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Dynamo to alternator : modifying an old control box


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Hello guys,

 

Sorry to ask, I have lost the info in my computer : how to modify an old control box to allow the fitment of an alternator on a TR3A, without alteration to the main harness ?

 

This modification consist in a few "bridge" connections and some others modifications in the old (and then unused) dynamo' control box, as the alternator don't need it anymore.

 

Who can help ?

 

Chris.

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I don't think it's necessary to do anything other than connect the output from the alternator straight to the positive of the battery. Alternators produce a lot more current than dynamos, so best not test old wiring with it.

 

Obviously the car will be positive earth and the Ammeter will show a permanent dish charge if it's reversed, but it'll all work fine. Ash

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Ash, I will keep the old control box + wiring to allow the "retrofit" of a dynamo later, if needed, but it will be a "fake" control box, with all the innards removed.

 

This particular car has a brand new wiring loom, and I don't want to cut any wire, thus the need to connect the wire via the old control box.

 

I have bring theses mods to some cars, but have lost the scheme of mods to bring to the control box :(

 

BTW, a car with alternator must be negative earth.

 

 

Chris.

Edited by Chris59
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Hi Chris59, I've carried out the conversion to an alternator on my TR3A and still use the (modified) control box as I want the car to look 'original'. If you could let me have your email address I can send you some photo's showing the modified wiring. I've been unable to attach the photo's to this reply as they are too large.

 

Tom. :rolleyes:

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If the alternator is of modest output, such as the 34 amp rated unit which I have fitted (as on early TR7s), then the existing wiring, provided it is in good condition, should be adequate.

However, if a device capable of driving a cooker, refrigerator and washing machine has been fitted, then suitable precautions need to be taken (see TR Action 248)!

Ian Cornish

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Connecting the alternator main charging wire direct to the battery is an excellent idea but you will get odd information and needle swings from your ammeter. The ammeter will tend to shew a continuous charge as the amps flow from the charging input of the alternator at the battery into the car circuit where the demand is.

 

On TR2-3-3A-3B - I have not looked at the standard circuit for TR4-4A

 

Cheers

Peter W

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Hello guys,

Thanks for all the inputs.

On this perticular car, I'll more than double the "charging" cable : the alternator is a 45amp, and the orignal cable isn't big enough to cope with the power.

About the ammeter, I don't think it is really usefull on a car with an alternator : a volmeter is more adequate, IMHO.

Cheers,

Chris.

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If you connect the alternator directly to the battery, the ammeter will never show a charge, it'll just show the current being drawn by ignition, lights etc.

 

If you wire a 45 Amp alternator through the ammeter, it'll go up in smoke!

 

And if you leave the wiring standard, the dynamo can go back on if originality becomes important.

 

Ash

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  • 9 years later...

Ok so I've fitted the thin belt alternator conversion to my 4a restoration project (+ new loom) and am looking for a bit more detail on the modification to the old control box. I assume you can remove the internals and replace with a suitable heavy duty connection to link the correct wires? I've seen a couple of posts with the 'Dynator' fitment but not sure if the alternator arrangement is a bit different; this is not about the wiring set up but more about the modification to the old control box internals

Many thanks 

David

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Remove internals.  Using reasonably heavy wire the only connections should be:

D to A & A1       F to E

Disconnect earth wire from E, & discard

Connect ign warning light wire (thin yellow) to E

Connect field wire from alternator to F

Connect power wire from alternator to D

Leave wires on A & A1 as before.

Bob.

Edited by Lebro
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This is my annotated regulator for the alt conversion for an on car reminder. Tom’s wiring pic is the right one that I added my annotation when he helped me.

89E68A17-4577-43FA-91AD-7951475841AA.jpeg

BA032B65-3BA5-483A-A4F8-1A1FCFC2BEBD.jpeg

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