Time to start main subject, which will describe how to play with it, not how to fix it under an hour, this guide is for people loving the challenge and with attention to details.

We’re looking at Bosch 115amp alternator:

Known  symbols (so far):

0 120 468 025

0 120 468 026

0 120 468 027

Consumables involved:

-       Bearing front 17x52x17mm (rare rumour say that some of those are having 17x47x17mm): £10 to £18

-       Bearing rear 12x32x10mm: £3 to £6

-       Slip Ring - id17.00, od28.00, h22.00, h-total25.10, groove1.90, 2xland 10mm each: £3

-       Regulator brushes - L19.40, W8.00, T4.90, L-cable:50ish mm (pair): £1

If you still don’t know how bearing dimensions are reported – leave now, there is nothing for you below.

Let’s look closer to every consumable part involved in your big project with small budget:

1.     Bearing front

Also known as main bearing, list of manufacturers worth your attention below (including part numbers):

1120905012 - BOSCH

1120905017 - BOSCH

1120905036 - BOSCH

1120905048 - BOSCH

1120905049 - BOSCH

1120905054 - BOSCH

1120905055 - BOSCH

1120905062 - BOSCH

1120905070 - BOSCH

1120905084 - BOSCH

1120905086 - BOSCH

1120905089 - BOSCH

1120905093 - BOSCH

1120905094 - BOSCH

1120905095 - BOSCH

1120905096 - BOSCH

1120905506 - BOSCH

1120905520 - BOSCH

1120905531 - BOSCH

F00M990417 - BOSCH

F00M990425 - BOSCH

F00M990426 - BOSCH

F00M990434 - BOSCH

565007 - FAG

806078 - FAG

F-806078 - FAG

8.8121.0 - IKA

8.8212.0 - IKA

B17-99DDW -NSK

SC0352LLUACLW - NTN

592905 -VALEO

592936 -VALEO

593674 -VALEO

1.     Bearing rear

Well known for tendency to lose seals due to dust from the brushes/slip ring. Consequence – nice flame from burning bearing and sound of grinding – easy to confuse with loose cam chain:

62012RS – NSK, NTN

1120905002 - BOSCH

1120905008 - BOSCH

1120905022 - BOSCH

1120905023 - BOSCH

1120905025 - BOSCH

1120905026 - BOSCH

1120905028 - BOSCH

1120905029 - BOSCH

1120905030 - BOSCH

1120905032 - BOSCH

1120905033 - BOSCH

1120905038 - BOSCH

1120905040 - BOSCH

1120905042 - BOSCH

1900905230 - BOSCH

1900905232 - BOSCH

1900905275 - BOSCH

949100-0150 - DENSO

949100-0350 - DENSO

949100-1000 - DENSO

949100-1420 - DENSO

949100-1980 - DENSO

6201-C-2HRS-C3 - FAG

62012HRSC3 - FAG

62012RSRC3 - FAG

6201 2RSH/C3 - SKF

62012RS1 - SKF

590568 - VALEO

592613 - VALEO

592907 - VALEO

1.     Slip Ring

Now here’s the problem, those things are not easy to get… Unless you know how to call it and how cheap it is. My ultimate choice of manufacturer have-it-all is completely unknown company called AS-PL, which is a stockist with some manufacturing lines. Even with the fact that those fuckers won’t sell you anything (instead they’ll send you to some sheep-shagging “distributor” without even a website or email) – their products can be found across the Internet. Part number in your interest is: AS-PL ASL9006. It will fit both types of rotor – knurled and plain (you will find both depending on generation of the alternator).

2.     Regulator brushes.

Well, why should you play with this shit instead of buying complete replacement regulator for £5.10? The answer is – stability/reliability. If you have genuine Bosch, buy new Bosch (£50-120) or simply change the brushes – it’s damn easy! Just don’t block yourself in your safe space… Again, AS-PL product is the way forward, any other with similar dimension as an alternative.

Chapter 1: Bosch 115A Alternator Disassembly

Start from giving it a good clean from outside. This is mandatory if you don’t want to smear the shit all over you bench/tools each time you’re fiddling with it.

At this point I highly recommend purchasing product similar to my very best friend met not long ago by myself. That’s right - battery-powered IMPACT WRENCH. No, not this shit advertised in Tesco or Walmart. Choose branded product like Milwaukee, DeWalt, Bosch, Makita – why? Simple reason – accessories and batteries for no-name shit products – will cost almost the same as the genuine ones for well-known best-sellers (check yourself).

