Service manual
A DJM3.2 MANUAL
8. Ensure there are no burrs or dirt in the pilot line orifice and air tube. These items have often
been found with dirt, rust, insulation, paper, etc., blocking them. This includes checking the short
connector at the blower housing where the rubber tube attaches. Also ensure no capacitor
mounting screw is blocking the inlet to the pilot tube.
9. Usually changing the pilot assembly will not have much of an affect on the pilot signal if both
assemblies are in good condition and installed correctly.
10. Ensure the pilot assembly gasket is tightly installed to stop air leakage into the pilot area.
11. Standard (round) burner only. If the burner plate is not centered in the hole, it may allow too
much of a gap over the top of the burner, thus increased airflow through the larger opening may
roll onto the pilot box. Place a spacer under the burner plate to raise it into a centered position.
12. Due to the low capacities of some small units with standard (round) burners only, there may be
too much air entering into the pilot air tube. It may be necessary to reduce this air quantity by
placing a screw through the side of the combustion blower outlet in a manner that the screw also
passes through the metal tube that the rubber hose connects to. This normally only occurs on
units with an input of less then 300,000 BTUH. Some units have a screw mounted capacitor,
ensure the screw does not obstruct the pilot tube’s air path.
13. If a BMS signal is applied, caution should be taken about removing the transformer grounds that
may interfere with the BMS signal. It is possible that you may have disconnected the ignition
control or ignition transformer ground.
14. Water and ice have been located in the pilot gas lines, in the pilot air tube, in the pilot box, and in
the pilot gas orifice. Ensure these areas are free of moisture, locate the source and correct it.
15. Snow, ice, or water on the ignition control(s) can stop a pilot from igniting or proving. These
devices and their associated parts must be kept clean and dry.
Regulator Gas Pressure Responses
On some indoor units the vent orifice fitting on the RV appliance regulator is to be vented to
atmosphere. The field installed vent line should be sized adequately, especially on longer runs. If
there is more than one regulator connected to a common run, which includes the main regulator and
the line, is not adequately sized, changes in pressure on the RV diaphrams are applied to all
regulators. This includes the main regulator so an erratic inlet pressure will result and cause
improper combustion and also burner pulsating problems.
Some DJ unit manifolds have RV appliance regulators with a vent-limiting orifice, usually a brass
orifice marked ‘12A06’. Ensure that this tiny orifice is free of dirt or debris. A plugged orifice will
impede regulators opening flow and cause improper air/fuel mixtures.
If these are all OK, check the combustion settings. Either the manifold pressure is incorrect, orifices
plugged, the curve matching pot is set wrong, or the combustion air set incorrect. For further
information refer to the section for Combustion Set Up on page
29.
Pilot Sensing Problems
Check the condition of the pilot assembly. Check for damaged or dirty ceramics, damaged gasket,
and pilot set up. Ensure the pilot tube is free of debris and blockages. Note that there is an orifice
where the pilot gas line is connected to the pilot air tube. This orifice is sized to the BTU and altitude
requirements of the burner. It must be free of dirt and burrs to operate properly. If there are problems
lighting or proving the pilot that do not appear to be related to the ignition/flame supervision device
then carefully clean and inspect this orifice from both the gas tube and air tube side. If a burr exists it
is usually best to remove it by pushing it into the air tube from the gas tube with a small pin or orifice
drill, then break it off by inserting a object into the air tube.
If these are all OK, check the combustion settings. If the firing rate is too high, the curve matching
pot 1 is set wrong, or the combustion air is too low. Note previous section pertaining to combustion
set up and pilot set up for the style of burner you have (standard round, or high turndown rectangular
burner). If all the combustion parameters are correctly set, consult the factory.
Page 39 Revised: 3/11/99