Megane alternator pulley

I have an X-reg Renault Megane (1.6L 16V).

yesterday I had to stop when the battery warning light came on. Opening the bonnet, it turned out that the pulley had detached itself from the alternator, and was lying at the side. The friendly breakdown chap said it wasn't meant to come apart, and a new alternator was called for.

I don't like to doubt his word, but since the alternator spindle and the inside of the pulley (well, the black sleeve inside the pulley) are threaded, it looks very like they are made separately and just screw together.

I got myself a copy of Haynes, hoping for a fully expanded diagram (as there had been in the old Volvo manual I had a few years back), but no.

So the question is : should it be a simple job to reattach the pulley to the alternator, or is it indeed knackered ?

The outside of the black sleeve has a large hexagonal insert, sugesting that an enormous (3cm) allan key be used to tighten it - how do I lock the alternator while tighening it. OTOH, there seems to be the impression of a washer at the base of the hexagonal inset, suggesting perhaps an additional nut holding the pulley to the alternator. There's a diagram in Haynes : 1A.18.18a, but it's hard to tell from that :-(

Oh - car has AC and PAS - I believe that affects the layout of the alternator belt.

TIA in advance for any suggestions.

dd

Reply to
Dave Denholm
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What make is the alternator.

Reply to
John

Just guessing as your description doesn't ring any bells, and I would expect the alternator itself to be perfectly OK, once the pulley is re-attached.

From what you say, it would appear that the pulley screws onto the alternator shaft, and is then locked with a nut and washer. If that is the case, if the pulley screws freely onto the shaft, it can be held while you tighten the nut. After buying one of course. The original one could be anywhere. :-) OTOH if the pulley is tight, you might have to strip the alternator, and hold the armature in a vice or grip it somehow, (using some sort of padding) in order to screw the pulley on. I would suggest you use Loctite when you assemble it. Either 'Screwlock' or preferably 'Loctite Retainer' Assembled properly with Retainer, it would never come apart again. At least not without heat. 200-300 degrees C. Mike.

Reply to
Mike G

To answer John's question : I don't know the make of the alternator. As far as I know, it's the original one fitted. I couldn't see any obvious manufacturer mark. I did various web searches, but didn't find anything.

Indeed - I have every reason to hope the alternator itself is okay. (It would be particularly annoying to buy a new alternator and find that it doesn't come with the pulley attached !)

A little more research : I measured the alternator spindle and the shaft of the pulley, and it looks like the thread of the alternator would not emerge out of the pulley. ie there would not be a thread exposed to which to attach a lock nut.

However, the alternator spindle is hollow, and so in theory it would be possible for there to be a bolt to go through the pulley and then inside the alternator spindle. I couldn't see a thread inside the alternator spindle, but I couldn't see very far inside. I'll have another look tonight.

Sounds a good idea if I get it right first time, but could be nasty otherwise :-(

dd

Reply to
Dave Denholm

Seeing as the shaft is too short for a nut, I think the hole in the shaft must be tapped for a screw and washer. Explains the washer impression on the pulley.

Which way does the alternator rotate? When facing the pulley.

Been thinking about why the pulley came off. If it rotates clockwise, and if the thread on the outside of the alternator shaft, and (tapped hole?) are both r/h threads, even if it came loose, the chances are that it would stay on. OTOH if it rotates anticlockwise, and if the central screw became loose, it's just about certain the pulley would soomer or later come off. Certainly sounds like that's what happened to your Megane. Vice versa of course if the threads are l/h and the alternator rotation is anticlockwise. I,e The ideal would be r/h threads for clockwise rotation, and l/h threads for anticlockwise rotation. Mike.

Reply to
Mike G

The reason I asked the make is because a lot of Bosch alternators now have a slip pully which regularly fall apart and leave just the center of the clutch attached to the shaft. If this is what's happened, you'll need a special tool to remove it, or else strip the alternator and hold the rotor in the vise. Both jobs for an autoelectrician. Try your local autoelec. If this is the problem it should be possible to just replace the pully.

John

Reply to
John

It is a Bosch, and this might explain why there seem to be more pieces would have appeared necessary. I had been wondering why there was the inner sleeve which moved relative to the pulley. (There does also seem to be a black outer sleeve bonded to the inside of the pulley.)

But in this case, the whole thing has come off the alternator.

I think for my own peace of mind, I'm just going to replace the alternator : even if I did get the pulley back on, I'd probably never have complete confidence that it wouldn't just come apart again, at the least convenient time.

thanks

dd

Reply to
Dave Denholm

Don't know : I never had a reason to look at it before it broke.

I'm guessing clockwise, since the Haynes manual says to turn the crankshaft clockwise when making other adjustments, and the belt is such that the alterator would turn clockwise if the engine's turning that way.

That was my thinking too. The action of the belt should tend to keep the pulley attached.

But I would have hoped that one of the designers would have spotted this flaw early on ..?

Only possible idea I can think of is that for some reason, the drive via the pulley and the electrical load both relaxed, such that the momentum of the alternator kept it rotating faster than the pulley for long enough to detach the loosened pulley. (ie both were rotating clockwise, but the alternator was rotating faster than the pulley.)

But it sounds rather far-fetched.

dd

Reply to
Dave Denholm

Doesn't have a woodruff key to hold it together by any chance? Just a thought.

Reply to
Taz

Not necessarily a flaw. No doubt the same basic alternator is used on different cars. They may have decided that fitted tightly, and maybe using a thread sealant like Loctite, the same shaft could be used regardles of direction of rotation

I think you're right. :-)

Mike.

Reply to
Mike G

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