colours of wires with alternator

[foy9999]

Just a quick question after looking at the wiring-diagram in the Tim Millington book, also shown in Sticky posted by John A Ross

It looks like N & NB coming from the alternator which would be Brown & Brown/Black. The latter seems an unusual combo. The letters are hard to see on the diagram so it might actually be NR (Brown/Red), not NB

I know with the dynamo-equipped cars it was N/Y (Brown/Yellow) & N/G (Brown/Green)

fwiw my (1965) loom was previously altered to take an alternator and the wires colours are hopefully clear in the pic below. I'm a bit colour-blind so not sure what they are. (I get red/brown and green/brown mixed-up worst)


lead to alternator


Actually, after posting, and zooming-in on my pic am thinking the thinner wire is actually Brown/Black

[John A. Ross]

Graham

What year is you car ? and I am assuming its a Lucas style alternator and not a denso or bosch ?

Thicker borwn wire is the alternator output and should be rated as per the alrternator capability, if you expect it to charge at max (usually 45-55A) then that cable should be rated at that and a bit more if needed use the two wire spades. For an alternator setup this should connect direct to the battery post on the solenoid. Dont use the cars loom, the wiring is rated a lot less than the alternator can supply.

The thinner one is the ignition lamp.

From the ignition lamp at dash to the RB340 the colour is NY (Brown/Yellow) and that should pop out the loom at the RB340 somewhere and if the RB340 is still connected onto the W/L terminal.

Now the D terminal is actually connected to W/L internally on the RB340

The D terminal on the RB340 is also NY (Brown/Yellow) and did connect to the old dynamo,

2 Choices,

Disconnect the wire from the W/L terminal on the RB340, extend to alternator plug.
Disconnect wires ffrom W/L and D on RB340 and connect together(but disconnected from the Rb340) and use existing wire to alternator plug.


Actual brown wire for alternator output is Brown/Green but beware, the wire from the dynamo is only good for 30A or so when warm, add a few spots and say a heated rear screen and you can pull 40A over it and thats too much.

The alternative would be to fuse the existing Broen/Green wire from alternator to car at 25A with an inline fuse to avoid any risk of overload on the wire.

John

[foy9999]

Thanks for the comprehensive reply John A. Ross

It's a 1965 car and was fitted with a Lucas ACR16 alternator in, I'm guessing, the early 80s.

I have both options (Dynamo & Alternator) and at this stage am just trying to work out what's easiest option to use. Plus I find it interesting to find out about these things


16ACR not fitted to Imps till post-1969, per parts-list

[John A. Ross]

Graham

The decision to restore to dynamo or use alternator would be up to you, the car can accept both with exception of the simple wiring change and the alternator bracket

Your 1965 would have been a dynamo car.

The dynamo setup is more complicated, you need to have the dynamo in good order, they are about £120 exchange refurbished and last just as long as alternators, the failure myth is just that, life span taken from date of ownership to failure rather than actual life span. The date code is on the side and most date from 65-72 so a failure 30 years later is a good innings
and no expectaions of not getting that lifespan again out of a refurbished one if done well.

The RB340 seems to be a bit of voodum to many, it needs to be in good order (especially the resistors and connection on back) as the box is realistically just voltage controlled relays. Adjustment is not hard and the Lucas manuals can be downloaded here. Refurbished ones huit about £60, new cheaper ones are available. If you swap the top covers you can even make it look old

So we are at nearly £200 now and worth spending if original is your thing.

Alternators you can buy new for £40-£60, buy from local motor factors or trusted source as the cheap ones on sale online, many are very poorly made, inbalance on fans/pulleys, crap recifier slab, poor internal connections some not even tighten the nuts.

Then you need an alternator bracket (assume rootes block not B1) to fully support the alternator. The alternator is heavy and if you are in the habit of giving it some, worn mounts or just an engine that the timing or carb is off and lumpy, the outer casing will eventually fracture.

Never fit an old ACR, the alloy may be weak and your back to failure if it craps out. For £40-60 quid its not worth doing the job twice

Wiring wise they are more or less the same and the car can be left mostly intact.

With one exception and I have seen it happen.

The alternator will deliver on demand, so if you have a 45-55A alternator it will deliver that through the under-rated imp wiring if the load demand OR IF THE IMP WIRING SHORTS so you get loom meltdown and engine bay meltdown. Always fuse the alternator and fuse the feed from battery to car accordingly

Just needs a decision on which way to go and execute

On all our MK 1s we have continued to use dynamos and RB340s and have had one failure on the dynamo which was the front bearing and I do not think it was the dynamo, more like the rattling water pump pully vibration just accelerated failure

[foy9999]

Thanks again for comprehensive reply John A. Ross

I have the correct rear bracket for an alternator and several front ones but it's not really clear which front one is correct as there are several types and no part number on them. I think it's something to do with the stud position.

Anyway I think I'll go down the dynamo route as that's what my car would have had at start - altho the parts list dos show pre-1969 alternator option (10AC and 11AC)


Imp rear support-bracket for alternator


lots of different adjusting arms (painted one is probably for alternator)