Dynamo Terminals and interchangeability

[James Anderson]

I appreciate these may be simple questions but electrics are not at all my forte and from what I've studied following various searches, this ignorance is further emphasised! Firstly on a late C35A Dynamo, is the big terminal the D (Dynamo) and the smaller one the F (Field) pole? Secondly, are these types of dynamo i.e. 'M' for 'A' and vice versa, directly interchangeable?

[David Stepney]

On both types of dynamo, when looking from the distributor end, the 'D' terminal is the left one and the 'F' terminal is on the right.

Although both types of dynamo are mechanically interchangeable, they are not electrically. The C35A has the half charge field resistor built into the top of the instrument under a cover on top of the dynamo which also houses the field fuse. The CF1 cutout for this type of dynamo is just a cutout and does not have a field resistor in it. If you fit a later type C35M dynamo, you will have no 'half charge' unless you interpose a 2 ohm resistor between the 'F' terminal and earth. The charging/lighting switch shorts this resistor out on the 'full charge' position.

The later CF3 type of cutout for use with the C35M dynamo has a field resistor and fuse built into it.

Hope this helps.

[James Anderson]

Thanks David, I think my ignorance is worse than I first thought, I had a closer look at my only spare rebuilt dynamo and the only writing I can make out is DEL29, so it looks as if this was off one of the earlier A7s, probably the first coil engine versions. So it looks as if my problem is worse! It does seem odd that there are so many variations on a theme but sadly it looks as if I'll be chargeless for a while! I'd be grateful if anyone has a rebuilt C35M they want to sell and/or who is best to contact to rebuild my existing one as soon as possible.

[David Stepney]

Try this chap:- Trevor Fawcett. email: trevazit@hotmail.com.

i came across him on ebay when I bought a refurbished distributor from him. I was so impressed that I got him to refurbish my old one. I know he does dynamos and starters so it may be worth your while to contact him. His charges , at least for the distributor rebuild, were quite reasonable.

[James Anderson]

Thanks David, I'll contact him tomorrow.

[Bob Culver]

I am not sure if all 35A had the box attached and many have been adapted without.
The previous DEL 4 field pole dynamo originally had an internal field resistor which is usually now defunct. Now usually arranged as later (very confusing to those unfamiliar.) Fully useable although safe max output reckoned to be somewhat less than 35M. 8 amps no load charge on ammeter reckoned OK.The internal armature connections differ from common Lucas and can confound the unfamiliar.
The electrics are very simple but complicated by the lack of original circuit diags. With Cornforth diag much more clear. The Cornwall site has an article covering the various charging cct arrangements, helpful to any auto electrician unfamiliar. many combinations are encountered.

[James Anderson]

David, I sent an email to that address but unfortunately it came back as 'unknown'. wonder how long ago you had work done and/or whether he's given up doing such work or there's some other explanation.

[David Stepney]

Sorry James. I hvae rechecked the email and find that it is:- trefazit@hotmail.com.

I must have mistranscribed it into my address book!

[James Anderson]

Thanks! I'll try that one....I'm always doing things like that.

[Dave Mann]

    In this photo the D terminal is on the left and F on the right. It also shows how i drive the dynamo with an electric drill.