HoggyN Posted March 12, 2016 Share Posted March 12, 2016 I'm having an issue with my S1 where it starts to falter after 12 miles. The first time it happened I assumed the fault lay with the coil as it got too hot to touch so I swapped it for a new Bosch one. It hasn't helped, the new coil also gets too hot to touch, so the fault seems to lie elsewhere. I can still only manage 12 miles before the engine starts to falter. Eventually it stops and will only restart if I pour water over the coil to cool it down. What could be causing this? Poor quality ignition leads has been suggested. Quote Link to comment Share on other sites More sharing options...
Tanuki Posted March 12, 2016 Share Posted March 12, 2016 Is the coil you used the right one? Where did you get it from? Does it have a Bosch part-number?? "Modern" coils are designed to run off 6 or 8 volts and work with a ballast-resistor to drop the 'excessive' voltage. I suspect your S1 doesn't have a ballast-resistor (they were a 1960s introduction...) so you're putting 12V into a coil not designed for it - which will make it get hot ! Quote Link to comment Share on other sites More sharing options...
Landy-Novice Posted March 12, 2016 Share Posted March 12, 2016 try changing plugs, points and condenser. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted March 12, 2016 Share Posted March 12, 2016 With Tanuki, most likely a wrong coil. Quote Link to comment Share on other sites More sharing options...
Ally V8 Posted March 12, 2016 Share Posted March 12, 2016 Is the coil you used the right one? Where did you get it from? Does it have a Bosch part-number?? "Modern" coils are designed to run off 6 or 8 volts and work with a ballast-resistor to drop the 'excessive' voltage. I suspect your S1 doesn't have a ballast-resistor (they were a 1960s introduction...) so you're putting 12V into a coil not designed for it - which will make it get hot ! Yup, make sure the primary windings of the coil are designed for direct 12v operation - ie, at least 3 ohm resistance... Most more modern coils are meant to run at 9v via an in line ballast resistor,so are 1.5 ohm resistance. Quote Link to comment Share on other sites More sharing options...
HoggyN Posted March 12, 2016 Author Share Posted March 12, 2016 Thanks. The first coil was from a Series 2 one from Paddocks and the second coil was a Bosch equivalent of PRC9858. Both 12v non-ballast coils. I'll measure the resistance tomorrow. Quote Link to comment Share on other sites More sharing options...
TSD Posted March 12, 2016 Share Posted March 12, 2016 If you have the correct coil, and you aren't overvolting the system (unlikely in a typical S1!), then excessive dwell angle would seem the likely culprit. Have you set the points properly? Quote Link to comment Share on other sites More sharing options...
HoggyN Posted March 13, 2016 Author Share Posted March 13, 2016 If you have the correct coil, and you aren't overvolting the system (unlikely in a typical S1!), then excessive dwell angle would seem the likely culprit. Have you set the points properly? The points were set properly at it's last service and It's probably only done 1000 miles since then. However, I'll check them tomorrow. As you say, over volting is unlikely but I'll check anyway as the voltage regulator was changed fairly recently. I've had a Google and it seems just about any electrical fault can lead to an overheating coil! e.g. Other reasons for coils overheating include a bad or missing engine ground strap, Corrosion in the distributor, bad point plate ground wire, corroded points, weak or improper (high output) condenser, large point or plug gap, high resistance spark plugs or wires, bad coil wire, bad electrical connections in the ignition circuit (anywhere HT or LT), bad ignition cap or rotor, Literally any tune-up parts not up to par. Quote Link to comment Share on other sites More sharing options...
HoggyN Posted March 13, 2016 Author Share Posted March 13, 2016 Dwell angel 55 degrees. Coil resistance 3 ohms. 12v stamped on the bottom. However, the voltage at the coil is 15.3 - 15.5 volts which is a bit high. Now adjusted to 13.9 - 14.0 It seems such a small change though that I can't see it curing the problem. Quote Link to comment Share on other sites More sharing options...
steve b Posted March 13, 2016 Share Posted March 13, 2016 try it with the dynamo/regulator electrically disconnected. Are you running -ve earth ? if so the -ve/cb terminal on the coil goes to the points. cheers Steveb Quote Link to comment Share on other sites More sharing options...
02GF74 Posted March 17, 2016 Share Posted March 17, 2016 Remember power is proportional to square of voltage, using the two minimum values, thats 15 W difference. Coils do run hot, youd struggle to hold one for long. Quote Link to comment Share on other sites More sharing options...
HoggyN Posted March 17, 2016 Author Share Posted March 17, 2016 That's true, and 15 watts extra may just tip the balance beyond what heat the coil can dissipate adequately.. I've been a bit busy since adjustingthe voltage so haven't had a chance to do a test run yet to see if it has made any difference. I may try Steve's suggestion too to isolate the ignition system from the charging circuit. Quote Link to comment Share on other sites More sharing options...
HoggyN Posted March 20, 2016 Author Share Posted March 20, 2016 Had a chance to put some miles on the S1 today. Despite towing as well, it didn't miss a beat so it looks like the problem may well have been over volting. The coil was quite warm but not so hot that I couldn't grab it and hold on to it for a minute or so, Thanks for all the suggestions. Quote Link to comment Share on other sites More sharing options...
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