Generac — Fixed Excitation Test / Rotor Amp Draw
Testing & diagnosis · Excitation circuit / Rotor
From a Generac service manual covering: GPS 12500, GPS 15000, GPS 17500. Check it applies to your exact model before use.
Applies to: Generac GPS 12500, Generac GPS 15000
Before you start
- If generator not producing AC, loss of governor control may cause overspeed; manually control throttle at 60 Hz / 3600 rpm
Procedure
- Unplug the six pin connector at the Voltage Regulator.
- Disconnect Wire 14 from the Resistor (R1).
- Connect jumper wire from removed end of Wire 14 to Wire 4 at Diode D1.
- Measure and record AC voltage across Wires 2 and 6.
- Measure and record AC voltage across Wires 11S and 44S.
- Remove jumper; measure DC rotor amp draw between Wire 14 and Wire 4 at D1.
- Shutdown; reconnect six pin connector and Wire 14 to R1.
- Match results with the Test 4 Results chart.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Voltage across Wires 2 and 6 above/below 60 VAC
- Voltage across Wires 11S and 44S above/below 120 VAC
- Rotor amp draw 12.5 kW 1.8 A; 15 kW 1.6 A; 15 kW (004582-2 Amazon/004987-1) 0.96 A; 17.5 kW 0.89 A, all plus or minus 20%
Source: Generac service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.