Caterpillar — Inaccurate Display - Troubleshoot
Testing & diagnosis · Digital Voltage Regulator
From a Caterpillar service manual — check it applies to your exact model before use.
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Procedure
- Stop the generator set and check the wiring; reverse the CT or PT polarity if incorrect.
- Start the generator set and load with 25% to 50% of rated load, using 0.8 power factor inductive load if possible.
- Check the values in parameters :04 and :05 and measure the ampere load on the B phase.
- Measure the signal voltage level at regulator terminals 5 and 6; verify it is in correct proportion to load amperes and agrees with parameters :04 and :05.
- If any parameters show negative numbers, a CT or PT polarity is incorrect or the phase rotation is wrong; verify polarity and rotation.
- Compare parameter :52 to actual generator current. If :52 reads less, slowly decrease parameter :05 until currents match; if more, slowly increase parameter :05.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Droop current transformer: no more than 5 VAC (RMS) at full rated load but not less than 3.5 VAC
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.