Lucas 11AC - bad bearings?

A number of years ago I reported a similar effort to nail down an odd noise coming from the area of the alternator. After some time I identified the fan as the culprit. A few of the spot welds holding it together had let go in a row, causing it to vibrate harmonically at certain rpms. It didn’t get to the point where the piece was shifting and wearing into the belt but that was in the offing had additional spot welds broken from metal fatigue. I have a spot welder so it was a simple fix. You can likely confirm this as the cause of your issue by removing the belt and tapping the fan with something hard to see if it rattles.

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That’s a good thought, I’ve seen that too

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The alternator fan rotation is such that it sucks cooling air from the alternator rear side (ie back of car) to the front side

Whilst you are in there dump the jockey pulley. It is a source of noise and performs no real purpose given the way we drive our cars. Jaguar put it there so owners would not need to adjust the belt every few thousand miles.


I didn’t have time to dismantle the alternator or try a full load test, but was able to try grabbing the fan disc at intervals between the fan blades.

At least one segment produced a clicking noise as I wiggled the fan disc fore and aft. Sign of failure? If it’s spot welds I hope the fan is salvageable.

I understand the 11AC shaft is 5/8", so I called the local alternator rebuild shop (who has stacks and stacks of alternators from all eras) to see if he can find me a 5/8" shaft fan with clockwise rotation for cooling. He’s looking now, thinks maybe a Motorola fan blade might do the trick.

Hope he’s got something. Never knew Motorola (if I remember the name he gave correctly) made alternators!


A test for alternator bearings is to hold the alternator in one hand and spin it you should feel no vibrations or hear any noise
Any local alternator shop can fix it up , I sure wouldn’t be sending it away . The fan might be problematic
Remember your not alone out there could launch a rescue

Jim, I did spin it and it felt fine, no roughness, rattling or otherwise. If it turns out the fan is OK, I’ll talk to my local rebuilder to see if there will be any problem getting bearings. I had read other people who had to work hard to get a set of replacements for the 11AC.

The rebuilder found me a fan to fit a 5/8" (.625") shaft (figure taken from the Coolcat website) with straight blades so I presume it’s omnidirectional.

Concerning me is that the spare C24392 alternator pulley I picked up last winter seems to only measure at .57", so I hope I don’t have a duff repro part/incorrect application here.


You need a shop that works on commercial type equipment if you goggle alternator repair they’ll show you how to do it yourself easy
Bearing numbers are standard across manufacturing or they use to be and I really doubt the bearings are anything special
When I was young working on motorcycle cranks I’d change the main bearings .the spec for them was to be within limits for 10 hrs



The rear bearing is more likely to be “custom” than the front, but they’re out there:

I also found a disc-type fan said to be for 65-71 E-types:


But, it doesn’t look like mine as the fins project beyond the fan disc. I’ve never seen one like this on a picture of an 11AC. To be honest, it looks like a 11AC disc welded to a conventional-type angled fan blade.

Now my area rebuilder gave me a fan for a 5/8" (.625") shaft. It’s a conventional type and turned out to have angled blades. I believe this is for clockwise rotation if I’m correct that the blades should be angled towards the direction of rotation for the alternator.

It looks almost brand new other than a light coating of dust, the rebuilder said he had a stack of them back on the shelves!

I also matched it up with the reproduction C24392 pulley and the pulley is definetly undersized. The fan came out around .622-.623". The pulley - .585-588". The rebuilder trial fitted it to a 5/8" shaft and it didn’t fit of course. Here’s where I overlaid the two pieces:

So most likely I have another duff reproduction part and will have to pay a machine shop to bore it out correctly.


Just get a step drill clamp a piece of metal with a center hole to the back and drill

I may have to give that a try! Thanks.

Especially depending on how much I’d be charged to bore the pulley out correctly.


I was able to remove and dismantle the original 11AC and compare with the reproduction unit.

The reproduction pulley is not as far off as I thought, but it still will not slide onto the alternator shaft of either unit. The old pulley pops on to the new one, and the measured shaft diameters for both units is very close.

Probably it would just take a bit honing to get the new pulley to slide on, but lacking a drill press or other fixture to assure concentricity I’m not sure how I would tackle that. A step drill seems too extreme for such a small clearance, and the diameter of shaft or pulley is not a neat 5/8" (.625") - more like ~.585". Opening the pulley up by maybe .002" might do the job.

As to the real problem - it indeed seems to be the fan so looks like Michael called it. The center keyway for the fan has metal broken off, so likely it was no longer concentric. When I rotated the alternator shaft observing the edge of the fan, it definitely had an eccentric motion visible at the edge of the disc, obscuring the edge of the alternator body as it rotated then revealing it.

The issue is that the fan is scraping the body. Would making sure the fan is centered solve that problem? Note the tips of the fan here:

Then the body of the 11AC and the scraping on the upper left quadrant of the body:

And why the fan isn’t concentric - the fan keyway is damaged. However the rest of the fan is solid - no loose parts or welds, or cracks.

