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MG Midget and Sprite Technical - New wiring loom decision

While the car is in the paint shop (only took nine years!) I'm thinking I'd be better off buying a new wiring loom. Don't really want all my work going up in smoke due to some dodgy wiring.

Making that decision now opens up further decisions as there are a few options to choose from.

For example:

1. Alternator or original dynamo
2. Radio feed
3. Accessory Socket on Dash
4. Cloth or PVC
5. What if after fitting you want to add something else?

Any recommendations based on that fact my car isn't going to be winning medals for originality.

Thanks

James
James Paul

Decisions, decisions. I know the feeling. My Frog has an original new loom but I've got an alternator so I just found a wiring guide to convert. As far as accessories goes, I put in a terminal block that the main power goes to and then I just hook up any new things to it. An accessory dock is next on the list. Since you're not going concours, the sky's the limit.
Martin

James

Buy one direct from the manufacturers Autosparks. You can specify extras if you want them that deviate from OE spec.

Select your car, model, RHD or LHD, PVC or braiding and what additions/medications you want from their ‘Vehicle Finder’ and then when you click on the loom: https://www.autosparks.co.uk/finder They list ‘Sprite Mk1’ under ‘Austin Healey’.

E.g. https://www.autosparks.co.uk/austin-healey-sprite-mk1-wiring-harness-set
Or
https://www.autosparks.co.uk/austin-healey-sprite-mk1-wiring-harness-set-2

They also sell earth straps, dip switch lead etc.

Cheers
Mike
M Wood

Another vote for Autosparks however there was quite a wait for a modified loom to be made the last time I contacted them
Bob Beaumont

James
If it were me I'd go alternator and do away with the control box - simpler and more reliable plus the charging will be better (others will disagree ....). Accessories can be wired to the loom e.g. ones switched from the ignition can be derived from the heater or wipers feed - you might have to add another bullet connector under the dash.
Bill Bretherton

After 50 years with a dynamo I would not hesitate to recommend an alternator. The whole job was done, including converting to electronic tach, for less than the cost of a new dynamo. Should have done this decades ago. Don't buy the alternator kits sold by our usual suppliers and "recommended" for Spridgets, they are too expensive. You just need one for a classic Mini, usually £50 or less. You can use the standard drive belt, but positioning is better with the correct adjuster bar and shorter belt, as the pulley is smaller.

I would also suggest you think about fuses. I know your car is later than mine, but even so the standard fuses are minimal. I have separated out the main circuits and installed 8 blade fuses. Relays on heavy load items are also a good idea - headlights, radiator fan. I even have a relay on the air horns.

Regarding wiring looms, my car still has the one that I installed 40 years ago, but I have had to replace all the connectors under the bonnet because of corrosion. The rear loom has however been replaced after a short circuit episode. I made my own from a piece of trailer cable - better quality than standard.

All these modifications mean it is impossible for anyone else to know what is connected to what, so it has all been documented in diagrams and tables of connections. Frankly I have forgotten what I did so this is as much for me as anyone else!
Les Rose

James,

agreeing Bill and Les, a third vote for an alternator conversion. Much more reliable performance compared to a dynamo.
Mine's converted and also has electronic ignition, far better IMO than the standard points and condenser set up.
Jeremy MkIII

Alternator conversion? Absolutely. In the U.S., there are no longer any decent Lucas generator cores available for rebuilding. After one of the new generators made in India from Moss lasted only a year or so, I installed the alternator and have never looked back.
Glenn Mallory

Thanks everyone!
James Paul

Of course the real answer is to have two cars. Keep one as conceived for the authentic 1950's designed experience, including matched dynamo and voltage regulater. And the other to experiment on and update with all those later gizmos. Best of both worlds!
GuyW

Alternator definitely. Points ignition. I've still got the original loom, 1966. It helps of course that I've had the car since 1977, so know there is no dodgy wiring.

Guy, in comparison, have you developed a preference between your two Sprites? If you were forced to, which would you give up?
anamnesis

Anamnesis, thats like choosing between your wife or mistress, youd love them both but in a different way! LOL!!!
A de Best

LOL Yes, I love them both!
What surprises me is how different they are. Having had a 1500 before the 1275, and found them not so very different, I assumed much the same degree of separation between the 1275 and the MK1 Sprite. They are after all almost the same body tub. But the driving experience is totally different! The much increased power of a fairly highly developed 1275 was to be expected but the other differences of feel, ride, steering and cockpit controls makes such a difference. With the '50s style frog you can feel the ancestry going back to the Austin 7's that were my first cars. The 1275 feels much like a modern, or at least a basic millennial car by comparison. Little details like self cancelling stalk operated indicators and two speed self parking wipers were quite significant motoring developments in their day. Add to that all of the many modifications and upgrades I have done over the years and its a very different car.

Which to keep is a decision I haven't tackled yet. If I was doing my once much higher mileage (12k per year at one time) then it would be the modified car. But for tootling around quiet country lanes in the sunshine the Frog is just joyfu!
GuyW

😄😄 Arie.

Interesting Guy.

Having to choose between loves. Life's tough sometimes. Lol.
anamnesis

James, if it helps when I bought my new alternator I got a Lucas 18ACR (45A) from Bad Boy Classics and went back to them for the same thing for my mates GT6.
It was the best deal I found and they were a pleasure to deal with. I checked and they are still doing them, including a shiny chrome version if you like bling.
Cheers. GB.
Greybeard

Thank you!
James Paul

Hi,

I need some more help please.

