Generac Power Systems 9 kW NG, 10 kW LP Test 75 Check Oil Pressure Switch Wire, Do the following

DC control

Part 4

Section 4.4

Diagnostic tests

Test 75 – Check Oil Pressure Switch

And Wire 86

DISCUSSION:

If the oil pressure switch contacts have failed in their closed position, the engine will probably crank and start. However, shutdown will then occur within about 5 (five) seconds. If the engine cranks and starts, then shuts down almost immediately with a LOP fault light, the cause may be one or more of the following:

•Low engine oil level.

•Low oil pressure.

•A defective oil pressure switch.

PROCEDURE:

1.Navigate to the Digital inputs display screen.

a.Press “ESC” until the main menu is reached.

b.Press the right arrow key until “Debug” is flashing.

c.Press “Enter”.

d.Press the right arrow key until “Inputs” is flashing.

e.Press “Enter”.

DEBUG

INPUTS

INPUTS 1 - 8:

1 0 1 1 0 0 0 1

INPUT 1

Figure 41. The Home Page, Debug and Input Screens

f.Digital Input 1 is Wire 86 from the Low Oil Pressure switch to the board. Refer to Figure 41.

g.Set the AUTO-OFF-MANUAL switch to the MANUAL position.

h.Observe Input 1 for a change from "1" to "0". A change from "1" to "0" indicates that the control board sensed the LOP switch change states. If the generator still shuts down, replace printed circuit board.

i.If the input did not change states, proceed to Step 2

2.Check engine crankcase oil level.

a.Check engine oil level.

b.If necessary, add the recommended oil to the dipstick FULL mark. DO NOT OVERFILL ABOVE THE FULL MARK.

3.With oil level correct, try starting the engine.

a.If engine still cranks and starts, but then shuts down, go to Step 4.

b.If engine cranks and starts normally, discon- tinue tests.

4.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.Start the engine while observing the oil pres- sure reading on gauge.

c.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.

Figure 42. Oil Pressure Switch

5.Remove the oil pressure gauge and reinstall the oil pressure switch. Do NOT connect Wire 86 or Wire 0 to the switch terminals.

a.Set a VOM to measure resistance.

b.Connect the VOM test leads across the switch terminals. With engine shut down, the meter should read CONTINUITY. If INFINITY is measured with the engine shutdown, replace the LOP switch.

c.Crank and start the engine. The meter should read INFINITY.

6.Set a VOM to measure resistance.

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