Table 4-2. Unit Troubleshooting Guide (Continued)
TEST OR INSPECTION
Step 2. Check adjustment of the hold-fire thermostat assembly. The flame switch maybe opening.
(a) Refer to para. 4-60 for adjustment procedures. Replace the flame switch if adjustment does
not solve the problem (para. 4-60).
(b) Replace heater relay K1 (Reference Interconnection Diagram FO-2, Sheet 6) (para. 4-60).
(c) Replace heater (para. 4-60).
5. Diesel fuel heater remains on burner cycle after heat demands are met.
Step 1. Check adjustment of the hold-fire thermostat assembly, It may be out of adjustment, preventing op-
eration of the van thermostat.
Adjust thermostat assembly (para. 4-60).
Step 2, Check van thermostat operation. Disconnect the connector going to the thermostat controlling the
heater. Check for continuity across the A and B pins of the thermostat cable. Turn the thermostat to a
high temperature and check if the thermostat contact opens and then turn it down and check that the
Replace the thermostat if it does not cycle as described (para. 4-62).
Step 3. Remove the fuel solenoids on the carburetor and check for dirt on the fuel solenoid actuator lip.
Refer to para. 4-60 for procedures.
6. Diesel heaters do not operate off of the auxiliary power input.
Refer to power supply troubleshooting and auxiliary power circuit troubleshooting.
7. Diesel fuel heater exhaust drips fuel.
Step 7. If this happens during starting of the heater, refer to heater runs but no combustion troubleshooting
Srep 2. If this happens during operation, refer to heater backfires troubleshooting and adjust the fuel control
8. Fumes from the diesel heaters in the ROWPU van.
W A R N I NG
The exhaust pipes can reach temperatures exceeding 600 degrees. Do not touch the
exhaust pipes without putting on protective gloves first. Do not touch them with bare
Remove the exhaust pipe shrouds and check if the fumes are being blown back into the ROWPU
through the exhaust pipe gaskets.
Replace the exhaust pipe gaskets if they are leaking (para. 4-60).
Check if pipe has been added to the exhaust to make it vent farther from the ROWPU. Refer to opera-
tors troubleshooting if pipe has been added to the ROWPU exhaust. If pipe has been added and it has
arise to it, check that a condensate drain hole is located at the low point of the piping and that it has not
frozen over allowing ice to buildup in the piping. This will cause backpressure on the heater combus-
tion chamber and allow exhaust fumes to back up in the ROWPU.
Remove pipe in excess of recommendations and remove any ice that maybe blocking the exhaust.
Check the exhaust for smoking and backfiring.
If the exhaust is smoking or dripping fuel refer to those symptoms in heater troubleshooting (mal-
If the wind is blowing straight at the exhaust pipes, erect a wind block to reduce backpressure on the
(a) If the wind block eliminates the problem of fumes operate with the wind block in place or repo-
sition the equipment so that the wind is not creating backpressure on the exhaust.
(b) If the wind block has no effect, replace the heater (para. 4-60).