MG Car Repair: 78 MGB GT, amp fuse, battery ignition

Question
HI, I have 78 MGB GT, everything works, except there is drain on the battery. Ignition light goes out when trying to start engine. With earth disconnected and multi meter (set to amps)across terminal and earth strap, I get open circuit. Disconnect the 35 amp fuse (supplies main beam, horn, interior lights) no open cicuit. I have replaced the battery, starter motor, alternator. I know when the car is running I get 14.5V so the alternator is charging. Now the car will not start, so I think all my sparks are going to ground. This fault has been slow to develop, rather than sudden failure. Any advice please. Nigel

Answer
Hi Nigel,
If you are getting 14.5 v at the battery at a fast idle then the charging system is working. We had a rule of thumb test that served us well in the dealerships I worked in, If a battery ran down over night or in a day or two we would remove a battery cable with everything turned off and put a 12v test light between the cable and the post and if the light turned on bright, there was a draw that can run a battery down in a day or two. If the light would not come on or was very dim it would take more than two days not running to run the battery down.
Howard