Now, I am not telling it is impossible to disassemble this specific alternator without impact wrench – actually my first one was stripped with hand tools and power of my muscles… It was a fucking disaster, complete waste of time and calories ended up with use of cobalt drills, blow torch, hammer, and diamond cutters / Bosch GRO (Dremel sucks). You can do it without impact wrench, you can gain up experience level just like me…

So here it is, collection of the tools for the upcoming task:

Bearing puller, impact wrench, soldering iron and Dremel torch, multimeter, Dewalt bits, electronics lacquer can, slide hammer, etc…

WARNING NOTE:

Be extra careful with Stator winding!!! It will be exposed after removal of top housing. Any bump, drop, scratch and you may be £30 lighter.

1.1 Jaguar XJS Alternator Withdrawal

First and as you probably expected – you will need to detach your alternator from the engine. This is childish as you need to loosen the belt tensioner undo few screws/bolts and remove the main alternator bolt… The main bolt which is a real bitch. The real bitch if you’ll have an honour to remove it as a first person since your banger left the 3-day-working-week-factory in UK. With limited access only thing left is to spray the entire area with Liquid Wrench and use ratchet to spin it dozens of time until it becomes loose enough to bang it our with a hammer (2.0lbs minimum). Here's the secret. Just watch the photos below:

Oh, by the way - if you are wanker enough to do it with battery attached – you will probably experience some fireworks on the way…

Oh, by the way 2 – undo two screws and remove capacitor and voltage regulator entirely. You don’t need those for now. If you’ll forget – I bet you are going to break it during rotor removal…

1.2 Jaguar XJS Alternator Disassembly

So here it is – your good old alternator. Genuine Bosch, not Chinese replica. Now the difficult bit – disassembly. You need to remove the pulley – by undoing M16x1.5 (also known as M16 fine thread) half-nut. Unless you’re really stupid like I was – you will use a blow torch, give it few whacks with a hammer and struggle with breaker bar until your muscles will become to shake. That includes your arms and legs.

In this place – again – I strongly recommend the best investment for the XJS owner – Cordless Impact Wrench.

With aforementioned hardware – aforementioned nut is a joke. Now you can remove the pulley – it should go off easily unless your alternator was assembles on the weekend shift. Then you need to use your problem-solving skills or pulley puller like the one on the photo below (£15 with delivery)

Right below the pulley is a fan disc which is some sort of over-engineered example of German thinking. There is a groove for the key, but the key is not present since factory. Anyway, the disc will drop-off without any struggling (psst! Just turn the alternator upside down).

You will see four 30+ years old pan-head, recessed Philips M5 bolts and 4 screws in the area of the rotor. Pour those with aforementioned Liquid Wrench (or WD-40-shit if you’re on budget). Recessed Philips bolt are your worst enemy – just turn the alternator and you will see that those 4 are going through the entire length of the housing to finally protrude in the back approx. half inch. Grab a drill and wire brush and clean those protruding ends as deep as possible – if you won’t those will trash the threading inside of the housing with first attempt to udo, best way to avoid it is to run thread die over those ends twice` (I used Bosch GRO, superior to Dremel). Whack the alternator body in the bolt-protruding sections. Place the alternator on the back and pour Liquid Wrench (or WD40 if you wish to be less successful) into the gaps for between the both parts of the housing (where the shanks of the bolts are slightly visible. Wait a while or even overnight if your old and tired. Then, spray everything with LW again…

The final round – you have two options:

1.     You can grab aforementioned Cordless Impact Wrench, hex bit holder and box of Dewalt jobber pozi bits (box, not one). Set the wrench to screw-down mode, press the bit firmly against the Philips (NOT Pozi – now you get it?) pan head recessed bolt and give it 1-2 seconds of whack action. Then put in reverse and undo the bolt. Repeat for remaining 3. Remaining small pozi screws around the rotor are no problem (single impact will do).

2.     You can grab your best Philips/Pozi bits ½ inch ratchet or the best chiseldriver. Support it with dozens of “fucks” and “for God’s sakes”, and a blow torch of course (MAPP recommended), ending with cobalt drill scenario and future extraction problems / snapped locking pliers – just a few to name…

You’ve made it!!! Not…

Top part of the housing is pressed in and is being held by the OD of main bearing. Most of those will come out just with pry action (there are four slots designed for it – don’t break it, it’s aluminium) of the solid flat screwdriver (chisel driver). Unfortunately, there is a big chance of struggle. That’s why the God gave us… SLIDE HAMMER! (anywhere between £15 and £250). You can also grab top housing with standard puller, or hammer it out in old-school way - but it’s more time consuming.

