TRHS Troubleshooting Guide


Situation One: Pull red, pull-on/push-off switch to ON, but nothing happens; switch does not illuminate red.
Problem:  No electrical power to the TRH.


Organizational Maintenance Action:

  • Ensure that 120 VAC power is supplied to TRH. Ensure that power cable is securely fastened to the Amphenol fitting at TRH electrical control box. 

  • Ensure circuit breaker on TRH electrical control box is engaged. 
    If all of these conditions are satisfied and still nothing happens when the "ON" switch is pulled, fill out Equipment Repair Order (ERO) and request 3rd- echelon maintenance.

Intermediate Maintenance Action:

  • Isolate the faulty component by bypassing TRH electrical control box by connecting the burner power test cord to the top of the Airtronic Burner (unscrew and remove cable to electrical control box temporarily). If Airtronic Burner functions, replace red, pull-on/push-off switch in TRH electrical control box.

Situation Two: Pull red, pull-on/push-off switch to ON, but nothing happens; switch does illuminate red.
Problem: Not enough water in the TRH, Airtronic Burner control box in "lockout," mineral buildup on water-level sensor, or a combination of the above.


Organizational Maintenance Action:

  • Ensure that the water level in the TRH is above the water-level sensor.
    Push the round reset button on the Airtronic Burner control box.
    Clean the water-level sensor on the inside of the tank to remove mineral deposits.

  • If all of these conditions are satisfied and still nothing happens when the "ON" switch is pulled, one of the above mentioned components has failed. Fill out an ERO and request 3rd-echelon maintenance.

Intermediate Maintenance Action:

  • Isolate the faulty component by systematically bypassing each component by connecting the burner power test cord to the top of the Airtronic Burner (unscrew and remove cable to electrical control box temporarily) until the faulty component has been identified. Replace the faulty component.

Situation Three: Pull "ON" switch, motor runs but nothing else happens (no fuel spray from the exhaust pipe and the Airtronic Burner does not fire). Airtronic Burner then goes into "lockout."
Problem: No fuel in the Airtronic Burner, or faulty compressor solenoid.


Organizational Maintenance Action:

  • Ensure the fuel line to the Airtronic Burner is properly hooked up, with a serviceable fuel filter, there are no kinks in the fuel line, and the fuel can vent is open. Wait at least two minutes; push the reset button on the Airtronic Burner control box. Restart the Airtronic Burner while holding down the starting button inlet valve located on the side of the fuel pump.
    To create even greater suction, also close off the brass finger priming port with a finger. If the Airtronic Burner does not light after this procedure, repeat procedure one more time to allow adequate time for complete fuel line charging and Airtronic Burner priming. This may be necessary, especially with a new Airtronic Burner, new fuel filter, or a relatively long fuel line If there is still no fire, remove and replace the Airtronic Burner. Fill out an ERO and request 3rd-echelon assistance for repair.

Intermediate Maintenance Action:

  • Place Airtronic Burner on work bench and replace the control box with the test box. With the test box installed, turn on the switch to allow the motor and pump to run. Depress the starting button inlet valve and at the same time, cover the brass finger priming port with a finger. Maintain this dual priming condition for 40 seconds to 1 minute with only the one "blower" switch energized. Maintaining this condition for longer periods will not harm the equipment. Next, flip the "spark" switch and, looking down the burner tube, observe that the spark is blowing down in a spear-like shape. If the above priming exercise has been successful and no other problems exist, energize the third "number one solenoid" switch to allow atomizing air to exit the atomizers and create a spray, which should light instantaneously. If this procedure does not create a spray, one of two conditions exists. Either there is still no fuel reaching the atomizers or there is no air reaching the atomizers.

  • To best determine which of these problems exist, remove the front flange assembly with air tube and flame tube to fully expose the atomizing chamber with its dual atomizers. This can easily be done by removing the three screws that hold the front flange assembly to the lower fan housing. Now, turn on the "blower" switch while observing the surface of the atomizers. If a thin film of fuel can be seen passing over the atomizers, the problem is not with the fuel supply system. This observation should be made in a well-lighted area and can best be seen immediately after the "blower" switch is energized. It may be difficult to detect the thin film of fuel passing over the atomizers, so it may be necessary to exercise the switch several times while observing the surface of the atomizers. 
    If fuel is reaching the atomizers, yet there is still no fuel spray when the "number one solenoid" switch is energized, the compressor solenoid is faulty. Replace the compressor solenoid. Note that these symptoms refer to no fuel spray, not poor fuel spray. If a poor spray is noted, refer to the next problem symptom and action.

Situation Four: Airtronic Burner goes through normal prepurge, fuel mist exits the exhaust pipe, followed by either no combustion or unstable combustion. If there is no combustion, the Airtronic Burner will go into "lockout."
Problem: No ignition spark or improper ignition. The Airtronic Burner may also be running out of fuel or the atomizing chamber may have a clogged orifice.


Organizational Maintenance Action:

  • Remove and replace the Airtronic Burner in accordance with chapter 3. Fill out an ERO and request 3rd/4th echelon assistance for repair/replacement.

