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Home›Repair guides›GENERATOR SET WILL NOT STOP WHEN LOAD IS REMOVED (SPEC A AND B)

Cummins/Onan — GENERATOR SET WILL NOT STOP WHEN LOAD IS REMOVED (SPEC A AND B)

For these Cummins/Onan models: 15.0 HA - 21 - a, 7.5 HA - 21 - a.

Applies to: Cummins Onan 15 0 Ha 21 A, Cummins Onan 7 5 Ha 21 A

Procedure

  1. 1. ié%) Put auto-manual switch in “MANUAL” position and stop generator set with start-stop switch on engine control. Remove the lead from the load side of the contactor in the demand control. . Move the auto-manual switch to “AUTO.” . If the engine cranks, proceed to Step 5. If the engine doesn’t crank, move auto-manual switch to “MANUAL” position. Start engine with engine start-stop switch. Move auto- manual switch to “AUTO” position and generator set should stop. This indicates there was sufficient load to keep the control energized. Remove the ground lead from the battery and the lead from terminal 3 to the engine. Check for continuity from the ground terminal in the automatic control to terminal 3 with the switch in “AUTO” position. This circuit should be open. If it is not, remove start-run relay. Check continuity from terminal 6 to 7. This should be open. Check continuity with 1- 1/2 volts or less from socket pin 8 to ground. Circuit should show high resistance (approximately 20,000 ohms) with positive on pin 8 and show a low resistance (approximatley 20 ohms) with negative to pin 8. See Load Sensor Board Component Tests (Spec A and B). 16 PRINTED CIRCUIT BOARD TESTS (SPEC C AND D) 300-0740 AND 300-0743 PRINTED CIRCUIT 8. Using the RX1 scale, check resistor R3. BOARDS Resistance should be 33 ohms. Remove the printed circuit board from the control. 9. 300-0743 Board Only: Resistance of resistor R5 Check components with an ohmmeter set at R X 100 (by start-run relay) and R6 (below fuse) should be . scale except where noted. Always recheck zero approximately 1500 and 160 ohms respectively. setting when changing scale settings. 300-0741 PRINTED CIRCUIT BOARD The volt-ohm-milliameter used must have Remove the printed circuit board from the control. batteries of 3 volts or less or diodes on the Check components with an ohmmeter set atR X 100 printed circuit board can be damaged during the tests. scale except where noted. Always recheck zero Serisi wa: setting when changing scale settings. With the printed circuit board positioned as shown in g ging scale settings Figure 4-21, start the tests on the left. All readings The volt-ohm-milliameter used must have given are approximate. } CAUTION | batteries of 3 volts or less or diodes on the printed circuit board can be damaged during the tests.
  2. 1. Condenser C1 and resistor R1 have a resistance

Source: manual:907-0500 Onan HA Auto Demand Control Service Manual (06-1984).pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.