The "direct replacement" alternator that isn't, but seems to work after you modify everything ;-)

Hello Folks -

Let me start by saying I got this to work - so there is that, and generally speaking it wasn’t overly tough, but nonetheless annoying - lets go through it:

I needed to replace the alternator on my '70 2+2 A/C + P/S, and discovered there are few options out there, aside from the comparatively expensive re-manufactured Lucas unit. One of those options is a WOSP performance alternator (available from one of the more common part sources - not sure if you’re allowed to say which specifically). This alternator is advertised as a quote “bolt-in replacement for an original”, making 70 amps and internally regulated - so far so good. The only issue of course is that this alternator was a “direct bolt in replacement” in the same way that Santa is a 120 lb clean-shaven athlete from Guam.

  1. The fan is incorrect - being standard rotation versus reverse. Alternators don’t really care which direction they turn, alternator fans however, generally do. For a 2+2 with the high-mounted reverse position alternator, you need a fan that works while rotating counterclockwise. FIX: Multiple options, including a reverse rotation fan that will fit the alternator shaft, but in my case, I just used the fan from my Lucas unit. Does it really fit?…no. It is close though, so I used a dremel tool to widen the hole. The shaft on the lucas unit uses a key-way to keep the fan from slipping, the WOSP unit does not - it just relies on the clamping force of the nut and spring washer - so no need to worry about the keyway notch in the fan.

  2. The pulley is out of alignment with the water pump pulley Obviously, you need the pulleys to line up so that the belt can do its job. You also need to make sure the fan doesn’t foul on the water pump pulley. The stock pulley has sort of a neck to it, the WSOP pulley doesn’t, so its basically too short. The stock pulley will not fit on the WOSP shaft, so you must use the WOSP pulley. The WOSP unit comes with two washers under the fan, then the fan, then four washers, then the pulley and lock nut - but this won’t line up or allow the stock fan (now fitted) to clear the W/P. What worked: No washers under the fan, then a 1/4 inch spacer and two washers (if I recall), then the pulley. I happened to have a spacer the right size, another four washers would also have worked. This allows the fan to be back far enough (toward the body of the alt) to clear the W/P pulley, while allowing the alternator pulley to be out far enough to line up with the W/P pulley groove. The locknut will engage all but perhaps two of its threads, and its a decent sized nut, so just be sure its tight, don’t forget the cupped spring washer, and perhaps add some blue loctite.

  3. The wires are too big The two larger alternator wires have some pretty wide connectors, too wide in fact to fit into the back of the WOSP alternator. Ok…ok… I lied. They do fit, but with such tight tolerances that there is a fair chance you’d be striking a welding arc the whole time…way, way to close for comfort and the stock rubber isolators wont fit - there’s just not enough room and I’d be concerned they’d wear through, and then you’re back to welding. Both wires connect to the B spade connectors, but fortunately, WOSP also provides an actual B post in addition to the spade connectors. What worked: You need to transfer your stock copper connectors from the Lucas unit to the post on the WOSP unit - which sounds easy enough (see item 4). This of course is a much bigger issue if you don’t have a stock unit to take apart.

  4. Naturally, the B posts are different sizes The post on the Lucas unit has a smaller diameter than that of the WOSP unit. You’ll need to enlarge the hole in both copper connectors. Dremel worked well here. Be sure to retain the black rubber isolator on the WOSP unit and the washer, the copper connectors should not be in contact with the body of the alternator.

  5. The spacer / bushing in the alternator mounting hole is too long. While the alternator has the right mounting holes and fits the bracket, the spacer / bushing in the forward hole is too long. The net result is that the mounting bolt only shows about half the threads it should once pushed through the bracket. Options include a longer bolt, replacing the WOSP bushing with the stock bushing, or reducing the length of the bushing. What Worked: I actually didn’t do any of those things. In the stock configuration it goes Bolt > Washer > thick spacer> through bushing, alternator and bracket > nylon locknut. With the bushing being longer, I just removed the thick spacer, problem solved. I’m sure someone will tell me that the spacer I removed is a special shock-absorbing poly-mimetic alloy, that in addition to being a killing machine from the future, is also a critical Jaguar-only spacer…but…until that happens…I removed it…no ill effects.