With the set above (£32 with delivery) you will complete most of the DIY jobs effortlessly. Including your XJS stuff. It’s entirely made in China. There is more. They knew, they saw it coming, not sure how, but they’ knew I’m going to buy it. Somehow the slide hammer and all the attachments in the set above are having M16x1.5 thread machined. That’s right – same as your alternator’s rotor. That makes separation of the rotor from remaining part of the housing even more simplified. Just screw down hub puller into rotor from one side and then slide hammer from the other. Bang! Job done without any damage.

So, you’re ending up with:

1.     Alternator Pulley and main nut + wave washer

2.     Top housing

3.     Rotor with bearings, pressed spacer and securing shim (shim to be discussed below)

4.     Bottom housing with stator, rectifier (also know as a bridge)

5.     (removed capacitor and voltage regulator somewhere on the shelf)

1.3 Alternator Bearings – Removal

Now you can inspect your rotor and condition of the bearings. If you’re extremely unlucky - rear bearing is still stuck in the part of the housing holding stator and the rest (chances are 10 to 2300 - as it was taking 5 days to manufacture 2300 alternators and then weekend shift was taking over, manufacturing 10). Especially if it’s burned-off like the one on the photo below:

To remove main (big) bearing you need to use puller. My puller costs £23 with delivery and is able to access tiny clearances. Your puller probably won’t.

To resolve problem with inappropriate tools use screwdriver or chiseldriver to bend that useless shim securing the main bearing to the top housing to gain puller foot access. Alternatively, you can do this:

-       Cut the outer ring of the bearing with angle grinder/Dremel, or crush in the vise – whichever fits you your workshop.

-       Cut the inner ring, don’t worry about the scratches on the shaft.

-       Don’t cut the spacer located on top of the main (big) bearing – reclaim it! (yes AS-PL have those as well, but simply don’t…)



Rear bearing removal is a child’s play, again you can use a hook from slide hammer.

1.4 Alternator’s Rotor: Slip Ring Removal

This task is most entertaining and virtually requires no skills. All you need is a Dremel to cut old slip ring from both sides along the width, pry it open with flat screwdriver, place it on the bench. Now use a butane gas torch (or MAPP or your favourite cigar lighter) to heat the soldering points while slightly pulling the half ring away. Don’t damage/cut the wires soldered to slip rings. Actually, I’m taking it back – it requires some skills.

Chapter 2: Jaguar XJS Alternator Checks with Multimeter

Starting from most relevant facts. You shouldn’t be here if you don’t know how to check disassembled components. Leave now. Alternatively, there are hundreds of YouTube video guides to follow – same rules apply to each one made up to 2012ish. After that you will find ECU controlled in some cars and most will have free-wheeling pulley.

Components to be mandatory checked:

-       Rotor winding

-       Stator winding

-       Rectifier’s diodes

The voltage regulator should be checked only if you just purchased alternator from unknown source or it was confirmed faulty – however all the checks above are showing no faults.

The capacitor does not need checks – I recommend replacing it every time you’re doing some works on alternator (£2)

Using occasion – you may also check if your alternator was repaired in the past. Irregular soldering points between stator and rectifier terminals may confirm that.

If stator or rectifier are confirmed faulty – further disassembly will be required. Stator must be de-soldered and rectifier bolts must e removed. Job done.

Chapter 3: Jaguar XJS Alternator Assembly

I'm a poor man living on social benefits. Like millions of foreigners in UK my budget is estimated by UK Government’s generosity and varies between £5k to £7k of financial aid per month. With current, unacceptable living costs, that leaves me only £1.7k for tools, restoration and consumables each month. That doesn’t mean that my guides are made for poor people - you will need some money to assemble your alternator flawlessly…



3.1 Alternator internal cleaning

Don’t bother with internal corrosion, just clean the plastic cup that holds smaller bearing/provides brush access from the regulator.

Housing can be degreased and cleaned or etched. As every Jaguar Lover you will have a bucket with muriatic acid in children’s playroom and bucket with degreaser under your bed – so go for it. Due to general health and safety – just MAKE SURE YOU WON’T MIX THOSE LOCATIONS.

3.2  Alternator Slip Ring soldering

Regardless of what they say – this is easy. There is only one secret to follow: soldering heat transfer.

It is easy to solder two pieces of thin wire, it is easy to heat those up. With typical slip ring – acting like high efficiency heat sink – you 20watt soldering iron may be a little less than you need.

So, forget about soldering iron, even 200watt solder gun won’t help (you will still need it as an aid) You need gas torch with precise tip. MAPP gas is even better – no, not the real one, but this shit used by plumbers (small tip). I used Dremel torch with excellent results.

