Ttp49: Wire Shorted To Ground - Bosch D9412GV2 Troubleshooting Manual

D9412GV2/D7412GV2 | Troubleshooting Guide | 3.0

TTP49: Wire Shorted to Ground

Initial Actions
You must understand the devices and wiring splices
contained in the circuit you are troubleshooting. If you
do not know this information, trace the wiring as
required.
If you are unsure of which circuit to
troubleshoot, refer to Section
Identifying Addressable Points on a Circuit
on page 116.
If the circuit you are troubleshooting is
connected to equipment or a module with
its own AC power source that is not
ground isolated, the equipment or module
introduces a ground fault to the entire
system.
Procedure
Disconnect the conductor from the control panel or module.
Set your digital voltmeter (DVM) to measure resistance.
Connect the red DVM lead to the conductor and the black
DVM lead to a known earth ground.
If there is more than one conductor, test each
conductor using the red DVM lead until you identify the
conductor that is shorted to ground.
For the remainder of this TTP, leave the DVM
connected to this same conductor and earth ground.
Is there more than one piece of equipment connected to
this conductor, or are there wire splices on the
conductor?
Disconnect the other end of the conductor you are
troubleshooting.
Does the DVM still indicate a short to ground?
The problem is either that the disconnected
equipment is faulty, or the conductor is shorted
to ground. If the problem returns after
reconnecting the equipment, replace the
equipment.
A B
106
Troubleshooting
A
IMPORTANT: The rest of this procedure uses a half-
split troubleshooting approach. By answering the
following question, you divide the circuit in half to
determine the half of the circuit that contains the short
to ground. This half is the "affected circuit".
By repeating the question, you divide the affected
circuit in half again to determine the half of the affected
4.1.4
circuit that contains the short to ground. That half
becomes the affected circuit.
Repeat the following question as many times as
necessary until you reduce the affected circuit enough
to identify the location of the short to ground. Refer to
Figure 60
During the rest of this TTP, if the TTP states to "repeat
the process and question above", return to this
location in the TTP.
Disconnect the middle device or splice in the affected
circuit.
Does the DVM indicate a short to ground?
Refer to
where you disconnected the device or splice and either:
- the DVM, or
- the location of the device or splice you disconnected
the last time the DVM indicated an open to ground.
Reconnect the device or splice, then repeat the process
and question above.
Bosch Security Systems, Inc. | 11/05 | F01U011024B
B
Run the wire, then reconnect all equipment.
on page 107.
Refer to Figure 60 on page 107. The problem is
between where you disconnected the device or splice
and either:
- the end of the circuit, or
- the location of the device or splice you
disconnected the last time the DVM indicated a
short to ground.
Reconnect the device or splice, then repeat the
process and question above.
Figure 60 on page 107. The problem is between