E-Type Series II
Alternator Swap Yet!
year, we documented the swap of a Nippondenso
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.
As was discussed in the Nippondenso
article, the Lucas alternator had several unique features:
alternator is very similar in appearance to stock unit. Clocking is identical
to the Lucas.
hand (CCW) rotation. Very few alternators come with fans designed for left
hand rotation. I'll discuss how to find a suitable fan for the
ear at 10 o'clock. The Bosch alternator has exactly this configuration.
alternating current output ("AL") for the ignition warning light
Automotive alternators are designed with the diodes located in the rear
(not the pulley end). The reason is that semiconductors can be damaged
by heat, and there's more room in the back for heat sinks and such. To
ensure proper cooling, the fan is usually mounted near the pulley, and
it's designed to pull air from back to front, so that the cool air hits
the critical diodes first. The fan is usually “clocked” to maximize airflow.
If you simply turn an alternator around backwards (pulley facing the engine),
it will spin counter clockwise, and the fan will pull less air. A 60 amp
alternator produces about as much heat as three light bulbs, so the air
hitting the diodes would be hot. Series II and III E-Types had reverse
mounted alternators. To accommodate this, the fans are designed to rotate
counter clockwise. Here's a comparison of CW and CCW fans:
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.
Blades Point Left
Blades Point Right
fan works either CW or CCW. Note: Blades are not angled.
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
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
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.
wiring plan: actually, very easy to adapt to the E-Type harness. The W~
connection doesn't appear on XJ6 wiring schematics. This unit may actually
be a 90A alternator from a 1990-93 VW.
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.
and modified circuits look like this:
Alternator requires minimal wiring changes.
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 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.
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.
Spacer fabricated from brass plumbing pipe.
Regulator/Brush Pack. Typically lasts 100K miles.
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relationship to CoolCat Express. While every effort has been made to make
these instructions accurate, CoolCat makes no warranty for the reader's
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.