Troubleshooting In The Shop - Emerson Fisher 846 Instruction Manual

Instruction Manual
Form 5739
February 2002
Before making the following checks, disconnect both
signal wires from the transducer, and ensure the
module final assembly is removed from the housing.
1. Using an ohmmeter, check the electrical
connections in the housing terminal compartment.
The circuit should show an open between the
positive (+) and negative (–) terminals. If not,
replace the housing or terminal block and connection
board.
2. Use a wire jumper to connect the two electrical
feedthroughs located in the module compartment.
The resistance between the positive (+) and
negative (–) terminals in the terminal compartment
should be 10 ohms. If not, check the electrical
feedthroughs for short or open circuits. If a short or
open circuit is found, replace the housing.
3. With the electrical feedthroughs jumpered as
stated above, connect the ohmmeter to either the
positive (+) or negative (–) terminal and the
grounding lug. The circuit should show an open. If
not, check for a short to the housing.
4. Remove the module from the module cover and
inspect the pilot/actuator assembly for damage or
clogging.
Some of the previous troubleshooting steps may be
inconvenient to perform in the field. It may be best to
make use of the modular design of the Type 846 or
Model 3311, and keep a spare, calibrated module
final assembly available for exchange. If the module
final assembly is to be transported to the shop for
repair, first remove it from the module cover. Attach
the spare module final assembly to the module
cover. Refer to Module Final Assembly in Section
6 for complete instructions. The nonfunctioning
module can then be returned to the shop for
troubleshooting.

Troubleshooting in the Shop

If the entire transducer is brought to the shop for
troubleshooting, then the preceding sequence
applies. If only the module final assembly has been
brought to the shop, then use another Type 846 or
Model 3311 housing as a test fixture. Insert the
module into the test fixture. Perform the previous
steps (as they apply) of the In-service
Troubleshooting procedure.
To further aid troubleshooting, the module final
assembly can be broken down into three
subassemblies. The troubleshooting sequence
consists of exchanging the subassemblies with
known working ones to determine which is at fault.
Troubleshooting
The three subassemblies are the pilot/actuator
assembly, the electronic circuit board, and the
module subassembly. The module subassembly
consists of the module final assembly with both the
pilot/actuator assembly and electronic circuit board
removed.
1. Remove the pilot/actuator assembly. Refer to
Pilot/Actuator Assembly in Section 6 for complete
removal information.
a. Inspect the nozzles and deflector. If they
show a buildup of contaminants, clean the
nozzles by gently inserting a wire with a
maximum diameter of 0.38 mm (0.015 inches).
Clean the deflector, if necessary, by spraying
with contact cleaner.
CAUTION
Do not apply force to the deflector bar
while cleaning the nozzles. Doing so
could alter the alignment or disable
the deflector bar mechanism.
CAUTION
Do not use chlorinated solvents for
cleaning the pilot/actuator assembly.
The chlorinated solvents will
deteriorate the rubber diaphragm.
b. Make sure the O-rings are lightly lubricated
with silicone grease and properly seated.
c. Reassemble and check operation.
d. If after cleaning the transducer does not
function, replace the pilot/actuator assembly with
a new one.
e. Reassemble and check operation.
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