OVERSPEED SWITCH INSPECT/TEST/REPLACE.
This task covers:
Multimeter (Item 12, Appendix B)
Tool kit, general mechanics (Item 1, Appendix B)
The overspeed switch is removed and installed in accordance with paragraph 2-28.
Inspect overspeed switch for evidence of burning or other damage.
Using multimeter, check supply voltage between terminals 1 and 2 of overspeed switch. Voltage should be +24
Vdc. If supply voltage is not present, check wiring.
Start engine in accordance with TM 10-4320-307-10 and allow to idle. Using multimeter, check voltage between
terminals 2 and 6. Voltage should be 11 Vac. If voltage is not. as stated, replace overspeed switch.
Connect a jumper between terminals 2 and 3. Increase engine speed to 1500 RPM and verify overspeed trip.
Remove jumper and verify +24 Vdc between terminals 2 and 7. If voltage is not as stated, replace overspeed
Restart engine and using multimeter, check voltage between overspeed switch terminals 2 and 7. Voltage should
be 0. If voltage is not as stated, replace overspeed switch.