Guardian Technologies 4270 manual TEST 38 - CHECK OIL PRESSURE SWITCH, 23. - Oil Pressure Switch

Section 7

DIAGNOSTIC TESTS

NOTE: For units out of warranty, refer to Quicksilver Diagnostic & Service Manual - Diesel, P/N 082034 for further engine service information. This manual can be found at www.guardiangener- ators.com, under “Brochures,Manual & Specs - Recreational Vehicle - Manuals”.

TEST 38 - CHECK OIL PRESSURE SWITCH

DISCUSSION:

Also see “Operational Analysis” on Pages 18-23. The Low Oil Pressure Switch is normally-closed, but is held open by engine oil pressure during cranking and startup. Should oil pressure drop below a safe level, the switch contacts will close to ground the Wire 85 circuit. Engine controller board action will then initiate an automatic shutdown.

If the switch fails CLOSED, the engine will crank and start, but will then shut down after a few seconds.

If the switch fails OPEN, low oil pressure will not result in automatic shutdown.

Figure 7-23. – Oil Pressure Switch

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 3, if “Continuity” is not indicated, replace the switch.

2.If oil pressure checked good in Step 5, but Step 4 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. 0E2081 for further engine service information. Verify that the oil is the proper vis- cosity for the climate and season.

4.If all steps check GOOD, go to Test 40.

TEST 39- CHECK CIRCUIT BOARD FOR

GROUND

DISCUSSION:

If the engine shuts down immediately after start switch is released, a possible cause would be the ground wire is faulty, forcing the unit to ground the cir- cuit board through the start/stop switch. Once the switch is released, the ground is removed from the board, causing the unit to shut down.

PROCEDURE:

1.Remove Wire 0 from the circuit board on Terminal 2.

2.Set a VOM to measure continuity.

3.Place one test lead on Wire 0, previously removed and the other test lead on clean ground. Continuity should be mea- sured.

4.Reconnect wire, making sure it has good contact on Pin 2 of the circuit board.

RESULTS:

1.If continuity was not measured in step 3, replace wire.

2.If continuity was measured in step 3, replace the circuit board.

TEST 40- TEST WATER TEMPERATURE

SWITCH

DISCUSSION:

This normally-open thermostatic switch has a sensing tip, which is immersed in engine coolant. Should coolant temperature exceed approximately 245-266 F, the switch contacts will close to ground Terminal 12 on the circuit board. Circuit board action will then shutdown the engine.

PROCEDURE:

1.Disconnect Wire 85 from the switch terminal.

2.Set a VOM to measure continuity.

3.Place one test lead on switch and the other on clean ground. Infinity should be measured.

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