PeterC Posted February 27, 2020 Share Posted February 27, 2020 The Bosch 24 volt coil on my Hotchkiss M201 has broken. Can I fit a 24v coil from a Land Rover FFR (Land Rover Ignition Coil 24 Volt FFR 552765 LU/45120 2920-99-806-6451)? A picture of the broken coil, is attached (it is not standard to the M201). Quote Link to comment Share on other sites More sharing options...
fv1609 Posted February 27, 2020 Share Posted February 27, 2020 Peter is your Bosch coil actually rated at 24v or is it rated to operate in the 24v system of your M201 ie it operates in series with a ballast resistor? The Land Rover "24v" coil is actually a 10v coil in series with two ballast resistors in series contained in the RF filter unit. Quote Link to comment Share on other sites More sharing options...
ruxy Posted February 27, 2020 Share Posted February 27, 2020 Have a look at the blunt end , there will probably be a letter code embossed on the can (it will also incorporate 24) , from that you should be able to establish more info. Quote Link to comment Share on other sites More sharing options...
sirhc Posted February 27, 2020 Share Posted February 27, 2020 Maybe this would be suitable? https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F372802413469 Quote Link to comment Share on other sites More sharing options...
PeterC Posted February 28, 2020 Author Share Posted February 28, 2020 I also saw this but I don't fancy a coil made pre-1963! Quote Link to comment Share on other sites More sharing options...
PeterC Posted February 28, 2020 Author Share Posted February 28, 2020 11 hours ago, ruxy said: Have a look at the blunt end , there will probably be a letter code embossed on the can (it will also incorporate 24) , from that you should be able to establish more info. On the blunt end is the following: KW 24V 0 221 103 001 and 965 in an oval. The long number is the Bosch serial but they don't make them any more. Quote Link to comment Share on other sites More sharing options...
PeterC Posted February 28, 2020 Author Share Posted February 28, 2020 18 hours ago, fv1609 said: Peter is your Bosch coil actually rated at 24v or is it rated to operate in the 24v system of your M201 ie it operates in series with a ballast resistor? The Land Rover "24v" coil is actually a 10v coil in series with two ballast resistors in series contained in the RF filter unit. Hi. The writing on the back of the coil states KW24V, so I guessing it is 24 volts. There are no ballast resistors fitted. At the moment I'm leaning towards fitting a 24v coil from a M38A1. Do you think this is suitable? Quote Link to comment Share on other sites More sharing options...
fv1609 Posted February 28, 2020 Share Posted February 28, 2020 I'm sorry I know nothing about a M38A1. I expect many people on here are using coils built 20 years earlier than 1963 without any issues. The vehicles I have owned from 1950s-60s have all run on their original coils, coils probably of better build quality than nowadays. To me it seems very strange to design a vehicle to run with a coil supplied with 24v rather than use a lower voltage coil + ballast resistor. The problem with a proper 24v coil is that it will have a primary inductance of about twice that of a comparable 12v coil. As the time constant (time taken for coil to fully magnetise) is related to the ratio of inductance to resistance, it seems better to reduce the inductance & increase the resistance of the primary circuit. Thereby ensure a more sustained voltage output at high revs. So a work around could be to choose a suitable 12v coil (suitable ie one designed for the polarity of earth your vehicle uses) measure its resistance & choose a ballast resistor of the same resistance. Your coil will then be supplied with 12v as it was designed for. Do not use the ballast resistor from a 12v system as often the coil will be designed for about 6v & the ballast resistor to match. Quote Link to comment Share on other sites More sharing options...
ruxy Posted February 28, 2020 Share Posted February 28, 2020 (edited) On a M201 - lifting the bonnet , a Bosch coil to me seems a bit incongruous - they were Frenchified , such as the Carter for a Solex , so I would expect a SEV Marchal. So has the Bosch been fitted as a near by a PO ? You should be able to quote that code to Bosch Automotive and obtain data & alternatives, however IMHO it is a supposition that it would be as originally intended . If I sift through the odd book I have - I may be able to determine. Edited February 28, 2020 by ruxy spelin Quote Link to comment Share on other sites More sharing options...
PeterC Posted February 28, 2020 Author Share Posted February 28, 2020 56 minutes ago, ruxy said: On a M201 - lifting the bonnet , a Bosch coil to me seems a bit incongruous - they were Frenchified , such as the Carter for a Solex , so I would expect a SEV Marchal. So has the Bosch been fitted as a near by a PO ? You should be able to quote that code to Bosch Automotive and obtain data & alternatives, however IMHO it is a supposition that it would be as originally intended . If I sift through the odd book I have - I may be able to determine. 56 minutes ago, ruxy said: On a M201 - lifting the bonnet , a Bosch coil to me seems a bit incongruous - they were Frenchified , such as the Carter for a Solex , so I would expect a SEV Marchal. So has the Bosch been fitted as a near by a PO ? You should be able to quote that code to Bosch Automotive and obtain data & alternatives, however IMHO it is a supposition that it would be as originally intended . If I sift through the odd book I have - I may be able to determine. The original combined Hotchkiss waterproof coil and distributor has been replaced by a previous owner with a conventional separate distributor and the Bosch coil, as shown in my picture. Quote Link to comment Share on other sites More sharing options...
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