The convention seems to be that that when fitting an alternator, the output cable should be routed similarly to the former dynamo. A control box terminal is used to join to the existing cable to the starter terminal that is connected to the battery.
Since I have the engine and gearbox sitting on a pallet, it would be very tidy and easy to fit a cable direct from the B+ terminal and around the cowling to the starter. I think I would be well advised to sleeve the cable and I would be clipping it to the cowling at regular intervals.
Has anyone done this and what cable size should I use/ I am debating between 5mm and 6mm but for flexibility I don't want it unnecessarily thick.

fiat500 said:

The convention seems to be that that when fitting an alternator, the output cable should be routed similarly to the former dynamo. A control box terminal is used to join to the existing cable to the starter terminal that is connected to the battery.
Since I have the engine and gearbox sitting on a pallet, it would be very tidy and easy to fit a cable direct from the B+ terminal and around the cowling to the starter. I think I would be well advised to sleeve the cable and I would be clipping it to the cowling at regular intervals.
Has anyone done this and what cable size should I use/ I am debating between 5mm and 6mm but for flexibility I don't want it unnecessarily thick.

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6mm would be ample. You could get yourself a couple of metres of 6mm twin and earth from your local electrical suppliers. Strip it down and take the brown out and fit some crimps on it.

How quick do you need it? I have all the cable, crimps, crimper and could make up a lead for you and stick it in the post. What do you need an eyelet on each end? If you want me to let me know how long you need it.

Vitesse said:

If you want me to let me know how long you need it.

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Thanks Tony, you are a kind and generous, genius electrician.
I might take you up on that but you've given me excellent advice there.
I was thinking I would have to buy a roll of multi-strand cable but because of the way I plan to do this, the standard, solid core cable might actually be a better bet as there is going to be a fixed run with no flexing.
I am pretty sure that I have a bit of 6mm in the garage attic and will dig around tomorrow.
I am hoping to get the "operation" done pretty promptly now as apart from the wiring side of things everything else is in place. I have even put Murf's original distributor back in so that I have the 123 ready for the bigger engine.
I prefer the performance on the standard distributor...maybe the advance springs are worn but there is just enough more lively performance to make me wonder slightly, "why am I doing this?":bang:

Be aware that twin and earth cable i s solid cored and not ideally suitable for crimping - stranded cable is best for this application as it is far more flexible.
6mm is ample.

fiat500 said:

Thanks Tony, you are a kind and generous, genius electrician.
I might take you up on that but you've given me excellent advice there.
I was thinking I would have to buy a roll of multi-strand cable but because of the way I plan to do this, the standard, solid core cable might actually be a better bet as there is going to be a fixed run with no flexing.
I am pretty sure that I have a bit of 6mm in the garage attic and will dig around tomorrow.
I am hoping to get the "operation" done pretty promptly now as apart from the wiring side of things everything else is in place. I have even put Murf's original distributor back in so that I have the 123 ready for the bigger engine.
I prefer the performance on the standard distributor...maybe the advance springs are worn but there is just enough more lively performance to make me wonder slightly, "why am I doing this?":bang:

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If you have any 10mm T&A knocking about that is multistranded or 6mm SWA is multistranded as well.

Vitesse said:

If you have any 10mm T&A knocking about that is multistranded or 6mm SWA is multistranded as well.

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Don't worry Tony, I'll get it right. If I end up with solid-core it won't be subject to flexing and I will solder the terminals even if I use multistrand.
I want yo get some heat resistant sleeving anyway so I have the opportunity to shop around if needed. As you say, its only a couple of metres, if that.
Obviously I will keep you posted and I'm busy building a bathroom the next few days anyway.:bang:

I now have all the components needed to do this job but now realise that what I am proposing has a limitation that I hadn't anticipated. On later models, the main feed to the fusebox is supplied from terminal 30 on the control. So if I do route the alternator output direct to the starter terminal, I would still need to route another cable back in the direction of the control-box to connect to the fusebox feed cable.
It appears that earlier cars took the main feed to the fusebox direct from the battery terminal. I always wondered why the replacement main cable that I bought had an additional, much smaller gauge cable spliced in at the battery post connector.
It makes sense to me to use that direct battery connection to run a fusebox feed direct from the battery along the existing cabling route behind the fuel tank. It may only be a minor advantage but it slightly reduces the potential for voltage drop and possibly for fire. The wiring-loom in the car is the original and this means that this most heavily loaded cable will be brand new.
None of the existing cabling will be modified so it will be easy to convert back to dynamo use.

I am a bit confused why don't you just use the existing brown wire in the loom down to the starter from the control box? If you put an additional wire in, your just going to end up with an unused wire flapping around (slight exaggeration but you know what I mean) unless I am missing something?

