Cummins/Onan 800 and 1200 Ampere Transfer Switch — Variable Resistor R4 Adjustment for Pilot Relay

For the Cummins/Onan 800 and 1200 Ampere Transfer Switch.

Browse Cummins/Onan generators & specs →

Procedure

1. Remove the disconnect plug and open the control panel.
2. Remove the wire lead(s) on the side of the resistor R4 from generator line B and the wire lead(s) on the side of the relay K4 coil from generator line A.
3. Connect an Onan Multi-Tester to the resistor and relay, or connect a Variac and accurate voltmeter.
4. If the resistor was replaced, set the slide on the new resistor approximately the same as the one removed.
5. Connect the Multi-Tester or Variac to a 120-volt AC source.
6. Vary the voltage from 0 to rated voltage. At approximately 85 to 90 percent of rated voltage, relay K4 contacts should close.
7. If resistor setting is correct, proceed to Step 12. If not, proceed to Step 10.
8. Remove AC voltage from the Multi-Tester or Variac and move the slide on resistor R4 a small amount.
9. Repeat Steps 8 through 10 until the correct resistor setting is obtained.
10. Remove AC voltage from the Multi-Tester or Variac, then disconnect and remove the voltmeter and Multi-Tester or Variac from relay K4 and resistor R4.
11. Reconnect the wire leads (removed in Step 6) to resistor R4 and relay K4.
12. Close the control panel and reconnect the disconnect plug.
13. Restore AC line voltage and connect the battery ground cables.
14. Move the operation selector switch to RMT (on engine control for two-wire starting) or to AUTO (in LT cabinet for three-wire starting).
15. Close the cabinet door.

Source: manual:922-0503 SECTION 2 LT AUTOMATIC TRANSFER SWITCHES.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.