Manufacturer: Johnson Controls
Description: SIGNAL TRANSDUCER
Category: Gas Controls
Y99AU-3 Signal Transducer
The Y99AU-3 signal transducer, used in conjunction with a hand-held
digital multimeter, allows for easy measurement of DC current down to
The Y99AU-3 allows current measurements to be read from the DC
voltage scale, using the conversion of 1 DC volt equals 1 DC
microampere. This conversion makes current measurements possible with
meters previously unable to read values in the micoampere range.
The signal transducer is designed to plug directly into the multimeter.
Observe the correct polarity. Failure to observe the correct polarity results
in negative values.
The Y99AU-3 can be used with any hand-held digital multimeter,
provided the meter has at least 10 megaohms of input impedance.
CAUTION: Equipment Damage Hazard. Label all wires prior to
disconnection. Wiring errors can cause improper and
dangerous operation. Verify proper operation after
Perform the following procedure to measure DC flame sensing current.
1. Set the selector switch on the multimeter to the DC voltage position.
The signal transducer makes it possible to check DC current by
reading the DC voltage scale and using a conversion of 1 DC volt
equals 1 DC microampere.
2. Turn off the power supply to the ignition control.
3. Disconnect the flame sensor cable from Terminal 4 on the ignition
4. Connect the 6.35 mm (1/4 in.) male spade to the flame sensor cable
5. Connect the 6.35 mm (1/4 in.) female spade to Terminal 4 on the
6. Disconnect the main valve lead from Terminal 3. This will prevent the
main burner from igniting. A proper measurement of flame sensing
current is taken with pilot light only.
7. Turn the power on and close the thermostat contacts to cycle the
8. When the pilot lights, read the current on the meter display using the
conversion of 1 DC volt equals 1 DC microampere. Refer to Table 1
for minimum current requirements.
9. Turn the power off and disconnect the meter.
10. Reconnect the flame sensor cable to Terminal 4 and main valve lead to
Replaces Part Numbers: Y99AU-3, CARY99AU-3