Caterpillar — No Voltage - Troubleshoot
Testing & diagnosis · Cat Digital Voltage Regulator (CDVR)
From a Caterpillar service manual — check it applies to your exact model before use.
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Before you start
- Electrical shock/electrocution hazard; service by trained personnel only.
- Terminals and heat sinks are live at hazardous voltages when power is applied and for up to 8 minutes after power is removed.
Procedure
- Verify all wiring is properly connected per wiring diagrams.
- Verify generator is running at rated speed.
- Determine if regulator is PMG powered or shunt powered.
- Check for correct input power to the voltage regulator per Electrical specification.
- Verify residual voltage applied to power input is at least 6 VAC; flash generator field if not.
- Verify fuses are not open; replace any open fuses.
- Verify CDVR is connected to 24 VDC control power.
- Verify common alarm/Shutdown LED is not flashing; if flashing, check for protective shutdown fault.
- If EDM (Exciter Diode Monitor) fault occurred, check rotating exciter diodes for open/shorted diodes.
- If over excitation fault occurred, check generator/load for fault and check for loose sensing connections.
- If loss of sensing fault occurred, check for loose/open connections to voltage sensing inputs.
- If field over current fault occurred, check generator/load conditions and connections.
- If internal memory failure fault occurred, reset regulator; replace if fault recurs.
- If internal watchdog failure fault occurred, reset regulator; replace if fault recurs.
- Replace the voltage regulator unit if prior steps do not correct the problem.
Source: Caterpillar 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.