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Wiring Lightweight Nippon-Denso Alternator Triumph

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This is how to WIRE Nippon-Denso alternators; like this shown below.


Fitting to: Spitfires and GT6 Triumphs. Maybe applicable to ANY Triumph with some commonsense poured on, even MG and any LUCAS equipped classic.







This is NOT a procedure for retro fitting Triumph Lucas alternators.


This covers the Nippon-Denso, Kubota, Brise Alternators.


I LOVE these alternators. 40AMP BULLITPROOF total Japanese reliability.


If the Alternator looked those shown above, it should be good to go, BAR if it's a 1 wire model (covered at the very end of this article).


I will cover fitting them later, from the info here, you should be able to rewire an ALTERNATOR equipped 1500 or GT6 Mk3 or any British car with some thought.


This is the procedure for wiring it to a dynamo equipped Triumph Spitfire Mk1-2-3 or GT6 Mk1-2


First technique is using existing wiring, advise taking the time to REWIRE and not following this section.


You will need to remove the control box for GOOD.


At the control box you will see as shown below 6 terminals




1, connected = 2x BROWN (1 to ignition switch, 1 to Starter Solenoid

2, connected = 1x BROWN (to LIGHT SWITCH)

3, connected = 1x Thin Brown/Green (to small connection on Dynamo)

4, connected = 1x Thin Brown Yellow (to ignition warning lamp on Speedo)

5, connected = LARGE Brown/Yellow (main power feed from Dynamo)

6, connected = Black (Earth to body)


Firstly remove the black wire (6) and remove it from the car completely. It's no longer needed.


Remove all the wires, label them as above, 1-2-3 etc and remove the control box, save it!


Maybe give it to a friend?


We now have a bunch of wires.


Strip off the connectors and insulations from ALL of them.


Get the Large Brown/Yellow wire (was connected to 5) and the 3x Large Brown wires (were connected to 1-2). These must be joined together; solder and heat shrink them to link them all together.


This now means the Alternator is driving the power into these brown wires, as needed and they are connected and the battery is charged from brown wire going to the solenoid.




That's stage 1 of the not rewiring technique, done.




The Denso alternator needs a different method from some others from here on.

On the Alternator (if 3 wire) you will see a small connector box with two spade terminals and a stud.  The main powering wire/charging wire, the Thick Brown/Yellow must be connected to this via a ring terminal.




Above shows a Thick White Wire, think of this as the Thick Brown/Yellow Main charging feed.


You need to add two other cables now, some really thin 11amp will be MORE than adequate.


Ref 11. 16/0.20mm, 0.5mm2, 11amp.



The thin green in the image above MUST go to the ignition switch, to a switched feed, so only powered with the IGN on. So find some cable and join the (IG) terminal on the Alternator to a SWITCHED ignition source (green wire in my picture), this must ONLY be powered when the ignition is on. This energises the alternator, turns it on ready for use.


The black wire shown above is an EARTH SWITCH.


To get the charging light working properly. Follow these steps.


Gain access to the back of the speedo, find the ignition warning light unit/holder which push fits into the speedo. You will need to discard this as the modern alternator system doesn't work in the same way. On the IGN warning light holder you will see a white wire (which goes to the ignition switch (+) and a thin brown/yellow (which did go to (4) on the control box).


Snip the connections from the rear of the IGN warning lamp holder, discard the lamp holder. If you wish remove the entire length of the brown/yellow wire going to the control box, leave the loom open and rewrap it later, after going through all steps in this article, especially if going for the total rewire method). Or just leave it there; cover the end with shrink wrap.


To get the IGN warning light working.


Buy one these lamp units.




Images below show the unit will fit in the old lamp holder boss on the instrument.





Just CAREFULLY chop the end off (by my finger) and insert it the opposite way around to my demonstration. Chamfer the end and thin down the plastic a little.


Connect the white wiring you chopped off the old unit onto one side of this new lamp (its got two spades on) and from the other side run a NEW black wire to the alternator spade marked L (as seen above in images of the connections on my alternator, with the black wire connected to it). This will now switch OFF the earth connection when the alternator starts making voltage, so putting this light OUT when the alternator is working.