All you have to do is move the B+ wire terminal 51 to connect to the same terminal as the starter wire. Easy to reverse out? Are you going to use a gutted VR or have you come up with some modern solution now you have tempted down the modding path.

Vitesse said:

or have you come up with some modern solution now you have tempted down the modding path.

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Obviously I have gone down the modding route.

There are two things that are guiding my thoughts.
1. The alternator potentially has an output which is greater than that of the dynamo. Whilst even Mattsdad, sort of guardedly implies that the existing control box output cabling is within practical tolerances for that, I will be happier to see a thicker cable gauge all the way to the starter where it meets the battery feed cable.
2. I would prefer to avoid cable joins and connector blocks. I especially don't like the idea of using the old control-box as a facsimile of its former self; I would prefer to remove it and store it carefully off the car. In any case I am currently using the electronic one.

So my idea is actually quite simple and streamilined although it does mean that I will have a few temporarily redundant cables which will be neatly stowed.

The layout is:
a. 6mm cable from the B+ alternator post, in heat resistant sheathing clipped to the back of the engine cowling direct to the starter terminal.
b. The existing dynamo "F" cable used to connect the ignition warning light to the alternator.
c. A new 5 or 6mm cable direct from the battery + post (using an existing factory-fitted connection) to terminal 30 on the fusebox and the existing feed from the starter terminal becomes redundant.

It might sound unnecessarily complex and obtuse but I feel that it actually simplifies the wiring and as I said previously, voltage drop and opportunities for short-circuits will be reduced....safer and more reliable.

Hello I am new here
Here are some to help with generator
500 dynamo to 126 generator
greeting fiat 500R

Whilst I was messing about in there I took a pic of the superfluous connection tail at the battery that was fitted to the new cable and will come in very handy.
MAL_7644 by Peter Thompson, on Flickr

After all my lateral thinking and preparation, I ended up wiring the alternator by the conventional route, ie. I removed the control-box innards and used the terminal-posts to connect the alternator output to the original connection to the starter and fusebox.Although technically, this keeps some of the original look, (remembering you can't hide an alternator) I was just being practical as it means that no original cables needed snipping or removing.
MAL_1750 by Peter Thompson, on Flickr
The reason is that it turns out that the short cable to the starter connection is already about 5mm and since my headlights are now fed direct from the battery via relays, there is a much reduced current draw via the original control-box output cable. Thus it seems unlikely that any cables will be overloaded. And I connected the alternator excitor cable to the original IWL cable.
I threaded the new alternator cable along the route taken by the old dynamo cables and put it through a heat-proof sleeve to give extra protection. All terminal connections were given a coating of electrical grease.
I found the whole job was easier by removing the three pieces of the left-hand cowling, which makes fitting the impellor an easy job on the workbench The dynamo bracket used studs and the alternator uses setscrews, but I found that the studs could remain in place. The earthing strap was too short to reach once the alternator was fitted so I used a spare I had from my Citroen (Ooh...non-original!)
The "new" undertray that I bought as a reproduction,three years ago was very rusty and it is missing for the moment because I have derusted it (it looked 50 years old) painted it with epoxy primer and plan to stone-chip paint the underside before a couple of coats of Plasticote.
It was an easy if long-winded job and nice now to see the charging light go off as soon as the engine gets moving. More night rallying driving to follow

MAL_1747 by Peter Thompson, on Flickr

So you gutted the old original mechanical VR that was playing up, so if you want to revert back to the dynamo you can put the newer electronic VR back in. Is that the case?

What sort of voltage output does the alternator give out? I assume it's is pretty constant across the rev range?

I can't see your Plastikote application in those pictures? They need to be wider or are you hiding more mods?

Vitesse said:

So you gutted the old original mechanical VR that was playing up, so if you want to revert back to the dynamo you can put the newer electronic VR back in. Is that the case?

What sort of voltage output does the alternator give out? I assume it's is pretty constant across the rev range?

I can't see your Plastikote application in those pictures? They need to be wider or are you hiding more mods?

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Yes, I've read enough learned comments on the advantages of electronic regulators to know that I would never fit a mechanical regulator again. So dismantling it caused me no pain. The electronic one will just slip back in without any bother if needed, as there are no cut or removed, original wires.
The voltage steadies at around 14.2 really quickly and drops just about half a volt on tickover. When the engine is first started and all the lights are one you can actually hear the engine hurting a bit under the load.
Unfortunately, my Plastikote is of the matt variety and there is some on that front cowling but it does look a little dour. As you know, I actively avoid the freshly made look, even when I have rebuilt something, but that old alternator is functioning like new with the bearings, brushes, rectifier and voltage regulator all replaced.