Conversion from dynamo to alternator

[Vonkie]

As my Day drew nearer, and I test drove her on Sunday, some charging and timing snags needed sorting out prior to the retrim, which should happen next week. And so my seller discovered that my 1963 series 1 3.8 had actually had a conversion done replacing the dynamo generator with an alternator - apparently well disguised with the old shell left in situ and the dynamo regulator cover also left in situ. This was quite a surprise. I thought we had established, at an early stage, with reference to the number imprinted on the regulator box, that the dynamo was the C42 30 amp version, rather than the C45 25 amp version (this to be expected, given that this change had already occurred in August 1961, according to Clausager p33). But this was all an illusion, based on the false assumption that the covers contained a dynamo and regulator rather than an alternator-regulator combo. I should presumably try to ascertain the specifications for the alternator.

I assume that I should stick with this (at least for now) and not now try to revert to the original dynamo system. Although the alternator is an unoriginal conversion on the 3.8, and does away with a rather quaint quirk, I suppose it falls somewhere in the same-ish category (tolerated and maybe even desired) as Kenlowe fan (also done) and extra callipers (also done), and not in the same category as 5-speed conversion (which had been done, but which I asked be undone to have the car's original Moss box restored and refitted). I understand that, generally, converting to the alternator tends to reduce charging issues (after all, this was one of the improvements in the 4.2). Anyway. Maybe I'm persuading myself. What's done is done, and I could always take a retrograde step at some later stage if I feel so inclined.

(By the way, insisting on restoring the Moss Box was one of the best things I did. It shifts really nicely, and my fears and nerves in this regard appear to have been misplaced. After a few driver errors, like going to reverse instead of first, struggling to find second, and going to first instead of third, I got used to the counter-intuitively small shifting area and felt I would quickly master this completely, without too much requisite double de-clutching skill.)

Anyway, back to the alternator conversion. What I should love to have some tips on from the boffins on this forum are the kinds of things I need to know that result from, or ought to be adjusted because of, such a conversion. I was, for example, wondering whether the polarity ought to have been changed to negative earth (if it even was positive to start with), whether the timing would be affected, and whether the manual choke operation ought still to be operated as it would have been with the dynamo (the 4.2 that came out with the alternator also came out with an automatic choke, methinks). Which instructions in the books aimed at the original 3.8 with its dynamo charging system must now be adjusted for the alternator system?

No doubt certain things one would do in the dynamo world, one would not do in the alternator world, and vice versa. Any help in this regard would be very much appreciated. I want to learn everything I can about my car, and things get complicated when the charging system is more akin to that of the 4.2, and one needs to know what adjustments this gives rise to, and what to look out for.

[lopena]

Frank:

Since your car now runs an alternator it is definitely negative-ground. That being said, there really are no differences (vs. positive-ground) in how the car operates, including the timing and the functioning of the choke.

Don't over-think this...the substitution of an alternator for a generator has virtually no impact on the driving experience (except maybe on a cold, rainy night when you're running the headlights, wipers and defroster).

And I applaud your decision to stick with the Moss box...it's one of the traits that defines a very early E-type.

Good luck,
Alan
NJ

[Heuer]

Sounds like you have a Dynator fitted: https://www.autoelectricsupplies.co.uk/product_list/197

A good conversion that simplifies the charging system by eliminating the need for the control box which can be kept in situ to give the original look. Leave it as it is as it no way compromises the operation of the car. It would be worth understanding if the car has also been switched to -ve earth (usually the case); check which battery terminal lead goes to the earth point. Nothing to adjust and no difference in operation other than the alternator will charge at idle once the throttle has been blipped, which is an advantage. The 4.2 cars did not have an automatic choke so just treat the car as though it still had a generator. Both a generator and alternator do the same job, that of generating electricity to charge the battery - they just do it in a different way.

Slightly more important is to understand if the car is +ve or -ve earth especially if you want to plug your phone or SatNav into the cigar lighter socket. Also check the coil terminals which will be marked either CB (contact breaker) and SW (switch) or +ve and -ve and tell us what colour wire goes to each - there will be a white and white/black wires - and let us know what you find.

[Vonkie]

Thanks Alan and Heuer.

I've asked the seller to verify and ascertain the polarity (I'm also having one of those Long Beach radios with faux 1960s faces done, so I'm sure it won't work properly unless everything's gone to negative earth?), and I'll ask him to verify that the alternator set was a Dynator, so I know for future troubleshooting and wiring issues.

I don't have the car with me so cannot myself check the wires, but will ask him specifically to look at coil terminals and battery terminals.

Many thanks!

[cactusman]

Highly likely to be negative earth....just see which battery terminal is connected to the body. If it has been done well and works then I'd stick. Only thing to be aware of is that 3.8 cars had a (pretty useless) amp meter showing charge/discharge. It is rated at +/- 30 amps and the alternator you have will be able to produce 40 amps or more if the battery is really flat. Just make sure the wiring and especially the various connectors are in good order and really tight. Assuming the conversion did not affect the loom then if you did decide to revert to a dynamo then it would be very simple. Just replace the empty regulator box with an operational RB340 one. Reproduction units are available and there is also an electronic version available from someone in the US. Original ones show upon eBay regularly but may not work well or at all