Last year, we
documented the swap of a Nippondenso
alternator for the stock reverse-mount Lucas unit on S2 cars. I came
across a Bosch alternator that makes for a significantly simpler and more
powerful swap. It's a 90 amp alternator from an '88-92 XJ6, Lester# 13247.
This particular alternator had been rebuilt by Lucas (A2515) and possibly
misidentified as an XJ6 alternator. The alternator has a W~ connector,
which doesn't appear on the XJ6 schematic. I'll give instructions for connecting
an alternator with or without this connector. Instructions apply to E-Types
with reverse mounted alternators. This alternator can also replace forward
mounted alternators, by using a regular clockwise fan.
|Bosch alternator is very similar in appearance to stock unit. Clocking is identical to the Lucas.|
As was discussed in the Nippondenso article, the Lucas alternator had several unique features:
Note: Blades Point Left
Note: Blades Point Right
The Bosch comes with a clockwise fan. This was discarded and replaced with an omnidirectional fan, Prestolite (Electrosystems) part #90-2241. These are common aircraft components which can be obtained at reasonable cost. If you don't have a local aircraft supply house, try Aero Parts & Supply. The Prestolite fan includes an aluminum baffle. (Note: the Prestolite fan CANNOT replace the fan on a stock Lucas alternator. The hole is 17mm, while the Lucas shaft is 5/8") If you're trying to replace a regular forward mounted alternator, the XJ6 stock fan is fine.
|One of the issues with the Series II alternator is that it's mounted very high in the engine bay. To clear the bonnet, the tensioning lug is located at ten o'clock. The Bosch alternator (left) is perfect for the application|
|The Bosch mounts with a 3" double foot. The Lucas 45 amp mounts with a single 2" lug. Lucas 60 amp alternators have a double foot, similar to the Bosch. It's easy enough to adapt the Bosch unit to a Lucas mount.|
The Bosch alternator has a very adaptable wiring plan.. It has a large B+ terminal for the battery connection. The D+ lead is used for the warning light in it's original environment, but we'll simply connect the F+ lead in an E-Type. The small B+ lead is for a filter capacitor, which can be mounted to the case with the screw on the right. It has a connection (W~) which is similar to the AL lead on the Lucas alternator. From the viewpoint of the 3AW relay, it's an AL lead which can be used to control the ignition light in the dash. Naturally, we recommend replacing your 3AW with one of our solid state units.
When installing a larger alternator, it's important to think about whether the wiring can take the extra load. The key issue is the wire between the alternator B+ terminal and the battery. I ran a second 10 gauge wire, leaving the original wiring in place. Alternatively, you could run a single 6 gauge cable and replace the original wire entirely.
The pulley is a single V pulley, 2.75" in diameter. A local alternator shop or junk yard should be able to supply something suitable. The pulley from a Delco 10SI should be just about right. You can find one at Quick Start. It will be necessary to cut a groove for the Woodruff key on the Delco pulley.
The original and modified
circuits look like this:
|Bosch Alternator requires minimal wiring changes.|
|If the Bosch alternator doesn't have a W~ lead, then a little more work is needed. Completely disconnect the output from the alternator relay. Remove the AL and WL leads from the 3AW,and connect the wires with a short jumper. Optionally, add a small resistor in parallel with the dash ignition warning light. (The resistor will prevent non-charging in the event the bulb blows.) This has the virtue of eliminating both the 6RA and 3AW relays from the circuit.|
The physical installation
of the alternator is straight forward, although some light machine work
is needed to make it work. Since the Lucas mount is different, a spacer
needs to be fabricated to attach the alternator to the bracket. Simply
cut one out of 3/8" pipe, available in any plumbing shop. The spacer is
1 1/4" long. Since the alternator is designed to mount on a 8mm bolt,
you need to bore out the bushings to 3/8" to accommodate a larger bolt.
Drive the bushing out of the alternator, don't risk iron filings getting
into the core! Two bolts, rather than one, are used to secure the alternator
to the mount.
|Note: Spacer fabricated from brass plumbing pipe.|
One of the big advantages of the Bosch alternator is ease of repair. The Voltage Regulator and brushes are packed together, and can be replaced with a screwdriver in five minutes. This style of alternator has been used on millions of cars since the 1970's, the regulators all interchange.
Bosch Regulator/Brush Pack. Typically lasts 100K miles.
|I get 13.9 Volts with the A/C and headlights on at 600 RPM. At higher revs, I get 14.2 Volts consistently. It doesn't get better than this.|
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CoolCat Express Corp. All Rights Reserved. Linked vendors have no relationship
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accurate, CoolCat makes no warranty for the reader's own work.