Trane ACONT900AC43UA Service Manual page 184

Measuring Flame Current
Measuring flame current with a digital
multimeter
The procedure for measuring flame current is quite
simple. To perform the test, you will need a digital
multimeter capable of reading DC microampere cur-
rent.
Step 1
Disconnect power to the furnace
Step 2
Locate and unplug the 2 pin plug that leads to the
flame-proving rod (Figure 9.)
Figure 9
Step 3
Connect the positive lead from the voltmeter to pin 2 of
the flame sensor connector removed from the IFC board,
and place the negative lead from the multimeter to pin
2 of the flame rod connection terminal on the IFC board
(Figure 11.)
Figure 11
GF - F 4
Step 4
Set the multimeter to read DC microamperes (See
Figure 12.)
Figure 12
Step 5
Re-power the furnace and call for heat. The furnace
will cycle through the prepurge, energize the gas valve
and light the burners.
Step 6
When flame is established, read the flame current
level on your multimeter (Figure 13.)
Figure 13
Step 7
When complete, remove power to the furnace and re-
connect the 2 pin plug to the IFC board.
Step 8
Restore power to the furnace.