Start from cleaning the shaft from old slip ring debris. You will find two types of shafts used depending on generation. Older types are having plain shaft (really tight fit), while newer ones are grooved (easy fit).

Clean the ends of the wires and cover with thick layer of solder

Align the slip ring with wires (cut-outs on slip ring with wire ends) and bash it in wit help of deep socket or sleeve combined with hammer. Press the lower wire into the groove on slip ring (solder is soft – force it in). Make sure that the insulation is still on the wires – exposed wire cannot touch the rotor axle.

With the upper (longer) wire – slide metal shim into the wire channel to distance it from the rotor’s axle. Push it, punch it in – doesn’t matter as long as it creates temporary barrier. Now bend the end of wire into slip ring’s solder groove (press it in).

Now you need soldering iron to put some flux-solder in the area where wires are touching copper rings. See? Your solder cools down instantly? I said PUT SOME SOLDER, not solder it… Slip ring will work as massive heat sink – it’s made out of copper and inner fibreglass completely resistant to heat.

When your droplet of solder is already there – fire up your gas torch and start to heat up the ring just in front of the section to be soldered. It will take a while but eventually solder will become liquid, few moments later it will drop into inclusion and stick to it like shit. There is no way you can make cold joint this way. If the excess of solder spills over the slip ring – wipe it off with cloth while fully hot and sand what’s left from it (brushes will do the rest). Repeat the operation for the lower connection. Everything around is heat-resistant, but do not overdose. Grind the excess of solder off.

This operation sounds difficult, but it’s not… assuming you have IQ over 52 and some manual skills (if you know how to damage steel bead from ball bearing accidentally – don’t do it).

After cooling down – cover the wires/soldering points with insulating varnish - just pull out the shim mentioned above from wire channel, check with multimeter if there is no short between slip ring and the shaft, then fill it up to the top on the wire with channel / drip it on the bottom wire connection as well (re-smear everything, just clean it first at least a little…

3.3  Alternator Bearings – Assembly

Final Bit. If you have no practise – fit the big bearing first, the chances of damage the small one will be minimised. If you don’t know already – you can only hit the bearing with designated spacer or sleeve, only in the race being press-fitted:

-       the one that you’re trying to fit onto something (inner)

-       or the one you’re trying to fit into something (outer)

No exceptions, no damage to the seal or cage. One bang and your bearing is shit and will return to bite you in the cock few or few hundred miles after fitting. Waste of time.

While contemplating on what’s above – straighten the bracket (also known as a shim in 3^rd world countries) with pair of mole grips. Visual acceptance will be enough

So big one first, lubricate the shaft with any oil, put the bracket in first, then slide the bearing. Use deep socket or piece of steel pipe.

Best for the job are off-cuts of the steel pipe:

-       for smaller bearing: 5/8” 16Swg (for non-plumbers: 15.88mm OD, 12.64mm ID, so wall thickness 1.63mm) 

-       For bigger bearing: 13/16" 16Swg (for non-plumbers: 20.64mm OD, 17.4mm ID, so 1.63mm wall thickness)

As you probably know these types are extremely rare… NOT. So get yourself a pair. Any length above or equal to average, fully extended US penis will be enough (10cm).

Punch the bearing in slowly as it sets, then use your 65+ years old muscles to finish the job.

Use only SINGLE strikes, make sure you’re no off the inner race.

If you will forget the bracket – it means you’re a wanker. Some people say that this bracket is not required and you can use Loctite instead. They’re usually right, usually. So if you have it in reusable condition – fit it back or use new from AS-PL (the one on the photo is different, but also fits)

Now do the same with the spacer, flat side goes towards the (later on assembled) pulley.

Move to the small bearing, this one is much easier to fit and much easier to damage so put your glasses on, if you need it. Single strikes rule mandatory.

Your rotor is assembled and ready to be fitted.

3.4  Alternator Housing – Final Assembly

Now it’s time to fit everything together. This type of alternator is designed to be pressed together with the action of the four main bolts (now you understand why the bolts are longer than required) – to avoid unskilled butchers using a mallet or hydraulic press. Bolts are also available in automotive stores – brand AS-PL again, slightly shorter than original – symbol ARS0064. Myself and my new best friend – managed to remove the old bolts without damaging them, but we’re simply brilliant – you’re dumb as you’re reading my guide (you may become smarter than me – just click the PayPal button in the top right corner “DONATE”).

You won’t find regular DIN bolts that will fit, you need 118mm M5 bolts which are half-length threaded. Again, good impact wrench is the key to your success and less f-words dropped.

