Installing a Bosch, VW 120 A alternator to a 1990 Range Rover Classic 3.9L with v-belts. Date of conversion Oct. 17, 2004

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:
Bosch alternator.
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 G)
Bosch Remanufactured Part # AL0184X

If you want to try this out, ask for 120 A alternator for the following VW vehicles.
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 camper.

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 A.

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 Bosch alternator shaft.
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 hardware.
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 own.

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.
The rear 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.
I purchased a much better fitting belt, Autozone part # 15290. This is a 15mm wide belt versus the 13MM originally specified in the Autozone 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 the tension.

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 alternators.

The wiring is so simple, once you know what the function of the wire is.

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 or CD
(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 assembly.

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 90/100W.

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 the alternator.
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 kits.

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 pulley.
This alternator case style comes in 70 A, 90 A, 120 A and 150 A versions.

Note my text and arrows.
This is where that part fits on your Range Rover.

Bosch 120A
Bosch 120A

These pics show the original 13270 belt, not the new 15290.
I took the pics immediately after the swap. For the purpose of this page, these pics will remain.

Looks at home in the Range Rover. 120 amps should be enough for now.
Bosch 120A

You can see there is plenty of adjustment left.
Bosch 120A

Pulley alignment, nearly dead on.
Bosch 120A

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.
Bosch 120A

As viewed from above, note the W and D+ plug to the left of the battery cable boot.
Bosch 120A

This is a W and D+ plug, its a standard Bosch engine sensor/ fuel injector plug.
A simple plug to find at any auto parts store.
Bosch 120A

That pretty much covers it. A nice upgrade from the old Lucas 80 A alternator.
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 accessories.

Questions ?