Keystart control modules provide manual start/stop and automatic fault protection for generators, pumps and other engine-driven applications.

Outputs allow control of engine fuel (energized to run),  starter motor and preheat. The Keystart also has an alarm output for remote or audible warning of faults. Six LEDs and icons indicate engine status and faults. Four switch inputs (closing to negative on fault) enable automatic shutdown on engine low oil pressure, high coolant temperature and auxiliary faults. Model 9621 has a fully adjustable engine overspeed shut-down feature, configurable for either generator AC or magnetic pickup speed signals. Charge alternator excitation and a charge fail warning LED are standard.

Specifications Downloads How To Order

Power Supply

  • Operating voltage, steady state: 7 to 30VDC
  • Operating voltage, brown out/cranking: 5VDC minimum
  • Current consumption: <100mA


  • Fault switch inputs: close to negative DC during fault
  • Generator AC input (model 9621 only): 70 – 270 VAC rms, <50 to >60 Hz nominal
  • Magnetic pickup input (model 9621 only): 3.5 – 21 VAC rms, <2000 to >6500 Hz nominal

Outputs (all ratings non-reactive)

  • Run (fuel): positive DC, NO relay contacts, 10A max @ 24VDC
  • Start (crank): positive DC, keyswitch contacts, 10A max @ 24VDC
  • Alarm: negative DC (open collector transistor), 300 mA max
  • Speed calibration: to suit 0-1mA, 75 Ohm meter, output=0.75mA at rated engine speed.

Adjustable settings

  • Preheat timer: 0 or 10 secs, default = 0 secs
  • Fault override timer: 2 to 20 secs (VR1), default = 10 secs
  • Overspeed trip level (model 9621 only): 100 to 130% (VR3) of nominal calibrated speed, default = 110% (of 50 or 60 Hz)


  • Case material: polycarbonate / polyester
  • Overall dimensions: (w x h x d): 3.8 x 3.8 x 3.7 in. (96 x 96 x 95 mm)
  • Panel cut-out size: DIN 3.6 x 3.6 in. (92 x 92 mm)
  • Weight: approx 0.7 lb. / 300g
  • Operating temperature: -31° to 131°F / -35° to 55°C
  • Electromagnetic compatibility: EN55022, class B

Additional product documentation can be found on our product support website or by clicking the Help Center button above.

Part Number Model / Description Notes
41700141 KEY9620 (without overspeed protection) Only available from our UK office. Keyswitch Type K2, rubberized
41700143 KEY 9621 calibrated for 50Hz, (with overspeed protection, selectable AC generator or magnetic pickup sensing)* Only available from our UK office
41700142 KEY 9621 calibrated for 60Hz, (with overspeed protection, selectable AC generator or magnetic pickup sensing)* Keyswitch Type K2, rubberized
76701166 KEY7210 Keystart, no overspeed Only available from our UK office
76701167 KEY7211 Keystart, AC/MPU overspeed† Only available from our UK office
41700157 Spare mounting clips (pack of 4) Accessories / Spares
65700148 Spare keyswitch (K2 type), includes key Accessories / Spares
65000460 Spare key (K2 type) Accessories / Spares

* Factory default setting is for AC generator sensing, 50 or 60 Hz nominal. Non-standard (NS) setting options are available to order.

† Stock units are set to AC sensing, nominal 50Hz. To select magnetic pickup sensing, adjust internal circuit board link J1

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