c. Check for 24 vdc between HEATER ON/PURGE ON switch (S4), terminals 1, 2, and 5, and ground.
(1) If voltage is indicated at terminal 2 but not at 1 or 5, replace switch.
(2) If voltage is indicated at terminals 2 and 1 but not 5, notify intermediate direct support maintenance to
repair jumper wire.
(3) If no voltage is indicated at 1, 2, and 5, disconnect wires from flame switch (S2) (6) and measure
across contacts for continuity. If infinity is indicated, replace S2 switch.
TM 3-4230-209-20&P
2-27