  6. Wiring Woes. There are several easy wiring alterations that need to be made, and the instructions do a good job of telling you what they are, while doing absolutely no job whatsoever of telling you exactly where to find said wires. For example, the manual tells you to disconnect the ground from relay 6RA - but neglects to tell you that there are several such relays, all the same place, none of which have wires labeled “remove me for WOSP installation”. What Worked For starters, on my car anyway, the 6RA relay you want is the lowest relay, to the left of the battery. This should have a white wire with a red stripe, right in the middle. The wire you want to disconnect is the ground, which is at the top of the relay, single spade connector on its own. The relay is also marked, though you’ll probably need to clean it off to see, but each spade connector has a code: W1, W2, C1, C2 - you want to disconnect W1. I can’t take credit for this info - I did a google search trying to figure out which wire to pull off, and data from @ Michael_Frank popped up with everything I needed - so thank you sir. Here it is for anyone else looking for detail on the charging system:

The 3AW relay is taken out of the circuit entirely - you remove ground, and connect the remaining two wires together. Ground is the thinnest black wire - I traced one wire back down to the wiring harness that goes to the dash (so to the ignition light) and the other middle wire is a pretty thick signal wire - that left the thinnest black wire as ground. I removed said wire from 3AW, then connected the other two wires together (I turned one into a male spade connector and simply connected that to the existing female spade connector of the other wire).

You also should (optional) disconnect the ground from the 4TR voltage regulator (middle spade connector on mine).

Lastly, the two field wires are not used with the WOSP unit, so you just remove or isolate them. You do use the small signal wire, and there is a spade connector for that on the WOSP unit.

In all cases, I disconnected and isolated wires, rather than cutting them - just in case I (or a future owner) ever wanted to go back to a Lucas alternator.

  1. Don’t let your nuts get whacked. The bolt, and specifically the nut, provided for locking belt tension at the top of the alternator is a little big. When fitted, the nut will clear the stock Lucas fan, but just - 1/16th of an inch stuff in some cases (depending on how straight your fan is). This was too close for me, so I reused the stock lock-nut, which was still 1/2 inch but had a smaller over all body size, and provided more like 1/8th inch minimal clearance.

The alternator works great best as I can tell, charging well and although I’ve not had it under any stress or miles, so far its doing all the things you’d expect.



Like some other items… you don’t so much ‘get a part’ as you ‘get a kit to make the part’.


Funny, funny description! A+!


What is, “WOSP?”

What a nightmare!!
On your A/C car, the alternator is a rather robust piece of equipment. I just had mine rebuilt, and it will outlive me.

The good thing about getting older is that time goes by faster, and under current circumstances, that is good.
LLoyd Nolan, June, or maybe July 2020

I strive to live my whole life with this philosophy. With a couple not-too-serious-but-still-painful exceptions, so far so good.

OK… thanks. Sorta answers the question.


I kept the Lucas unit, just in case, but I’m not sure there’s a rebuilder near that can do it, besides, I had some questions about the condition of the regulator and 3AW relay, so this single change fixed three potential issues.

@Ahwahnee : I’ve never met a “bolt in kit” that actually was…ever :smile:

@Jcrosby Me too, though kids and a 65lb lap dog serve to undermine my attempts.

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Its the same case with the direct replacement for the B.U.T.E.C. alternator for S3 cars. The following picture shows the adjustment bracket supplied with the replacement Alternator offered by the usuals. That bracket is close to nothing on the engine without conjuring up some “Heath Robinson” contraption.

The following picture show my manufactured solution, which uses the same principle as the original and part of the original tensioning device.

and the following picture, the assembly.



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Nice, they look identical.

Very nice. It always amazes me when you get something, built and advertised for your specific car, with mounting parts that have absolutely no home, place or possible useful location. It seems to me that I more often use said parts to modify the mounts of the next supposed “bolt-in” part. Perhaps that’s the idea?..You get the mounts you need for the prior part, by ordering the next? Marketing wizardry.

