ST-47 Groundhog - Technical Manual
Servicing the ST-47
Page 14.
Procedure 1, Step D
Using the correct socket or hex wrench (Depends on ST-47 date of manufacture) remove the cover
fasteners and open the front cover. Using a at-blade screwdriver, remove the wires on intrinsically-
safe terminals TB2-2 and TB2-3. Using a Multi-Meter set on DC volts, measure the DC voltage
between terminals TB2-3 (+) and TB2-2 (-).
Is the voltage between 24 and 30 volts DC?
5.5 Test Procedure 2 - Stand-Alone Applications Only
Problem: The Ground Ball plug is connected to the tanker mounted Scully Ground Verication Ball
and RED non-permit lamp stays on. Unit does not “permit” externally connected devices.
Procedure 2, Step A
This step requires a Scully Ground Bolt or Ground Ball for testing- if you do not have one, Go to
Step A1. Use a jumper wire to connect the green wire on the bolt to the center pin inside of the plug
and connect the body of the bolt to one of the three tension ngers inside the plug. Does the
ST-47 Permit? If you have a Scully Ground Ball, attach the plug to it and touch the green wire to
exposed base of the Ground Ball.
Does the ST-47 Permit?
TIP
Ground Ball Connector Plug Maintenance
1.) Spring Finger Tension- Older styles of the Plug used an O-ring to tension the gripping
ngers which grip the base of the Ground Ball. The O-ring has been replaced by a new
tensioning ring (part# 31673) which provides a more positive grip.
2.) Contact Plunger Sticking- Severe weather conditions can cause the stainless steel
contact plunger (at the center, inside the plug) to stick in the down position. If it sticks it will
make a poor connection to the head of the Ground Ball. If it sticks, disassemble the plug and
apply white lube to the plunger where it contacts its plastic housing. To provide good contact
with the ball it must spring in and out freely.
NOYES
There is a wiring problem between the
ST-47 TB-2 terminals and the Junction Box
terminals. Correct the wiring problem
The ST-47 circuit module is defective. Replace
the module with a new one or, return the board
to the Scully Signal Company for repair or
Warranty consideration.
NOYES
Trailer grounding system is a fault. Have
tank owner check the installation or, contact
the Scull Service Department for assistance.
See TIP on Ground Ball Plug maintenance. If the
plug checks OK, go to procedure 2, Step A1.
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