You now have a working alternator with a working IGN lamp.




If you wish to REWIRE the system, follow the instructions below.



2, Total Rewire of Mk1-2-3 Spitfire and GT6 Mk1-2.

Read above and get a handle on what goes where.


Repeat the procedure for wiring the two small connectors from the alternator, including the IGN warning light mod.


You now have 4 wires to deal with. The main brown/yellow wire that goes to the Alternator (main charging feed).


You have 3 browns.


I suggest buying 5metres of new brown wire (33AMP) and 2metres of new Brown/Yellow (39AMP), cause I hate spliced up spaghetti, its bad for resistance.




Ref 33 . 44/0.30mm, 3mm2, 33amp brown 5metres

Ref 39. 56/0.30mm, 4mm2, 39amp brown/yellow 2metres


You will also need 4x 8mm ring connectors


RD8 x4


You will need 2x normal female spade connectors and two rubber boots.


FB66 x2 (you can only buy 10 min)

FBI66 x2 (10min quanity)


Now we are ready to do some wiring.




As I said I hate joined up cables, you can do that if you want, I mean splice in extra lengths inplace of this rewire? If so read on. You can do this a number of ways....Read this article and do what you like.




The brown wire that was on (1) on the control box can be discarded completely (it went to the solenoid)


You are now left with two browns,one was on (1) and one that was on (2).


(1)     Goes to the ignition switch.

(2)     Goes to the light switch.


You want to strip out these wires completely from the control box to the light and ignition switch, chuck them. I never liked the way these super high powered wires had NO fuse on them.

You can now add a small fuse box where the control box was or anywhere between the solenoid where these wires will terminate and the switches, so fusing these connections, I�ll leave that to you.


Use the new brown wire and run it through the car, 1 wire to the ignition switch and one to the light switch where the old wires were on the correct terminals.


(1 TERMINAL on IGN) and (4 TERMINAL on the light switch)


Solder on the spade connections to the switch ends, not forgetting to fit the rubber boot FIRST. Fit these two wires to the switches (IGN/LIGHT) run them neatly back along the wiring loom and out of the bulkhead into the engine bay.


You want these wires to terminate/join onto the starter solenoid the same side as the main battery wire using two of the Ring Connectors. Neaten it all up and route it well, then fix these wires on the solenoid.


So you have removed 1 of the 3 control box browns completely and re-routed the other two.


You now have just 1 wire left the original dynamo wire. Discard this.


Get your new length of brown / yellow and solder on a ring connector to the one end, fix this to the alternator, (as the white wire on the image of my setup). I suggest attaching this wire directly to the battery (+) terminal.


You can manage that, if the main terminal on the battery is REALLY OLD it will be a lead job moulded onto a cable or it maybe some other type. Basically just affix the cable to the terminal.


This charging wire can go on the solenoid where the other two brown wires are, its just my preference to run it to the battery


That's it your done, attach the battery.


I suggest just tapping the terminal on the battery lug a few times, quickly and just check you have done nothing wrong. If it sparks you may wish to seek professional advise!




I offer no warrenty on this information.




I do advise breaking the two brown wires that enter the cabin and go the IGN switch and Light Switch with a fuse box and run 40AMP fuses in there, you can hide the fuse box in the bulkhead etc.


To me the lack of fuses here is DANGEROUS. If you have a light switch failure or are fiddling with something and one of those browns gets an earth your ENTIRE LOOM IS SMOKED IN UNDER 10seconds.


I know cause???


If you have a 1 wire only alternator, simply connect it straight to battery. Do all of the rewiring section, but do not add an IGN feed to the alternator, or mess with the IGN warning light, cause neither will work or be needed, it's a 1 wire! Your ignition warning light will be unworkable. So disconnect its power and let it rest.


So, Just take the two browns I talked about above that retained, that were going to the IGN and Light switch and affix them to the solenoid as covered above. Removing the original Brown wire than was going to the solenoid, completely, as above. Your good to go, just ignore the sections covering the two other wires from the alternator.




