MG Car Repair: alternator problems, mgb roadster, alternator problems

Question
QUESTION: I had requested help on my ignition light backfeeding the coil preventing the car from turning off with the key. I replacedd the alternator, and reversed the plug. All seemed fine. After a few days of sitting, my battery went dead again. I found the alternator to be draining my battery ever so slowly. I opened the OLD one to find the regulator to have 4 wires. The NEW one only had 2 being, yellow and black. The old one had 2 other wires which were red and white. Since the old one still works, I decided the regulator must be the problem. I ordered a new regulator with 4 wires which should arrive in a few days. The NEW alternator has the connections on the rectifier for the other 2 wires. Do you know what the other red and white wires do, and do you think the old alternator may have been from an earlier model? I have a 1977 MGB roadster 1800cc. Thanks!

ANSWER: Hi bob,
No, Lucas made the changes in the number of wires and they are exchangeable and work just fine. You should check to see if the large brown wire on the alternator is what is draining the battery. If so, you need a diode pack not a regulator.
Howard

---------- FOLLOW-UP ----------

QUESTION: I replaced the regulator,and I measure 14.8 volts at idle across the battery.The engine turns off fine with the key and no back feeding of the coil. Was wondering what the charge voltage should be. With the lights on at idle, I get 15.0 volts. Do these seem right? I'm going to wait a day or so, and watch the battery voltage to make sure it does not drop
Thanks.  Bob

Answer
Hi Bob,
14.8 is a little high but it may be ok as long as it does not boil all the water out of the battery or start burning bulbs. 13.8 to 14.5 is a norm but that some times depends on the battery and the load. If it don't get any higher at RPM you may be ok just keep an eye on it and check for the battery getting hot and bulbs burning out too much.
Howard