Guardian 4389 Repair Manual page 112

SECTION 4.4
DIAGNOSTIC TESTS
3. Do the following:
a. Disconnect Wire 86 and Wire 0 from the oil
pressure switch terminals. Remove the switch
and install an oil pressure gauge in its place.
b. Connect Wire 86 to Wire 0 for starting purposes
only. After engine starts, remove Wire 86 from
Wire 0.
c. Start the engine while observing the oil pressure
reading on gauge.
d. Note the oil pressure.
(1) Normal oil pressure is approximately 35-40
psi with engine running. If normal oil pres-
sure is indicated, go to Step 4 of this test.
(2) If oil pressure is below about 4.5 psi, shut
engine down immediately. A problem exists
in the engine lubrication system.
Note: The oil pressure switch is rated at 10 psi for
v-twin engines, and 8 psi for single cylinder
engines.
4. Remove the oil pressure gauge and reinstall the oil pres-
sure switch. Do NOT connect Wire 86 or Wire 0 to the
switch terminals.
a. Set a VOM to its "R x 1" scale and zero the
meter.
b. Connect the VOM test leads across the switch
terminals. With engine shut down, the meter
should read CONTINUITY.
c. Connect Wire 86 to Wire 0 for starting purposes
only. After engine starts, remove Wire 86 from
Wire 0.
d. Crank and start the engine. The meter should
read INFINITY.
5. Perform Steps 4a and 4b. If INFINITY is measured with
the engine shutdown, replace the LOP switch.
6. Set a VOM to it's "R x 1" scale.
a. Connect one test lead to Wire 86 (disconnected
from LOP). Connect the other test lead to Pin
Location 2 (Wire 86) of the J1 connector at the
Circuit Board. CONTINUITY should be mea-
sured. If CONTINUITY is not measured, repair
or replace Wire 86 between the LOP switch and
the J1 Connector.
b. Connect one test lead to Wire 0 ( disconnected
from LOP). Connect the other test lead to a clean
frame ground. CONTINUITY should be mea-
sured. If CONTINUITY is NOT measured repair
or replace Wire 0 between the LOP and and the
ground terminal connection on the engine mount.
7. If the LOP switch tests good in Step 4 and oil pressure
is good in Step 3 but the unit still shuts down with a LOP
fault, check Wire 86 for a short to ground. Set a VOM to
it's "R x 1" scale. Disconnect the J1 Connector from the
circuit board. Remove Wire 86 from the LOP switch.
Connect one test lead to Wire 86. Connect the other
Page 110
PART 4
test lead to a clean frame ground. INFINITY should be
measured. If CONTINUITY is measured, repair or
replace Wire 86 between the LOP switch and the J1
Connector.
RESULTS:
1. If switch tests good for Problem 9, proceed to Test 44.
2. Replace switch if it fails the test.
TEST 61- CHECK HIGH OIL TEMPERATURE
SWITCH
DISCUSSION:
If the temperature switch contacts have failed in a
closed position, the engine will not crank or start. If it
tries to start, it will immediately fault out on "Overtemp".
If the unit is in an overheated condition, the switch con-
tacts will close at 284ºF. This will normally occur from
inadequate airflow through the generator.
PROCEDURE:
1. Verify that the engine has cooled down (engine block is
cool to the touch). This will allow the contacts in the
High Oil Temperature Switch to close.
2. Check the installation and area surrounding the genera-
tor. There should be at least three feet of clear area
around the entire unit. Make sure that there are no
obstructions preventing incoming and outgoing air.
3. Disconnect Wire 85 and Wire 0 from the High Oil
Temperature Switch.
4. Set a VOM to measure resistance. Connect the test
leads across the switch terminals. The meter should
read INFINITY.
5. If the switch tested good in Step 4, and a true overtemper-
ature condition has not occurred, check Wire 85 for a
short to ground. Remove Connector J2 (5-pin) from the
circuit board. Set the VOM to measure resistance.
Connect one test lead to Wire 85 (disconnected from
High Oil Temperature Switch). Connect the other test lead
to a clean frame ground. INFINITY should be measured.
TESTING HIGH OIL TEMPERATURE SWITCH:
6. Remove the High Oil Temperature Switch.
7. Immerse the sensing tip of the switch in oil as shown in
Figure 28, along with a suitable thermometer.
8. Set a VOM to measure resistance. Then, connect the
VOM test leads across the switch terminal and the
switch body. The meter should read INFINITY.
9. Heat the oil in the container. When the thermometer
reads approximately 274°-294° F. (134°-146° C.), the
VOM should indicate CONTINUITY.
DC CONTROL