SM14-001-0
Page 17/(18 Blank)
Check as follows:
1.
Use a DC voltmeter to measure the voltage at
the heater fuse. There must be 21 volts minimum
Motor is defective.
measured to ground. If the voltage is low check for:
Motor bearings need oil.
a.
Vehicle electrical system problems
Combustion air inlet is plugged or restricted.
b.
Loose or corroded connections
Blower wheels are loose on motor shaft.
c.
Poor ground
Carburetor or fuel mixer is not seated in burner
2.
If the supply voltage is within limits, check
head.
combustion air pressure as follows:
3.
If the air pressure is correct, check the fuel
a. You will need as 18-inch (457.2 mm) length
needle adjustment.
of 0.25-inch (6.35 mm) ID rubber hose, a football
a. Mark the position of the fuel needle slot in
inflation needle, and a tall jar or glass containing at
least 6 inches (152.4 mm) of water. Insert the inflat-
the carburetor body. Turn the fuel needle fully clock-
ing needle into one end of the rubber hose, and push
wise until it bottoms, and count the number of turns it
the inflation needle into the combustion air hose
takes. If full shutoff requires more than 1 3/4 to 2
between the blower and the burner head.
turns, flow rate is probably excessive.
b. Hold the START RUN OFF switch in the
b. Back out the fuel needle one full turn. Start
START position to obtain high blower speed, and
the heater.
immerse the end of the hose in the jar of water. Push
the hose deeper under the surface until the bubbling
c.
Allow the heater to run for a few min-
just stops. Measure the length of hose that is sub-
utes and observe the heat exchanger. When the fuel
merged; this length must be at least 4 inches. The
needle adjustment is correct, the first pass, or seg-
submerged depth represents the water column pres-
ment, of the heat exchanger will glow red, but no
sure produced by-the blower.
color will be visible on the next pass. There will be no
smoke from the heater exhaust.
c. If the air pressure is less than 4.0 inches
(101 .6 mm) of water, the air/fuel ratio will be incor-
d. If the heater does not burn in this manner,
rect. Check the voltage at the motor orange lead;
adjust the fuel needle in 1/4 turn increments, allow-
ing the heater to run for 5 minutes after each incre-
there must be 21 volts minimum. If the voltage is high
ment, until the heater burns as described in step c.
enough but air pressure is low, check the following.
