Description
BOSCH F 00M 123 255 Rectifier – New Alternator Rectifier Assembly
The BOSCH F 00M 123 255 rectifier is a new alternator rectifier assembly from BOSCH. Converts AC to DC. £39.49. EU warehouse. Ships today.
Problem – Battery Light Glows Dimly, Batteries Drain Overnight
Your alternator charges fine when cold. After 30 minutes of driving, the battery light glows dimly.
You test the battery. Voltage reads 12.6V with engine off. Start the engine. Voltage climbs to 14V. Then it slowly drops back to 12.8V.
You replaced the voltage regulator. No change.
The BOSCH F 00M 123 255 rectifier is the component that fails in this scenario.
Root Cause – Failed Rectifier Diodes Leak AC Current
The rectifier converts AC current from the stator into DC current your vehicle needs. It contains six diodes arranged in a three-phase bridge.
When the F 00M 123 255 BOSCH alternator rectifier diodes fail, they stop blocking reverse current. AC leaks through. Your battery sees ripple instead of clean DC.
AC ripple destroys batteries. It causes internal heating. Plates sulphate. Electrolyte boils. Your battery loses capacity within months instead of years.
A multimeter on AC setting at the battery terminal tells the story. Healthy alternator reads under 0.5V AC. A failed BOSCH rectifier F 00M 123 255 alternator reads over 1.0V AC. Sometimes 3V or more.
For technical validation, BOSCH’s rectifier engineering documentation explains diode failure modes and AC ripple measurement.
Solution – BOSCH F 00M 123 255 Rectifier
BOSCH F 00M 123 255 rectifier is a genuine BOSCH rectifier assembly manufactured to original equipment specifications.
This BOSCH alternator rectifier contains six high-temperature diodes matched to specific alternator output characteristics. Each diode is rated for continuous operation at 150°C.
The BOSCH rectifier alternator uses a aluminum heat sink to draw heat away from the diodes. Proper heat sink design is critical. Overheated diodes fail shorted or open.
Install this BOSCH rectifier diode assembly. AC ripple drops to near zero. Your battery sees clean DC. Battery life returns to normal.
Fitment – Which Alternators Accept This Rectifier
This BOSCH rectifier fits specific BOSCH alternator frames based on physical dimensions and mounting pattern.
Compatibility logic:
Remove your alternator. Extract the existing rectifier.
Compare the mounting hole pattern and outer dimensions.
Count the number of diode connection points (this unit has 3 phase connections plus B+ and B-).
If the shape and mounting match, this BOSCH alternator rectifier is the correct replacement.
Do not guess fitment by vehicle model. Rectifiers vary by alternator frame. Always verify your old rectifier dimensions.
For cross-reference verification, search the BOSCH alternator parts catalogue using the part number F 00M 123 255.
Specifications for BOSCH F 00M 123 255 rectifier
| Specification | Detail |
|---|---|
| Item number | F 00M 123 255 |
| Trade numbers | BOSCH F 00M 123 255 |
| Manufacturer | BOSCH |
| Product type | Rectifier, alternator |
| Diode count | 6 (three-phase bridge) |
| EAN | 3165144148722 |
| Heat sink material | Aluminum |
| Condition | Brand New |
| Price | £39.49 |
Installation – Replacing Your BOSCH F 00M 123 255 rectifier Alternator Rectifier
Replacing the BOSCH rectifier requires alternator disassembly but not full rebuild.
Step-by-step:
Remove the alternator from the engine.
Remove the plastic cover from the rear of the alternator.
Remove the voltage regulator and brush holder if they sit over the rectifier.
Remove the three screws or nuts holding the BOSCH alternator rectifier to the alternator housing.
Desolder or cut the three stator phase wires from the old rectifier.
Remove the old rectifier.
Clean the mounting surface. Apply fresh thermal paste (if specified).
Position the new BOSCH rectifier alternator.
Solder or crimp the stator phase wires to the new rectifier terminals.
Secure the rectifier with screws/nuts.
Reinstall the regulator, brush holder, and plastic cover.
Reinstall the alternator. Test output voltage and AC ripple.
Warning: Rectifier replacement requires soldering. Use high-temperature solder (60/40 tin/lead minimum). Standard electronics solder will melt at alternator operating temperatures. Generator / Alternator Parts
FAQs – Diagnostic Questions for Alternator Rectifiers
Q: How do I know my alternator needs a BOSCH rectifier?
A: Dim battery light, batteries that fail prematurely, or AC ripple over 1.0V at the battery terminal. A multimeter on AC setting confirms rectifier failure.
Q: What is the difference between this BOSCH alternator rectifier and a universal rectifier?
A: BOSCH matches diodes to specific alternator outputs. Universal rectifiers use one-size-fits-all diodes that overheat or fail under commercial vehicle loads.
Q: Can I test the BOSCH rectifier alternator before replacing?
A: Yes. A multimeter on diode test mode checks each of the six diodes. Shorted or open diodes confirm rectifier failure.
Q: How long should a BOSCH alternator rectifier last?
A: 150,000-200,000 miles typically. Rectifiers fail more often than stators but less often than brushes.
Q: Can I install this BOSCH rectifier diode assembly myself?
A: If you have basic soldering skills and alternator disassembly experience, yes. If not, take the alternator to an auto electrician.
Q: What is the warranty on this product?
A: 30-day returns from autosparepart. BOSCH offers manufacturer warranty on material defects.
Trust Section – Why Buy From autosparepart
EU warehouse – Netherlands stock. Fast customs clearance.
Ships today – Orders before 2 PM CET dispatch same day.
Brand new – Genuine BOSCH. Factory sealed.
30-day returns – Unused rectifier in original packaging.
No minimum order – One rectifier or ten. Same fast service.
