Burning out coil's/overcharging

[ims101]

Please could some one help me!! I have resently restored a 1959 948cc convertable that is positive earth. Its been off the road 10 years and befor I started the restoration it ran like a dream! I've got it back together and it looks the "dogs" but she's running a bit like a pig!! javascript:emoticon(':(')
The other day I had her running almost like befor after putting a new coil on later that day she cut out, no spark a dead coil! I put another new coil on and she's running again. On checking the charging with a volt metre at higher revs she was over charging about 15.5v I've fidled with the voltage regulator and got the charge down to 12.5v at higher revs but when you put on the lights & heater the charge drops to 11.5v??
what is the correct charging at revs? am I doing anything else wrong?
any advice please!!
Ian

[d_harris]

my immediate question would be if you have the coil wired the right way round....

[ims101]

I've got the white wire from the battery to the +ve side of the coil and the white with black from the -ve side to the contact set? is it right and will that make the differance?

[bmcecosse]

Maximum charging volts should be no more than 13.9/14.1 volts. But it should hold up to almost 13 volts with 'everything' switched on and revving away merrily. make sure the fan belt is reasonably tight. Wrong connection won't damage the coil - but it can cut the HT slightly. Make sure the 'new' coils are not designed to run at 9 volts - ie ballast wire on a 12 volt system. If you run them directly on your 14 volt system - they don't last long at all!

[minor_hickup]

If it is positive earth the white and black cable should go to the + terminal on the coil. The difference is the size of the spark the coil will deliver.

12.5volts seems too low for a fast idle, it should be peaking at about 14v

[ims101]

thanks 4 that!! the spark seems to be very good just the coil burns out very quickly (in a day!!) I'll have a nother fiddle with the regulator box and try to knock up the volts at fast idle they were 15-16v I knocked them down but sounds like too far. I won't be able to have a look till my day off on Thursday and then I'll let you know the out come and put a photo up on here. I have realy enjoyed restoring the car and I enjoy tinkering in my garage with it too I am also really really enjoying driving her too this I was most worried about because in the ten years it has taken me to do the work I have become very used to driving very modern cars which don't need any tinkering. Thanks again to you all for your help as I said I'll keep you posted!!

[Willie]

As BMC says it is quite common to be sold the wrong 'ballast' type coil if you
did not get it from a Minor specialist. Have a good look at the markings on the faulty coils to check if they were straight 12v types.

[ims101]

Well hopefully I have sorted it. It is, with out a doubt the right coil. I have changed the wire from the battery and to the point round the right way. I have checked the charging volts and altered them so it is now charging corectly and I have been out today and all seems well fingers crossed!!
Thank you all for your tips it is always good to get other oppinions so cheers.

Ian Smith

[bmcecosse]

Happy motoring! But carry a spare coil (I do) just in case.

[ims101]

yeah thanks I think that is good sound advice