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Charging,?.
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29-05-2020, 02:37 PM
The quick way of checking whether it is a problem with the charging switch is to run a wire directly from the dynamo field terminal to the 'D' terminal on the cutout, linking the dynamo D and F terminals together. If the cutout then works and the dynamo charges, then it is definitely the switch.
A bit of success, but more questions than answers
The dynamo turns out to be a type C35M 220298 (So Late Ruby ?) Rebuilt post war as the pole screws are Phillips drive, not slotted! , the cut out is a CF (no suffix number). The cut out is not operating ...Checking the cut out with a decent meter the readings were 370k (tiny) not 60 ohms...conclusion voltage coil is dead! I don't think the CF is particularly compatible with the C35M (which may or may not have a functioning resistance and would usually have been mated with a CFR/ CFR2. What to do? Have the CF rewound (by who?) and put a resistance wire between the dynamo terminals. Find a CFR /CFR2? Does the lingering doubt about the switchboard (probably no functioning resistance from Winter to Summer) matter? Just drive on the battery (Good short term solution!) and see how the engine feels after a bit of use!! Thanks for continuing advice...one thing I have learnt...find out what EXACTLY you have got and take accurate readings I think my brain hurts! I am at one with John P and his starter!
30-05-2020, 06:54 PM
David.
You should have no difficulty in running a C35M dynamo with a CF1 cutout. MY RP saloon has exactly this arrangement. My switch is (of course) not the same pattern as yours, but it should work in the same way:- On winter charge, it connects the dynamo D and F wires together. On Summer charge, it disconnects them and allows the field current to run to the D terminal via an approximately 2 ohm resistor which is wired permanently between the two terminals. On the C35A instrument, this resistor lived with the field fuse under a cover on top of the dynamo itself. What I have done is to interpose a power resistor between the D and F terminals on the back of the switch and hide the resistor itself under the dash. I hope this helps, but it is beginning to to sound as if you have two problems:- a dodgy cutout and a problem with the switch. 
31-05-2020, 07:32 AM
(This post was last modified: 31-05-2020, 07:42 AM by andrew34ruby.)
As an alternative to the (faulty) cutout you can use a diode, or several diodes. Suitable diodes are readily available out of an old lucas alternator. Alternators from around 1975 to beyond 2000 are suitable. Either take from an old alternator or buy the diode pack as a spare part. I took three diodes out of the pack and connected them in parallel with each other, in series with the D terminal of the dynamo and connected with the battery. It works.
I'm running at 12 volts, but this should be equally suitable for 6 volts. Here is the sort of rectifier I used, cut up to provide the diodes. https://www.ebay.co.uk/itm/LUCAS-15ACR-1...SwgN5eMdwF
10-06-2020, 08:02 PM
At last a clear result!
Today it was established that it is just TheCF cut out that is faulty! Solid 30 volts out of the dynamo and about 10 to 12 amps on the ammeter on winter setting. So who can rebuild a CF, or supply an alternative CFR /CFR2? Thanks to all who have borne with me! David 
10-06-2020, 10:00 PM
David, My first port of call would be a word with Tony Betts and see if he had a viable replacement cut-out?
Phone/Fax 0116 2867522 Mobile 0781 6612527 
11-06-2020, 07:58 AM
David. Excellent news. I would adjust the 3rd brush to turn down the output on winter setting to no more than 8 amps, too much can damage the dynamo.
08-07-2020, 06:11 PM
Tony Betts supplied cut out did the trick. A slightly later one with resistor built in. I re routed the lead from the switch panel to F2 on the "new" cut out and then on to the Field terminal on the dynamo. Summer and Winter charges ...perfect. I tried it with jury rigged wires first and then did it properly. Fortunately I had enough slack in the cable to be able to re route without resorting to splicing in a new piece.
Thanks to all on the forum who offered advice and help David |
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