From: Steve Jones - PWA7 - [email protected]
Date: 21 Feb 2001
Time: 00:00:19
Remote Name: 205.188.193.52
Alan: Sounds like the half charge resistor in the dynamo has burnt out - a very common problem. I am a bigger electro-phobe than you but I know a man who isn't and this is what to do.
Obtain a modern 25 Watt resistor, preferably with a finned al. case to aid heat disipation. Maplins sell what you want in the U.K. under part no.T+25 or P+25. For you, Maplins The Broughton Centre, Chester or London Rd. Stoke seems nearest. Cost is £1-99 inc. VAT. Check that it is the half charge resistor that has failed by connecting your new unit between the two terminals on the top of your dynamo. Leave the existing wiring connected also. Run the engine and if you now get a charge on the ammeter of around 2-4 amps at reasonable revs you have confirmed the diagnosis. Remove the new resistor and now connect it between F1 and +D on the back of your ignition switch - effectivly connecting it to the dynamo terminals as previous. If connecting this to a Chummy type switch panel, connect between SH and +D. It does not matter at any stage which way round you connect the resistor. The Maplins type comes with a handy pair of fixing lugs and you can use these to fasten your resistor to one of the patent plate bolts to keep things tidy. You should now have a working Summer/Winter charge. If the resistor comes without leads, you will need to solder one to each of its terminals, say about3" long. This modification was given to me by Alan Billington of Pre-War who understands these things and has been fitted to many cars (my Box, Chummy and Trials Car included) and works without any further attention. You will notice a small amount of heat build up around the fixing but this is only the resistor doing what it is supposed to do.