20412578 Voltage Regulator | Genuine Volvo Penta Part

🔧 Product Description

Genuine Volvo Penta electronic voltage regulator for the 28 V, 35 A charging-system alternator family. This is the regulator specified directly for alternator 20412735.

🚤 Compatibility

Typically suits:

• Volvo Penta TD720GE
• Volvo Penta TD520GE

• Engine Family: TD

⚙️ Key Features

• Controls alternator field current and charging voltage
• Designed for nominal 24 V electrical systems
• Used with 28 V, 35 A alternators
• Requires alternator-number verification
• Electronic component is not repaired internally
• Engine type: Volvo Penta 5- and 7-litre industrial diesel

🔌 Function

Regulates alternator output near the specified 28 V charging level by controlling field current.

⚠️ Common Signs of Failure

• Battery not charging
• Charging voltage too high or too low
• Charge warning lamp remaining on
• Battery boiling or repeated discharge
• Intermittent alternator output

🛠️ Service Notes

• Isolate the batteries at the main switch and disconnect the negative lead before working on the charging circuit, and never disconnect a battery while the engine is running
• Rule out the simple causes before condemning a regulator — a slack or glazed drive belt, corroded or loose battery and alternator connections, a poor engine-to-battery earth, or a tired battery all produce the same symptoms
• Check the brushes and slip rings while the regulator is off; a worn brush set gives the same low or erratic output
• Fit clean and dry, seat any insulating washers and bushes in their original order so nothing bridges across them, and tighten the terminals firmly without crushing them
• Measure charging voltage at the battery with the engine running once the regulator is fitted, and compare it with the value specified for your engine and battery type

🔄 Supersession & Cross Reference

OEM / Related Numbers

• 20412735 - related alternator
• 20584337 - later 28 V 35 A alternator
• 20797555 - later regulator reference

OEM Reman Alternatives

• 3803512 - exchange alternator references
• 3803969 - exchange alternator references

📦 Condition

• Genuine Volvo Penta part
• Brand new
• Supplied in original or equivalent packaging