Check Oil Temperature Switch - Guardian 4700 Repair Manual

PROCEDURE:
1. Check engine oil level. If necessary, replenish oil level to the
dipstick "FULL" mark.
2. Set a VOM to its "Rx1" scale and zero the meter.
3. Connect the meter test leads across the switch terminals, with
engine shut down. The meter should read "continuity". A small
amount of resistance is acceptable.
4. Crank the engine. Oil pressure should open the switch contacts
at some point while cranking and starting. Meter should then
indicate "infinity".
5. If the contacts did not open in Step 5, remove the low oil pres-
sure switch and connect an oil pressure gauge in it's place.
Start the engine and measure oil pressure. Pressure should be
above 10 psi.
RESULTS:
1. In Step 4, if "continuity" is not indicated, replace the switch.
2. If oil pressure checked good in Step 6, but Step 5 measured
"infinity," replace the low oil pressure switch.
3. If oil pressure is below 10 psi, determine cause of low oil pres-
sure. Refer to Engine Service manual No. 0C1103 for further
engine service information. Verify that the oil is the proper vis-
cosity for the climate and season.
TEST 40 - TEST OIL TEMPERATURE SWITCH
DISCUSSION:
If the engine cranks, starts and then shuts down, one
possible cause of the problem may be a high oil tem-
perature condition. Protective shutdown is a normal
occurrence if the oil temperature switch exceeds
approximately 284°F (140°C).
Figure 7-33. – Oil Temperature Switch
PROCEDURE:
1. Remove Wire No. 85 from Oil Temperature Switch terminal
and start the generator. If engine starts and runs now, but
shuts down when Wire 85 is connected to the switch terminal,
the following possibilities exist:
a. Oil temperature is too high.
b. The oil temperature switch has failed closed or
is shorted to ground.
2. Remove the switch and place its sensing tip into oil (Figure 7-
33). Place a thermometer into the oil.
3. Connect the test leads of a VOM across the switch terminals.
The meter should read "infinity".
4. Heat the oil. When oil temperature reaches approximately
284°F (140°C), the switch contacts should close and the
meter should read "continuity".
Figure 7-34. – Testing Oil Temperature Switch
RESULTS:
1. If the Oil Temperature Switch fails Step 3 or Step 4, replace the
Oil Temperature Switch.
2. If the Oil Temperature Switch is good, an overheat condition
may be occurring. Verify that the installation of the generator is
within specified tolerances. The generator must receive the
proper amount of incoming air, and also be able to exhaust the
cooling air with NO RESTRICTIONS. Check to be sure that the
exhaust pipe is not under the air intake. Refer to the Owner's
and Installation Manual for proper installation specifications.
Section 7
DIAGNOSTIC TESTS
Page 51