Installing a Bosch, VW 120 A
alternator to a 1990 Range Rover Classic 3.9L with v-belts. Date of conversion Oct. 17, 2004
MY LEGAL STATEMENT.
This worked for me, but that doesn't
mean it will work for
you. Do this at your own risk!
I will not be held liable for your own actions.
If you hook-up a wrong wire, and burn your home or car down, thats your fault! I'm the first to my
knowledge to attempt this
alternator swap. If you feel you don't have the skills to do this, ask someone who does.
What you need:
VW Part # 021 903 025 G, more common part #s are 028 903 018 B or 028
903 018 C
Bosch Part # Bosch 0-123-510-007, -053 (refers to 021 903 025
Bosch Remanufactured Part # AL0184X
If you want to try this out, ask for 120 A alternator for the following
92-95 VR6 Corrado
94-99 Jetta GLX VR6, 95-99 Golf GTI VR6 (These are Mk3 bodies).
92-97 Passat GLX VR6
93-2004 Eurovan VR6 or Winnebago / Rialta RV camper.
Some auto parts stores may not carry the 120 A Bosch alternator, they
may have a 90 A Bosch or Valeo brand.
These 90 A alternators are common
with most of the VW line, only select VWs had a 120 A alternator.
With the redesign of VWs models from '99+ there are newer versions of
this alternator. The main difference is that the electrical plug is now
proprietary and oval shaped. The other difference is the rear black
plastic cover, depending on which model it was fitted to, may have
an air intake. Many newer Bosch alternators have this due to the
cramped engine bays, some are even water cooled.
### WARNING ###
DO NOT USE a Valeo brand alternator
with your RR. You will have a
problem with the Lucas pulley offset, the belt will not line up with
the p/s pulley. Try a local
rebuilder for a suitable pulley and shim, if your
determined to use the Valeo alternator.
This Bosch 120 A alternator sells on average for $220 (rebuilt), with a
core charge extra. New, they run $450-675.
I had this one lying around as a spare for my VR6 Jetta. Even better,
is a 150 A Bosch alternator, same exact case dimensions and plug type.
This is optional on the VW Eurovan and the Winnebago / Rialta RV
There is one weakness to this alternator, its the rear bearing noise.
Many VWs will have this noise start around 40K miles, its due to the
lack of sufficient grease. If you source a used alternator and want to
repack both the front and rear bearings. Please check out the following
page for a how-to. Bosch
alternator repair page.
This problem is common with VWs using this style alternator 70 A - 150
Total time to do this swap is about 1
1/2 hours tops, less if your
familiar with your Rovers engine.
Now onto the swap.
You will need to drill the Lucas pulley to 17mm ID so it will fit the
The orientation of the Lucas pulley is the same as if it were going on
a Lucas alternator. No need to flip it around, it works as is.
The pulley alignment is so close that it doesn't require any shims. I
put the Lucas pulley on without the original fan or other Lucas
All you need is the Bosch lock washer and nut. The Lucas fan
is not used, the Bosch alternator has an internal fan of its
To secure the Bosch alternator to the Range Rover lower bracket, mount
the front alternator ear on the outside of the RRC bracket. You
will need to use suitable nuts and bolts for the lower mounts and
for the upper mount.
requires some shims or a spacer of about 25mm long. This length can
vary a bit. due to the alternators sliding rear nut.
Original belt specified for use with the Lucas alternator, Autozone
part # 13270 is too short and tight with no adjustment possible.
purchased a much better fitting belt, Autozone part # 15290. This
is a 15mm wide belt versus the 13MM originally specified in the
parts computer. Infact the 15mm wide belt fits the pulleys better,
without sinking like the 13mm does. The 15290 belt allows for some
tension adjustment, without being too long or too short.
It helps to keep the bearings from failing prematurely, do not over do
There was no need to modify the upper Range Rover bracket at all. I did
notice that the previous owner had used a nut as a spacer, this is were
the top tensioner bracket bolts to the water pump. Good for me as I
didn't have to add it. I do not know if the Range Rover came from the
factory with a spacer there or not. If not, you need to get a longer
water pump bolt and use a 15mm spacer to keep the upper bracket from
binding on the alternators upper mounting ear. This spacer and longer
bolt is cheap, no need to weld an extender like others have with Delco
The wiring is so simple, once you know what the function of the wire
Your colors may vary, but my vehicle had the following colors:
Thick brown wire (battery lead), goes to alternator battery stud (Bat). I replaced it with a 4 ga. red
wire to the firewall terminal.
Brown with yellow stripe goes to D+
on Bosch alternator (dash light).
White with slate stripe goes to W
on Bosch alternator (tach lead).
No need for the Rover condenser, there is no noise heard over the radio
(after market sound system, 800w Sony 4 ch. amp). This Bosch alternator
has a condensor built into the rectifier assembly. The Bosch condensor
is not a serviceable part, it must be replaced with a new rectifier
I revised these measurements after
driving the truck, a more realistic
test as the alternator is hot. Original measurements were done with a
cold alternator, just after the swap. I originally had lower wattage
55/60W H4 headlamp bulbs, now they are
Voltage with accessories off was 14.04V, measured at the alternator
while the truck was parked idleing. Voltage with 90/100W H4 E-code
Hella headlamps, and 55W H3 Hella 550 driving lamps on was 13.96V at
I've read that these Bosch Alternators are hot rated, meaning they put
out 120 amp when its hot. Compare this to Domestic alternators which
are cold rated, the amperage drops as they get hot. I haven't confirmed
this, but I read this on a UK website dealing with Welding alternator
I have a single Red Top Optima battery, 4 ga. battery leads to the
chassis, starter and firewall terminal.
My voltage drop is due to the use of the original Rover battery cables
to chassis and to the starter (they are old). I had originally cut off
the old battery
clamps and soldered copper ring terminals for use with new Gold plated
battery clamps. These new clamps were sourced from a car stereo shop.
Only the alternator cable was made by me, but I did this nearly 5
months ago. I'll have to make those battery cables when time permits.
Its unrealistic to believe that I won't have a voltage drop, but I can
minimise the drop with new cables. Less resistance than the old 15 year
old cables = more voltage for my accessories.
Now onto the pics.
This is what the alternator will look like, with the stock VW
This alternator case style comes in 70 A, 90 A, 120 A and 150 A
Note my text and arrows.
This is where that part fits on your Range Rover.
These pics show the original 13270 belt, not the
I took the pics immediately after the swap. For the purpose of this
these pics will remain.
Looks at home in the Range Rover. 120 amps should be enough for
You can see there is plenty of adjustment left.
Pulley alignment, nearly dead on.
The dark side, note the rubber cap over the battery cable, sourced from
a mid 90's Mitsubishi Mirage, but doesnt fit the Bosch. Worked great on
the old Lucas alternator.
As viewed from above, note the W and D+ plug to the left of the battery
This is a W and D+ plug, its a standard Bosch engine sensor/ fuel
A simple plug to find at any auto parts store.
That pretty much covers it. A nice upgrade from the old Lucas 80 A
The tach works the same as if I still had the Lucas alternator.
The pulley diameter is original to the Range Rover, so it
should be accurate.
Now you can supply more current to your power hungry