Intermediate Maintenance Action:

  • Replace the Airtronic Burner control box with the test box.
    Energize the "blower" switch to create a fuel flow over the atomizers. When the "arc" switch is energized, a good spark should be visible blowing downward in a spear-like shape. If so, the problem is not with the ignition system.
    If the spark is arcing over to ground or it is not stable across the ignitor probes, readjust the ignitor gap. If there is no evidence of a spark or arcing anywhere, check the ignition connections and if there is still no spark, replace the triangular-shaped ignition transformer adjacent the atomizing chamber, inside the lower fan housing. If the fuel supply is adequate, after following the procedure outlined in the preceding problem discussion, but the fuel spray appears weak or contains big droplets, install the compressor pressure gauge (shortest of three gauges) in the head of the compressor (remove brass fitting from compressor cylinder with a 4mm Allen wrench and screw in compressor pressure gauge) (figure 1-6). The pressure gauge should read about 2 psi when the air solenoid is not energized. When the "number one solenoid" switch is energized to provide compressed air to the atomizers, the pressure should be between 20-32 psi (25-27 psi is optimum). A pressure reading above 32 psi indicates a partially clogged orifice. The greater the pressure, the more severely clogged the orifice. If the pressure reading is above 32 psi, replace the atomizing chamber (figure 5-7). A pressure reading below 20 psi indicates poor compressor performance. Service the compressor by replacing the piston ring and O-ring assembly. If compressor pressure remains too low, replace the compressor cylinder (figure B-1). The inner walls of a faulty compressor will show signs of uneven wear. If the above problem is solved when using the test box, but persists when the test box is replaced with the Airtronic Burner control box, the Airtronic Burner control box is defective and must be replaced.


Situation Five: Pull ON switch, Airtronic Burner goes through prepurge and lights, but shuts down after a few minutes.
Problem: The Airtronic Burner is not being replenished with fuel from an external source.


Organizational Maintenance Action:

  • Make sure an external fuel line is installed, the fuel can has an adequate supply of fuel, and the vent screw to the adapter kit is properly opened.
    Check that the adapter suction probe in the fuel can extends below the fuel level.
    Prime the Airtronic Burner during pre-purge by depressing the starting button inlet valve as shown in chapter 4 (Figure 4-4)
    At the same time, close off the finger priming port with a finger to further enhance the priming process, as shown in chapter 4 (Figure 4-4)
    Make sure the fuel filter is not clogged and the fuel lines are connected properly and not kinked
    If, after repeated priming as described, the Airtronic Burner keeps running for a few minutes and shuts off, this indicates that fuel pump suction is marginal. Remove and replace the Airtronic Burner in accordance with chapter 3. Fill out an ERO and request 3rd-echelon assistance for repair/replacement.

Intermediate Maintenance Action:

  • Verify fuel pump malfunction by connecting the fuel pump pressure gauge (positively graduated) and the fuel pump vacuum gauge (negatively graduated) (both found in the maintenance kit) to the ports identified in figure 25-1. Both of these gauges are mounted on 1½-inch coupling extensions. First remove the metal screws in the ports with a 5mm Allen wrench, then gently screw the gauges into the ports with an adjustable wrench. Fuel pump pressure should read between .48 and .65 bars and fuel pump vacuum should read between .15 and .35 bars. Fuel pump vacuum lower than .36 bars may indicate a kinked fuel line, unvented fuel can, and/or clogged fuel filter. If these are not evident and fuel pump pressure is out of tolerance, replace the fuel pump. Removal of fuel sump will make fuel pump replacement easier. Drain the fuel sump first by opening the fuel sump drainage plug.

Situation Six: Any abnormal combustion problem such as smoke, rumbling, or combustion instability.
Problem: Less than optimum Airtronic Burner performance.


Organizational Maintenance Action:

  • Ensure that the fuel setting on the fuel flow control is between 1.0 and 1.5 kg/hr and the combustion air control is set at #9. In a static situation, the fuel setting need only be set at 1.0. In a fast-moving, off-road vehicle, a setting of 1.5 will provide superior combustion stability. A higher setting also simply heats the water faster 
    If this does not solve the problem, remove and replace the Airtronic Burner. Fill out an ERO and request 3rd-echelon assistance for repair/replacement.

Intermediate Maintenance Action:

  • Replace the Airtronic Burner control box with the test box.
    If the Airtronic Burner flame is not clean and uniform (absent "fire-flies," smoke, and odor) check for proper atomizing air pressures as previously discussed. If atomizing pressure is above the optimum range of 32 psi, replace the atomizing chamber.
    If the atomizing pressure is below 20 psi, replace the piston ring assembly and if below 16 psi, also replace the compressor cylinder. High compressor pressure indicates a clogged atomizing chamber that should be replaced.
    Low compressor pressure indicates poor compressor performance and the compressor O-ring and piston-ring assembly should be replaced. Also replace the compressor cylinder if a visual observation reveals surface wear along the cylinder wall.