If concentricity is causing the fan interference, I’m not sure how I could fix that. I can’t use the substitute fan from my rebuilder, because note how the Lucas fan is dished in the center. This gives extra clearance for the fan tips, whereas the flat “conventional” fan scrapes the body.

I could flip the fan to use the opposing keyway to the damaged one, but I would need to file it. I don’t think I can use a shim to gain clearance because I think that would also raise the pulley and throw it out of alignment. Given the way the lower mount on the 11AC is designed I don’t see alignment could be done there short of slotting the mount bracket.

Any ideas on how to repair that thin sheet metal keyway? Maybe some TIG welding pro could do it? Or take the easy way out and just file the opposing key and figure it will last until my time on Earth is up? I’d prefer to fix it properly though.


I’d just gas weld it to build it up and file the hole but I have that equipment .your over thinking it it’s just a fan. Tig welding produces a very hard weld

You could cut a keyway into a washer and tack weld it to the fan. That’s about the only way to salvage this. Original counterclockwise fans are hard to find, but you may be able to find a modern 15mm ominidirectional fan somewhere.

I don’t have a gas welder, only a MIG. While it’s always great to have an excuse for a new tool, it takes practice from what I understand to be able to gas weld (especially thin sheet metal.)

If I had the tools to ensure concentricity I’d try the washer trick. I was thinking that a jewelry welder might be a possibility, but I don’t think the under $250USD models will be up to the job (they’re mainly for spot welding and have no filler rod or wire.)

I’ll see if the machine shop I take the pulley to will have any ideas. I would think I can just use the other undamaged keyway so that’s what I’ll do if I want the car on the road ASAP.

I found this batch of Lucas E-type fans on eBay. Alas, the one that matches my fan is the one that’s damaged. :frowning: But maybe I can use one of the others.

Jaguar XKE E-Type Generator Fans - Lot of 4 Pcs | eBay


Thought just came to me - if 15mm fans are very common for Lucas alternators, maybe I could use a fan for some other Lucas model instead. Many seem to have the dished center, which I’m thinking is important to maintain proper pulley alignment?

eBay has many more listings of Lucas alternator fans for other models.


make a jig out off square ply wood with a hole in the centre to line up a washer Use your mig welder to spot weld the washer in 3-4 places then drill , file it out what ever is required

Hmm. That’s not been my experience. I switched from oxyacetylene to MIG for bodywork and found that the MIG welds were indeed much harder and could actually crack when planished so I switched to TIG, either using the same mild steel filler rod as for oxyacetylene or even none at all with a tight fitment between panels. Then again, my oxyacetylene setup isn’t high quality while my TIG is. I’ve actually had less consistent results with gas welding from the flame drifting either way out of neutral.

Update on this saga: I judged that sending the mismanufactured pulley to a machine shop to remedy the fit issue was impractical - too expensive. The shop I visited said they would have to use a special boring bar and then recut the key slot, which would cost more than the pulley.

It turned out I was able to get it to fit with a few passes of a sanding drum. Only .002" or less had to be removed, and I managed to do this without appearing to affect concentricity. But the slot for the Woodruff key (actually a fixed key on the replica) would not fit. I spent a lot of time filing the slot but was worried I was getting it wrong and close to ruining the pulley.

As it turned out, it fit very well on the original 11AC alternator with a rather beat up Woodruff key, so I gave up and put the old pulley on the new replica, and reserved the new pulley for the old 11AC original! Though I plan to fit a new Woodruff key which might not fit as well - I don’t know if the beat up Woodruff key was the cause or the victim of the cooling fan damaged keyslot.

Anyway, not having been able to find a reasonable replacement fan yet, I put the old fan back on, but used the undamaged key slot opposite of the damaged one. Was it Lucas foresight that supplied a duplicate slot on the fan?

After install, it fired up and seemed to work well, but when I revved the motor above 2000 or so I heard a rattling sound. Uh-oh. I decided to take the time to try to be scientific about it, and took the fan off, then re-installed the assembly.

No rattling sound. Well, I don’t have a spare fan, though Martin Robey lists a reproduction Lucas 11AC fan that looks like a match for my old one. There was no scraping on the alternator, and no blades are loose. So why it is rattling?

But then I remembered that the SNG Barratt repro alternator had this rubber O-ring whose function I didn’t understand. I originally slid it to the base of the alternator shaft, where it was duly crushed by the fan/pulley assembly and probably wasn’t where it was supposed to go.

But what if it was supposed to go between the pulley and the fan surface? So I got another spare O-ring and put it between the pulley and the fan. I tightened it up and reinstalled.

So far - no rattling at 2-3,000+. I don’t know if the O-ring actually had an impact or not. But if this will hold up for a thousand miles at least, I can salvage the driving season. The Robey fan, even if in stock, might not get to me before it’s time to put the Jag away.

Let’s see if I can get a few hundred miles on this and I’ll report back on how it and the repro alternator are holding up.


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