Chances are the Denso alternator will do 200,000miles before it wears out, ALOT more than you will!






I am sure you can work it out its all there.



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  • 1 month later...

Hi Dave

Sorry to ask but i may be being stupid or not ?

I have followed the instructions to the letter even though i have a three pin denso alternator, have worked out the third pin is voltage sensor (it goes to the solnoid to manage out put voltage)

And the unit is now charging and car runs.


My problem is the charging light,

You state (as i understand it) one wire from the light to the altnernator  (position L) on the correct terminal, the other to the original white wire from the ignition switch, ?

Now what i have got is the light on all the time, it starts off dim before starting and brightens when engine runing ?


Not sure how i have got this wrong,


Alternator is running and producing 14.2 volts so all that looks good any ideas?

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  • 1 month later...

Just for reference i have installed my Denso this afternoon.


On my spitfire (im guessing all later Triumphs that have no control box and just an Alternator will be the same) all i had to do was run one wire to the alternator. The main battery power and IGN warning light worked by simply changing the crimp connections and plugging in.


The original IGN circuit puts 12v to the bulb and uses the original alternator as an earth. On the original system the alternator would put out a 12V feed to the bulb and cancel it out once energised.


With the Denso it just opens the circuit and breaks the earth, extinguishing the bulb, so works perfectly fine.


Put the small brown/yellow wire to the warning lamp spade pin on the Denso.


Put a ring terminal on the big fat brown wire and connect to the M6 stud on the alternator.


Just run an ignition feed to the other spade connector and jobs a gudden!




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I got exactly the same result on a TR4 last week. Just needed the extra wire from ignition and all worked fine. Unfortunately the mounting boss on the ND alternator puts it way off alignment for the V8 else I'd have had one on that too. Not to worry - got a high output one in standard LRA100 casing coming from MGOC of all places.  Not being funny but Triumph clubs could do a lot worse than take a look at what MGOC offers its members.  I had to join you understand,  I look after a lot of MGs so it was a business decision.

Wooly jumper comes later, beard once a  week!



Willow Triumph

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I got exactly the same result on a TR4 last week. Just needed the extra wire from ignition and all worked fine. Unfortunately the mounting boss on the ND alternator puts it way off alignment for the V8 else I'd have had one on that too. Not to worry - got a high output one in standard LRA100 casing coming from MGOC of all places.  Not being funny but Triumph clubs could do a lot worse than take a look at what MGOC offers its members.  I had to join you understand,  I look after a lot of MGs so it was a business decision.

Wooly jumper comes later, beard once a  week!



Willow Triumph


Allo Tim,


Good to see you on the forum!


I will check out the MGOC, don the false beard! I think this place is giving a lot of people the upgrade bug!






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One question:  Does the mounting hole on the alternator match the engine mount? or are shims, or some other fab needed?




Matches but you need to space it out to get it lined up with the pulleys ok on the bottom mount. I used washers for testing purposes (bodge!) but im getting a spacer made up as we speak.


Top mount just fabricate a bracket.


Fan belt i used is 10mm Width and 1150mm in Length.



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I found by mounting the alternator 'upside down', the pulley lined up perfectly.  The only modification I had to do was drill out the thread.





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  • 1 month later...

well after the dolly one failed on me i managed to pick one up localy for £20 so made my mind up on wether to get another lucas one or not! on the sprint its abit harder to fit but in the end i just decided to use 2 alternator mounts and it sits fine now, and wireing was simple enough, just used to the old stuff and joined the 2 brown wires together and soldered t the ring terminal, then the yellow and brown one to the spade that was furthest away from the ring term, and then made up a wire that went to the one in the middle to and ign live. and works fine, easy peasy!

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  • 3 months later...
  • 3 weeks later...

I bought the Denso unit with multi-V belt pulley.

Got the pulley of, strangely it doesn't have a woordruff key?

Then tried a Lucas pulley on.

Hole matches so no spacer needed, only it is to thick, the nut only just engages the first few threads.

But this is easy to fix.



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