TM 3-4230-209-20&P
2-28
TROUBLESHOOTING (CONT)
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
WATER HEATER (CONT)
WATER HEATER DOES NOT HEAT WATER (CONT).
Step 6. Fuel pump and ignition drive motor operates in PURGE ON but does not operate in HEATER ON. Allow fuel pump and ignition drive motor
at least two seconds but not more than two minutes to start in HEATER ON. if motor does not start in two minutes do the following in order.
a. Pull thermal delay relay tubes TD1 and TD2 out and check each for resistance between pins 2 and 3. Replace any thermal delay
relay that indicates an open. With TD1 removed, check for 24 vdc between pin socket 2 and ground. If no voltage indicated, check
S4 switch, terminals 2 and 3, for 24 vdc.
(1) If 24 vdc is indicated at terminal 2 but not at 3, replace S4 switch.
(2) Reinstall TD1.
b. Check for 24 vdc between relay K2, terminal A1, and ground two seconds after heater control switch has been set to HEATER
ON. If no voltage is indicated at K2-A1, remove TD1 and check between socket hole 5 and ground for voltage. If voltage is at
socket hole 5, replace TD1 and retest. If still no voltage notify intermediate direct support maintenance.
c. Remove thermal delay relay tube TD2 and check for continuity from socket hole 5 to 7. If infinity is indicated, replace TD2 as
defective.
d. Check for continuity from TD2, socket hole 7, to switch S4, terminal 1. If infinity is indicated, notify intermediate direct support to
replace the thermostatic switch S1.
