Beru Blue 12-volt oil-filled ignition coil, 3.5 ohm primary resistance — a classic-fitment ignition coil for restored 12V air-cooled VWs and other vintage European vehicles converted to 12-volt electrical systems. EMPI part #00-9403-B. The Beru Blue is a long-standing factory-look upgrade for owners who want a German-brand, period-appearance coil rather than a generic aftermarket unit.

Why a 3.5 ohm oil-filled coil

The 3.5 ohm primary resistance is the correct match for stock VW points ignition (Bosch distributor with internal points and condenser) on a 12-volt system. Running a coil with too low a resistance will burn through points quickly; too high and the spark will be weak at higher RPM. The 3.5 ohm spec is the factory match for the original Bosch 12V coils that this part replaces.

Oil-filled coils dissipate heat better than epoxy-filled coils, which matters in hot engine bays — particularly on air-cooled VWs where the coil mounts directly to the fan shroud and runs warm constantly. The trade-off is that oil-filled coils must be installed upright; mounting them upside-down or on their side will eventually cause oil to migrate and the coil to fail.

Specifications

• Voltage: 12 volts
• Primary resistance: 3.5 ohms
• Construction: Oil filled
• Color: Beru Blue
• Brand: Beru (German manufacturer)
• Part number: 00-9403-B

Fitment

• 12-volt VW Beetle, Karmann Ghia, Type 3, Bus, and Thing with stock points ignition
• Air-cooled VWs converted from 6V to 12V electrical
• Vintage Porsche, BMW, and Mercedes 12V applications using a 3.5 ohm coil
• Any 12V points-ignition vehicle where a 3.5 ohm coil is the factory spec

Will NOT work for: 6-volt electrical systems (use a 6V coil instead), modern electronic ignition systems that specify a low-resistance coil (typically 0.6–1.5 ohms — installing a 3.5 ohm coil with electronic ignition will produce weak spark).

FAQ

Will this work with Pertronix or other electronic ignition?
Check your electronic ignition module's specs. Most Pertronix Ignitor units (the basic version) work with a stock 1.5–3.5 ohm coil. Pertronix Ignitor II and III, and most Crane / MSD systems, require a lower-resistance coil. When in doubt, use the coil specified by your ignition module manufacturer.

Can I mount it sideways or upside down?
No. Oil-filled coils must be mounted upright (terminal end up) so the oil stays in contact with the internal windings. Mounting at an angle is acceptable; upside-down is not.

Is the Beru Blue better than the Bosch Blue?
Functionally they're equivalent — both are German-made, 3.5 ohm, oil-filled, 12V coils. Beru is the OE supplier on many vintage German cars; Bosch is the OE supplier on others. Either is correct for a restored 12V air-cooled VW.

Does it come with the mounting bracket?
This listing is the coil only — confirm bracket needs separately. If you're replacing a similar Bosch or Beru coil, your existing bracket will fit.

What's the difference between Beru Blue and Beru Silver/Red?
Color generally indicates voltage and resistance spec. Beru Blue is the 12V 3.5 ohm coil. Other colors in the Beru line have different electrical characteristics — match the color to your application.