I have made the decision to buy a new wiring loom and go for the alternator conversion.

Spoke to Auto Sparks and unfortunately they have a 12 to 18 week lead time due to, guess what, yes bloody covid! Well my car is coming back from the paint shop today and I don't fancy waiting that long.

Spoke to Moss who confirmed they sell the Auto Sparks looms and have some in stock for my year. Great!

However what they sell is the loom for my car which is made up for a dynamo.

Auto Sparks say that you need to have the correct wiring for the alternator as it needs a higher rated cable to handle the current.

Moss say they sell an alternator kit with everything you need. However when asked about the replacement loom / cable that comes with the kit, they said they didn't think there was any.

So what I need to know is of those that have converted from dynamo to alternator is what Auto Sparks saying correct or can you buy a kit that includes everything including the wiring.

I've attached the instructions for the Moss kit.

Many thanks

James



James Paul

If you order a new loom for a slightly later car that has the alternator wiring, what would be 'wrong' about it for your car? Could you simply conceal any wires that are not needed?
Jonathan Severn

James

I agree with Jonathan - an alternator loom has the cables built in for the alternator and will also leave out connections to the control unit/ regulator (which you'd otherwise have to deal with). Any un-needed wires can just be terminated. I'm assuming the high beam and charging indicator bulbs will be the same way round.
Bill Bretherton

While I'm sure Autosparks are correct in theory, in practice many cars (including mine) have been converted from dynamo to alternator using existing wiring without issues.

Yes an alternator can provide more current than a dynamo but unless you have a duff battery or something to draw that current (thinks several massive halogen rally lights?) it won't actually do it for long enough to overheat anything.

AdrianR

Completely agree Adrian.

Unless new looms (for cheapness), are made with lower current carrying capacity than the originals were, then a dynamo loom will be perfectly capable of coping with an alternator. It's not so much what the generator (alternator or dynamo) puts out, but rather, what you draw as Adrian said.

Mu '66 Sprite still has it's original dynamo loom. I converted it to an alternator over 40 years ago. No problems at all.

So rather than wait, just get a dynamo loom.

anamnesis

Ordering a loom for a later car will have its own problems.

Alternators weren’t fitted until 1973 (UK), by which time 4-way fuse boxes were fitted, different instruments with voltage stabiliser, wiper motor wiring, different column switch with a multi-plug, etc.
Dave O'Neill 2

Surely the only increased current will be between the alternator and battery - or wherever it feeds to. Why would anything else change? On mine this was to the starter solenoid post which then feeds to the battery with the heavy starter capacity cable. I don't think I upgraded any of the wires on my existing 1971 loom.
GuyW

Yeah, if you are worried you could add a second cable in parallel to the loom (Lucas alternators have two terminals available), but there's really no need.
AdrianR

Anam, Guy

what did you do about the regulator connections which are no longer needed? Did you keep the reg and re-wire it?
Bill Bretherton

Mine was done in the late 80's with a s/hand alternator from a rusted Maxi. I removed the regulator and after consulting the Haynes manual wiring diagram applied a couple of scotchlocks to bridge the connections - things were simpler then :)
AdrianR

As Adrian, my alternator was ex- scrapyard, though I cannot remember off what. I got advice, probably from here, and removed the regulator and connected a couple of wires together instead. I have probably got a diagram or note somewhere of which wires to connect together.
GuyW

Alternatively you can retain the old regulator as an anchor for the cable ends after disconnecting its workings from its terminals, and bridging between terminals as required.

The connections are simple:
Join the brown yellow to the brown green to complete the exciter circuit.
Join all the heavy cables together.

Can be done by soldering unseen links inside the regulator base, or with external links between terminals.
Paul Walbran

On balance, it does seem best to get an earlier dynamo wiring loom and re-wire the regulator connections as that sounds simpler than modifying the later connectors behind the dash.

However, if there are high wattage headlights and other upgrades it may be worth adding an additional alternator to battery charging cable.
Bill Bretherton

Thanks for all your advice.

New loom ordered and delivered next week!

Will go for alternator conversion when I'm closer to getting the engine in.

Got one or two jobs to do before that!

Many thanks

James
James Paul

Nothing to do with wiring, you have enough on that already. Just to say the car is looking great! What is the inside painted with?
Malcolm

Hi Malcolm,

Thanks yes it has been a long journey so far and good to get to this stage.

I’ve painted it with chassis black. Didn’t see the point in spending the money on spraying it with the colour when it is going to be covered up.

We’re going to paint stone chip in the wings and wheel arches when I’m ready to fit the wings
James Paul

Top job. It makes me want to pull mine apart and sort the paintwork out once and for all. My rattle can job is looking a bit dowdy now! Its about eight years since I did it, a few years of which the car lived outside and it's red as well so prone to fading. :-(
Malcolm

Did you spray the whole car Malcolm?
How many, what size cans did that take? I used a small electric spray gun, used about 2.5 litres m99 hmg celly gloss.
anamnesis

I can't remember Anam. Too many years (and beers) have gone by since I did it!

At the time I didn't have ready access to power (and I wanted to do it myself) so spray cans were about the only option. It, on the whole, worked well but as time has passed it hasn't been particularly durable.

I think it needs flatting back and clear coating to bring back the shine and depth of colour.

Malc.
Malcolm

Well if it's lasted well enough, that you can contemplate cutting it back to restore colour and shine, it can't have been that bad a job.
anamnesis

This thread was discussed between 26/04/2022 and 20/05/2022

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