C input.

Power Supplies
Many of the power supplies (engine, transmission, etc.) have been moved from the power distribution panel in
the cab to the power distribution box, outside of the cab. This reduces the amount of wires running into and out
of the cab and provides additional space around the power distribution panel.

Allison VIM
The Allison VIM (vehicle interface module) is no longer used and has been replaced by fuses and relays in the
power distribution panel.

Warranty
This is an informational bulletin only; warranty does not apply.

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Sterling Service Bulletin, February 2002