Electrical System with TX and TT Card
PS S5.0 5000
F-code Section C-code
Version no T-code
001 OE35
© BT Products
145 
Service Manual 1997-10-23
5. General Maintenance Instructions
The  SCR  control, like  all  electrical  apparatus, does have
some thermal losses. The semiconductor junctions have finite
temperature limits above which these devices may be
damaged. For these reasons, normal maintenance should
guard against any action which will expose the components
to  excessive  heat, such  as steam  cleaning;  or which will
reduce  heat dissipating  ability  of  the control, such as
restricting air flow.
The following 
DO’S
 and 
DON’TS
 should be observed:
Any controls that will be used in ambients of 100°F
(40°C) or over should be brought to the attention of
the truck manufacturer.
All external  components  having  inductive coils
must be filtered. Refer to vehicle manufacturer for
specifications.
The control should not be steam cleaned. In dusty
areas, use low-pressure air to blow off the control.
In oily or greasy areas, a mild solution of detergent
or denatured alcohol can be used to wash off the
control and then blow completely dry with low-
pressure air. The control can also be cleaned with
Freon TF degreaser.
For the SCR panel to be most effective, it must be
mounted against the frame of the truck. The truck
frame, acting as an additional heat sink, will give
improved truck performance by keeping the SCR
control package cooler. The use of a heat-transfer
grease (Dow Corning 340) is recommended.
Terminal boards  and other exposed SCR control
parts should be kept free of dirt and paint that
might change the effective resistance between
points.
The truck should not be plugged when
the truck is jacked up and the drive
wheels are in a free wheeling position.
The higher motor speeds can create
excessive voltages that can be harmful
to the control.
CAUTION