Sierra INNOVA-MASS 241-VTP - Manual (Page 63)

Chapter 4 Troubleshooting & Repair Series 24-HP Instruction Manual
4-8 IM-24-HP
3. Using ESD precautions and hazardous area precautions, re-
move the electronics enclosure window cover. Disconnect the
temperature sensor (on the right) from the pressure / tempera-
ture board (the pressure / temperature board is the second
board below the microprocessor (display) board. Measure the
resistance across the outside pins of the temperature sensor
connector. It should read approximately 1080 ohms at room
temperature (higher resistance at higher temperatures). With
the temperature sensor still disconnected, measure the current
across the two outside pins of the exposed connector on the
temperature / pressure board. The current should be approx-
imately .0002 amps. Now reconnect the temperature sensor
and measure the voltage across the two inside pins (insert
probes into the connector where the wires enter it). This value
should be approximately .2 volts (or .0002 amps times meas-
ured resistance, .216 volts at room temperature).
4. Consult factory with findings
Symptom: Meter Displays Pressure Fault
1. For remote mounted electronics, carefully check all the wiring
connections in the remote mount junction box. There are 18
connections that must be correct, verify each color (black and
red), shield, and wire number.
2. Using ESD precautions and hazardous area precautions, re-
move the electronics enclosure window cover. Disconnect the
pressure sensor (on the left) from the pressure / temperature
board (the pressure / temperature board is the second board be-
low the microprocessor (display) board. Measure the resis-
tance across the outside pins of the pressure sensor connector,
then across the inside pins. Both readings should be approx-
imately 4000 ohms. With the pressure sensor still discon-
nected, measure the current across the two outside pins of the
exposed connector on the temperature / pressure board. The
current should be approximately .0004 amps.
3. Go to the first column of the hidden diagnostics and record the
Pe(V) and Pv(V) values and consult the factory with findings.
Electronics Assembly Replacement (All Meters)
The electronics boards are electrostatically sensitive. Wear a
grounding wrist strap and make sure to observe proper handling
precautions required for static-sensitive components.