Or designers (cough) as thick as two short planks, dipped in porridge and stuck together.



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My FAVORITE one was–and this’ll crack you up!!

“Bolt-on headers.”


Oh, s#!t, I glued mine… image

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The truth here is that when it comes to alternators, manufacturers make do with available parts, as making custom castings makes no sense for small production runs. Your first clue should have been that it’s “internally regulated”. This is fine, but it tells you that the wiring is going to be non-standard right off the bat. And the rest is inevitable. This is why I post DIY faqs rather than offering kits.

For your fan, over time you may discover the reason that the Lucas fan was keyed. It’s not designed for a friction fit and unless you really wail into the nut (which risks the rotor shaft), it can loosen up on you. Listen for a slight rattle, and be quick with the wrench if it acts up. There is a Bosch fan listed in my Bosch conversion faq that should work for you if your fan self-destructs. There’s also a lightweight Prestolite fan listed there, but that may be harder to source.

Your alternator relay is in the wrong place…it should be the second from the top. Once the relay is disabled, you can leave the harness on the 4TR just for show, as it will be completely powered down.

The good news is that an alternator is an alternator is an alternator. Once you have it in place, wired up and aligned, it should work for a very long time.

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Just to play Devil’s Advocate here…

How much more was a re-manufactured Lucas brand alternator? What was your time and aggravation worth to make the one-size-fits-many solution actually work?

Personally, I love to update/upgrade my toys. All of my pre-1970 tractors have been modified to alternators with separate regulators.

How’s your 20/20 hindsight on this project?

I have stated in the past many times here. The original Lucas alternator on my new A/C equipped car never could keep up in stop and go traffic with accessories on. The same was true for my father’s car a 69. In the mid-seventies purchased a Lucas factory rebuilt to have a spare, it also could not keep up. These were 60 amp rated. I am now using a Lucas Eletrik clone rated at 55 amp that was a replacement for a Massey Fergunson tractor.
No longer have to be concerned about the needle in the red, it is smaller and has a built-in regulator. I also purchased a similar one as a spare. The Lucas Eletrik one is no longer


So “Worth it!” and “Totally necessary.”

I grok.

@E_NEW I’m down with devil’s advocate. Short version - hindsight is, I’d do it again. Here is the calculus:

  1. The WOSP unit was $307 to my door. The re-manufactured Lucas would have been $570 ( I would not have surrendered my core, either)

  2. The reasons for changing the alternator were several, but some symptoms also pointed to a potential regulator issue - So plan was to change that (would have been $60 to the door) and possibly a temperamental 3AW relay ($65 to the door)

Collectively, going the Re-manufactured route would have been $700 +/- . Comparatively, the WOSP unit, extra work and all, cost only its initial $307, and due to its more modern design, eliminated both the external regulator and A3W unit , while preserving functionality. It also charges significantly better, rated at 70 AMPs.

It may also be worth noting that even the advertised re-manufactured units had clearly differentiated electrical connections, so there is no guarantee it would have dropped in without modifications anyway.

@Michael_Frank I quite agree, that there were many clues that some work would be required, and in fact expected. That said, something advertised as “a direct replacement for stock” should not fry itself due to lack of cooling, shred its belt due to significant pulley misalignment and create electrical arcing so severe as to probably burn your car to the ground - If in fact it were just bolted on, as suggested by the marketing material. :face_with_raised_eyebrow:

When you go into a conversion away from stock, using whatever parts you find off the shelf that look “close and might work” all of the above and more are on the table from the start. When you buy a part that is specifically noted as a direct stock replacement however, I think the expectation should be more reasonably in line with a tweak here, adjustment there, as opposed to redesigning the unit. :grinning:

The cost of my Lucas Eletrik originally was $90. Original spec was quoted 60 amp but was 55 amp. Instead of exchange they said to just keep it and will refund. My cost $0.
My other back-up alternator was $60. I did have to pay for a new pulley and fan for both.