DIAGNOSTIC PROCEDURES - HEATER TESTING
There are various configurations of electric pre-heaters and
thermoswitches available for the Fuel Pro . These include
12VDC pre-heaters, 24VDC pre-heaters, 120VAC pre-heat-
ers/thermoswitches, and combination pre-heater thermo-
switches . The voltage and wattage ratings are stamped
either on the sheath or the hex of each component for
identification .
Equipment Needed
• A precision low resistance ohm meter capable of mea-
suring 1/10th ohm or less .
• Current flow meter (clamp-on type for DC current) .
• Ice, dry-ice, CO2 or some means of chilling the thermo-
switch .
• A flameless source of heat . (ie: infrared heat lamp, etc .)
Note: A Vortex tube is a good tool to heat and cool for
testing .
�
DO NOT USE a test light that has a wire probe
for any of these tests. If the wiring insulation is
punctured, moisture and road salt can penetrate
into the wires creating a corrosion issue and
potential failure.
Draining the Fuel Pro
1 . Shut off the engine and set the parking brake .
2 . Attach a length of hose to the drain valve and place a
receptacle under the Fuel Pro .
3 . Loosen the vent cap on top of the clear housing . Open
the drain valve and drain the fuel into the receptacle .
4 . When the fuel is drained, close the drain valve .
Pre-heater Operation Test
1 . Disconnect the pre-heater from the harness .
2 . Connect the ohm meter leads to the pins of the pre-
heater . For heaters with one pin, connect to the pin and
the bushing . Use the following to determine whether the
pre-heater resistance value is in the acceptable range .
Pre-heater
Watts
Resistance Range (ohms)
12VDC (two pin)
250 W
0 .6 to 0 .8 @ 77°F (25°C)
12VDC (single pin) 250 W
0 .6 to 0 .8 @ 77°F (25°C)
12VDC (single pin) 150 W
0 .8 to 1 .1 @ 77°F (25°C)
12VDC (two pin)
150 W
0 .8 to 1 .1 @ 77°F (25°C)
24VDC (two pin)
250 W
2 to 2 .5 @ 77°F (25°C)
24VDC (single pin) 250 W
1 .8 to 2 .3 @ 77°F (25°C)
24VDC (single pin) 150 W
3 .6 to 4 .1 @ 77°F (25°C)
24VDC (two pin)
150 W
3 .6 to 4 .1 @ 77°F (25°C)
120VAC
75 W
173 to 203 @ 77°F (25°C)
120VAC
37 W
369 to 411 @ 77°F (25°C)
Combination Pre-heater Thermoswitch Perfor-
mance Test
1 . Disconnect the harness from the heater/thermoswitch
combination unit .
2 . Using one of the cooling methods listed under "Equip-
ment Needed", reduce the temperature of the thermo-
switch to below 40° F .
3 . Connect the ohm meter leads to the pre-heater pins .
Use Table 1 to determine whether the pre-heater resis-
tance value is in the acceptable range .
4 . Using one of the pre-heating devices listed under
“Equipment Needed”, raise the temperature of the com-
bination pre-heater to 70°F . The ohm meter should read
“open circuit” for the combination units .
12 VDC PTC/24VDC Performance Test
1 . Disconnect the harness from the heater .
2 . Connect the ohm meter leads to the pins of the heater .
Use the following to determine whether the pre-heater
resistance value is in the acceptable range .
PTC Heater
Watts Resistance Range (ohms)
12VDC (PTC)
195 W
0 .4 to 0 .6 @ 77°F (25°C)
24VDC (PTC)
195 W
2 .0-3 .0 @ 77°F (25°C)
12VDC (PTC)
155W
0 .95 to 1 .2 @ 77°F (25°C)
FUEL PRO
®
382
TECHNICAL MANUAL
T e c h n o l o g y , L L C
DAVCO Technology, LLC P. O. Box 487 Saline, MI 48176 Call 800-328-2611 www.davco.com F1271 REV J
October 3, 2016 11:34 AM
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