Westerbeke — Testing the Alternator
Testing & diagnosis · DC charging alternator
From a Westerbeke operator's manual covering: 16.0 BEDA, 20.0 BED, 25.0 BED, 32.0 BEDA. Check it applies to your exact model before use.
Applies to: Westerbeke 20.0 BED, Westerbeke 25.0 BED
Before you start
- A failed alternator can become very hot; do not touch until cooled.
- Do not use a high voltage tester (e.g. Megger) on the alternator charging circuit.
Procedure
- Start the engine.
- After a few minutes, measure starting battery voltage at the battery terminals with a multimeter on DC volts.
- Voltage should be increasing toward 14 volts; if so, alternator is working.
- If voltage remains around 12 volts, stop engine and inspect all wiring and connections.
- Check battery voltage with ignition on and engine off; should be 12 to 13 volts.
- Check voltage between alternator B+ output and ground with engine running; should be 13.5 to 14.5 volts.
- If only battery voltage at B+, check for 12 volts DC excitation at the EXC terminal and trace wiring.
Tools required
- Multimeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Alternator output 13.5 to 14.5 volts
- Battery voltage 12 to 13 volts, engine off
Full service-parts list: Westerbeke 20.0 BED →, Westerbeke 25.0 BED →
Source: Westerbeke operator's 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.