So, smear the bolts with Loctite Stick or copper grease if your wife sliced the budget. I recommend running M5 thread die over the bolts (and the tap inside the housing, if you messed up with undoing those) prior to it - to avoid housing damage.

Put the rotor into the main housing and cover with mating part. Screw the bolts in equally until those will go into recessions, slightly tighten to make the gap between both parts of the housing visually equal. Now screw down on the opposite ends 1-2 turns per each bolt. Everything will go in easily. If the torque required is too high – simply re-check your job. Tighten up on completion, now fit 4 countersunk screws holding the bracket, do not over-tighten. Put the fan disc and pulley back, screw-down with impact wrench or smear with thread locker and use breaker bar and to tighten it up. Your alternator is ready for the next 60k+ miles and won’t let you down - there are two things left on the shelf to fit back into it…

Chapter 4: Alternator renovation – Voltage Regulator and Capacitor

Those two things left at the end. You should buy new capacitor. You may buy new voltage regulator, but the quality of it will be way below the genuine Bosch (unless you’re willing to buy new, genuine one). Regardless of the bull you will hear from the “trusted workshops”, packing cheapest stuff into your banger, charging for the best – cheap voltage regulator may affect the work of the ECU. Frankly, ECU in your Jaguar XJS is not that sensitive (lower the operating voltage of the SMDs/CPUs – higher chance of experiencing problems).

Time to explain the ultimate questions:

Why some types of voltage regulators are having big resistor installed and other types are lacking it? Are those interchangeable?

The answer is – resistor is there to provide your dash control light to shine bright when your voltage regulator will fail critically (f.eg being hit by the police bullet). It closes the circuit of the bulb in the warning light. That’s all.

Are those interchangeable? Sure they are. Genuine Bosch also made two types. Pick which one you want – doesn’t really matter as catastrophic failures are extremely rare, you have over-voltage protection on-board of your XJS and most important - you have voltage gauge on the dash. Unless you’re absolute wanker, you will notice that things are not right…

To test the voltage regulator, you need to… No way I’m going to explain this here – check dozens of YouTube videos explaining this.

So now, when you are certain that your voltage regulator works (or you know it due to the fact that it was just been pulled out from your car without any charging problems). It’s time to change the brushes. Use Dremel (or better version – Bosch GRO) to grind off the tips of soldered wire (“tails”) – each brush will pop out as those are spring loaded (don’t lose the springs). Don’t follow idiotic drilling guides from YouTube, these are an expression of primitive force – be Mr Smart Retard.

Fit the spring on the wire and fit brush into the regulator. Adjust the wire to make brush fit ¼ length in the housing (3/4^th sticking out). Wrap the wire and secure with any adhesive tape (away from the to-be-soldered section).

Now use your advanced soldering skills and coat the wire with solder. Use good solder, not this cheap shit from boot sale, I truly recommend two types one softer, one harder:

-       Softer and highest quality:

-       Harder and suitable for thick wires:

After coating wire, heat up the old solder on the housing of the regulator, until it melts, use drop of fresh solder for better heat transfer, then add much more and heat it up until it fully joins with top regulator shim. Repeat the process for the second brush. That’s all folks!

Chapter 5: Reinstalling Jaguar XJS 3.6 / 4.0 alternator

This is a final moment where you are about to fit everything back hoping that your beauty won’t burst in flames. Before reinstalling your refurbished alternator – there is only one thing worth doing, however completely unnecessary:

Here’s the pulley of your alternator. Usually corroded and ugly. Solution: drown it in the jar of phosphoric acid for a day or two. This part of alternator is coming off as the first one – so you will have plenty of time. Phosphoric acid will dissolve even the deepest corrosion. After taking it out from etching jar, place it in the pot with boiling water, then take it out in disposable gloves and dry. Spray/brush it with etch primer and any top coat (even clear).

Other thing worth mentioning is the main alternator bolt which should be prepared (same as the bracket) to assembly with use of anti-seize compound or simply copper grease. Please skip this step if you’re in the age of 65+ and you are certain that you’ve made the restoration correctly (it will outlast you I’m afraid). If you are rich and can afford yourself an additional cost of £1.20 - buy a new main alternator bolt - it's DIN 931 with exact size: M10 x 140mm, without head you dummy.

This is the end. Attach wires to your alternator and connect negative clamp to the battery. Plenty of sparks and burning sensation on your palm means that you failed to guess which cable goes where…

All that hassle is designed for fun. If you're struggling, having a high/unstable blood pressure and you have no interest in practising your own mechanical skills – just pay someone to do it. You will benefit economy and decrease unemployment…