Global Machinery Company Sierra 1999 - Manual (Page 259)

yellow blue
4-69
Instrument Panel Jumper Wiring Harness
This harness is included with the heavy-duty and
camper/fifth-wheel trailer wiring packages. The harness
is for an electric trailer brake controller and includes a
trailer battery feed fuse. This harness and fuse should be
installed by your dealer or a qualified service center.
Auxiliary Battery (If Equipped)
The auxiliary battery provision can be used to supply
electrical power to additional equipment that you may
choose to add, such as a slide
- in camper.
If your vehicle has this
provision, this relay
will be located on the
passenger’s side of the
vehicle, next to the
auxiliary battery.
When using this provision, connection should only be
made to the upper stud (A) of the relay. Do not make
connections to the lower stud (B) of the relay.
The auxiliary battery circuit is protected by a Megafuse
located behind the auxiliary battery.
Be sure to follow the proper installation instructions that
are included with any electrical equipment that you install.