B&C Model L40 Alternator

From $565.00 to $566.00
Description PN Price Buy
L40 Alternator with Boss Mount
L40 Alternator with Case Mount
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The L-40 Alternator from B&C Specialty Products is a high-performance, belt-driven alternator for Lycoming engines that make ideal power sources for aircraft requiring ample electrical output, modest weight, and exceptional reliability. Weighing just 6.1 lbs., it is produced from all NEW components (absolutely NO remanufactured content), and features sealed heavy-duty ball-bearings and built-in cooling fans to insure trouble-free service that gives you the best value for the long term.

There are similar-looking units on the market, but the similarity begins and ends there. Dynamically-balanced alternator rotors to promote good bearing and bracket life. Uniquely modify each alternator for use with a more sophisticated, aircraft style, external voltage regulator with over-voltage protection (such as LR3C-14 or LS-1A), instead of leaving in place an internal regulator better suited for automobiles. And on the L-40, a third attachment point to insure solid, stable support (look closely—many of the “look-alike” competing alternators only have two attachment points).

Available for both 14 volt and 28 volt applications, the L-40 Alternator comes complete and ready to install, with either a Boss Mount kit or Case Mount kit.

The Boss Mount kit for the L-40 mounts on the machined pad on the bottom of the engine opposite the starter and uses a U-shaped bracket and two 5/16" national coarse bolts.

The Case Mount kit for the L-40 mounts to the case halves by using the two 1/4" case half bolts.

L-40, BC460-H, BC410-H, and BC462-H alternators require external regulators - use: P/N 07-06742 (LR3C) for 14V Primary, P/N 07-06786 (LS-1A) for 28V Primary, P/N 07-03461 (SB1B-14) for 14V Standby, and P/N 07-03462 (SB1B-28) for 28V Standby.
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B&C products are all top quality!

Daffydd H Verified Purchase


October 18, 2021

High quality. Had to replace the belt from original alternator which required prop removal. New belt was included with alternator. . My original belt was a little too long for the B and C alternator

Steve H
January 20, 2021


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Is the B&C Model L40 Alternator FAA Approved for use in certified aircraft?

No, these kits are intended for use in experimental aircraft only.

Q: What is the difference between case and boss mount? I would like to purchase this alternator but I need it mount to the case of the engine via the case bolts under the engine.

The boss mount has a "boss" cast onto the crankcase. The case mount has a bracket that mounts to the spine bolts.

Most lycomings made in the last 3 decades have boss mount. The older engines are the ones with case mount. Boss mount is much better. The case mount brackets work but are subject to more bending and likely to crack easier. If unsure, please contact sales for clarification of which you need for your application.

Q: Does any wiring or plugs come with the L40 alternator part # 07-06815?

Yes, it will come with a pre-wired field connector.

Q: Does the L-40 Boss mount have the Voltage regulator built into it?

No. These require an external regulator.

Q: Does the case mount alternator come with a mounting bracket/tension arm or does it utilize the Lycoming mounting bracket/tension arm?

The L-40 comes with a kit that includes the bracket and tension arm.

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