Alternator magic smoke

[Blaster]

After my failed attempt to blow the cobwebs off the Lotus last month due to a large amount of smoke escaping from the alternator.

I needed a new battery so once it was connected I attempted to start the car with the immobiliser on to get oil pressure up but the solenoid just went click. I put a jump pack on and it turned over no problem and oil pressure was seen.

I took the immobiliser off and she started but the volt meter was showing 16V, I turned the engine off and checked all the earths. and re started and this time it showed 13.5 volts so I let it run for 5 minutes.

when I tuned the engine off a lot of magic smoke appeared. On dismantling the alternator thinking I would have to replace the module this is what I found.

Alternator.jpg

My local rebuilder has quoted about £250 to rewind and refurbish it.

I am confused as to the replacement as the SJ one is not suitable for the O2 equipped cars.

The only Lotus part number I can find is A100E6029S but does not say it is suitable for O2 equipped cars. This part number is also on Exige and Esprit.

So the question is will this part work with my closed loop M100?

[dapinky]

Tony,

I took a risk and bought one for an Impulse from Rock Auto - and it is fine (Trevor B also used the same one without issue)........

....... https://www.rockauto.com/en/moreinfo.ph ... 2412&jsn=3

It is currently more expensive than when I got mine, but still a good price, even with shipping.

Be aware, it is a few mm larger than the Lotus one, but will fit without too much swearing to get it in the gap (I did mine witht he suspension out and it fitted easily - you *may* need to fiddle a bit if you don't want to remove extra parts.

It comes with a bigger pulley, but works fine - with a slightly longer belt (which I got in the UK). Can't remember the size of belt, but will look it up if you want to go this route.

I also still have the seized alternator that I took out of mine if you want to cannibalise it for parts.... I can either post it to you now, or bring it to Castle combe for you to fiddle with at your leisure so you will have a (potentially) spare.

[Blaster]

Thanks Dave.

Should be here to fit over Easter.

It would be great if you could bring the seized one as it is always worth having a spare.

[Tuga2112]

i take it you dont need any more help then ?

[Blaster]

The problem with leaving the bigger pulley on is that it is possible to over rev the alternator.

A friend of mine had a rally prepared Imp that would rev to 12000 and if you missed a gear it would either throw the belt off or the armature would turn into a birds ness. The engine would survive but needed the valve guides changing ever 3000 miles.

[Blaster]

i take it you dont need any more help then ?

No I have ordered from rock auto. Will find out how easy it is to get back in being slightly bigger over the bank holiday. I need to do an oil change so will change the filter while the alternator is out of the way.

Thanks for getting back to me.

[Tuga2112]

i take it you dont need any more help then ?

No I have ordered from rock auto. Will find out how easy it is to get back in being slightly bigger over the bank holiday. I need to do an oil change so will change the filter while the alternator is out of the way.

Thanks for getting back to me.

only suggestion i have is removing the subframe and going there from underneath
in my experience is faster... the subframe is a rather straighforward one to remove even tho it sounds excessive

[dapinky]

Tony, the larger pulley will under rev, not over rev....... I can't remember the calculations (it's on my project thread), but lets assume that the new circumference is 200mm, and the OE one is 150mm....... for every 200mm that the belt travels, the new alternator will turn once, whereas the old one would turn 1.33 revs.

my concern was that the alternator at idle wouldn't generate enough electricity to extinguish the dash light, but a few calculations and research allayed my fears, otherwise I would have simply swapped the pully from the old one.

Edit:- this is the relevant post with the pictures and calculations...... viewtopic.php?f=79&t=29457&p=375911&hilit=alternator+belt#p375911

..... and the new drive belt I fitted was a 4PK713 (original was 4PK690) - https://www.ebay.co.uk/itm/165176893432

[Blaster]

The alternator arrived today and is in loosely bolted up, I had to remove the bolt from the engine mount and lower then engine to get it in. The new one uses aluminum foil around the electrics and is as soft as the kitchen stuff.

I defiantly need a new belt as the one on it is 4PK675. I am going to get the 713 one you suggested Dave but it also needs to be longer as the centres are going to be further apart due to the larger diameter.

[dapinky]

Tony,

I tried a few different sizes (sort of!) - in so much as I positioned the alternator where I wanted it to sit when it's all together, then used a bit of rope to see how much longer the belt needed to be...... but that wasn't accurate, so I cut the old 675 belt and elongated it with gaffer tape and then measured the gap and did the maths!

It was still a bit of a guestimate, and I decided that anything between 710 and 720 would be good, so it was just finding one on ebay in that range, and a 713 was up for a fiver (715 is also quite a common size apparently).

When installed, the alternator was perfectly in the right place to be able to get to the bolts from the top to tension the belt without anything being too much in the way to make it work.

[Tuga2112]

When installed, the alternator was perfectly in the right place to be able to get to the bolts from the top to tension the belt without anything being too much in the way to make it work.

in my experience, this was the most valuable part of using the longer belt that Dave suggested. it made subsequent work (which unfortunately happened more than once thanks to SJ's parts quality) considerably easier

[NoahR]

Blaster, did the new alternator from RA and the correct size belt all work well in the end, then? - With closed loop.

[Blaster]

Blaster, did the new alternator from RA and the correct size belt all work well in the end, then? - With closed loop.

Yes it all worked. The alternator from Rock was larger so I had to release the engine mount and raise then engine to get it in. I used my pully from the old alternator and used the longer belt recommended by Dave. The cover for the regulator on the new one is made of foil, by then time I had it in place is was dented.

[NoahR]

Interesting, thanks.

Removing the engine mount bolts took me hours last time, just due to the access, but perhaps I'll have the technique dialled this time, haha.

Just to confirm, you didn't need to swap the regulator - it worked out of the box?

[Blaster]

Interesting, thanks.

Removing the engine mount bolts took me hours last time, just due to the access, but perhaps I'll have the technique dialled this time, haha.

Just to confirm, you didn't need to swap the regulator - it worked out of the box?

Yes the rock auto one worked with the O2 sensor once squeezed in.