78 jota charging problems

troutbishop

troutbishop

Hero member
Location
Worcestershire England
Hi all  :D 
  Having a problem with a 78 Jota which doesn't seem to be charging . I have fitted a DMC ignition removed the smaller charging coil and fitted a larger in its place I have connected the two Yellow wires from each coil to the yellow wire to the rectifier at the connector block and the same with the yellow wires with the black tracer . I don't know if the bike was charging before as it was not running when I got it .
Any ideas gratefully received .
 
Ahh the proverbial was it working before playing around or not that is always a great question...........
Have you checked that you have battery supply to the rectifier if so then
start it up and run a meter across the field wires from the alternator to see if you any output. If you are then your issue is with the rectifier if not then you have something not happening so remove and start again.
 
The Green book that came with the bike has some of the charging system text underlined in pen that's what makes me wonder . Nothing coming from either of the wires coming from the alternator but odd that both charging coils would have gone  down ? if I rev it over 2k I get about 12.5V  at the battery
 
Nothing coming from either of the wires coming from the alternator
Click to expand...

How did you measure this?  Remember this bit is AC, not DC so select voltmeter range accordingly!  Ideally, check each coil individually with engine running - should see a good voltage with moderate engine revs (more than tickover) - say 20-30volts.
 
18v for each coil, with the other coil disconnected?
If yes, then the rectifier isn't working.  If no, check the coils for resistance - measure across its wires (yellow; yellow/black), and from one wire to the iron core for each. A short on one could collapse the volts from the other

12.5v at the battery is the battery voltage only.  To charge it, you need at least 13.2
 
Cheers Rob. I hate electrics you can see an oil or fuel leak easily but not an electric leak.  18v both coils connected . I was guessing one had gone down I will have to check to see which one . I will let you know how I get on .

Once again thanks
 
Ah, if you've got voltage with both coils connected, then I reckon your rectifier isn't working.  Is it still the original stuck under the battery tray?
 
Yes Rob 18v with both coils connected where they join into one , one probe into the yellow and the other into the yellow and black, yes its still the old rectifier under the  battery tray . I can pull the one off my 3C and try it on to see if its any better.
 
troutbishop said:
Yes Rob 18v with both coils connected where they join into one , one probe into the yellow and the other into the yellow and black, yes its still the old rectifier under the  battery tray . I can pull the one off my 3C and try it on to see if its any better.
Click to expand...
Good idea try that think it will solve your problem though the poor 3C becoming a donor sounds like me at the moment........hmmm
 
You must log in or register to reply here.
Back
Top