Ground fault probs..battery being drained

[AdamOhio]

I believe this is a classic prob with MG's, but maybe you can clue me in on where to specifically look for a ground fault prob im having. Keep in mind I have a new battery and the alternator is functioning just fine. My '76 MGB wont hold a battery charge for more than a day or two..im sure its a wiring problem, but if there is a specific point on the car that is common to having problems with this, Id sure appreciate a reply as to where to look. Thanks!

[KimMG]

Do you have a wiring diagram? A wiring diagram will help locate all the ground connections. Make sure the connections are clean and secure. You can use a meter to test for a power drain. Disconnect circuits one by one at the fuse box to help eliminate possible problems. How do you know the battery and alternator are good? Did you test them? New doesn't always mean good. If you don't have a wiring diagram, they can be found online at mgbexperience.com

[AdamOhio]

Well, Ive had the car for about 10 years, and every spring i have to replace a un-chargable battery... as well as recharge the new one every few days. As far as the alternator, im guessing its ok because I can run the car just fine for a few hours without it dying, and after my trips the car starts up again just fine. Thanks for the info about the wiring diagram..i dont have one and will check that link out. Thx!

[Flash75]

Try removing the alternator plug overnight and see if the battery is good the next day. If the battery doesn't run discharge with the alternator unplugged you have an internal alternator problem, probably a bad regulator diode.

If the above test is good try removing the battery ground cable overnight. If the battery doesn't drain
you have a wiring or ground problem.

If the battery is still run down hook a small test light in series with the battery positive post and the positive battery cable. Be sure all electrical devices are turned off,if you have a radio with built in memory remove the fuse so the radio doesn't turn on the light. If the light turns on brightly you will need a wiring diagram for your car. Start by removing fuses and unplugging components until the light goes out find the source of the problem.

When you store the car for the winter it's a good idea to remove the battery ground strap during storage and trickle charge the battery about once a month. A good battery will run down if it sits for several months without recharging it.

This is not a classic MG problem any more than with other cars.

Clifton

[nutman79]

sounds like a shorted diode in the alt or the brown&yellow going to the alt is hot when the ignition is off.

[MGBSS63]

Take Cable Off Battery When You Touch Cable End To The Post There Shouldn't Be Any Spark.start Diconnecting Components Start With The Alternator. You Will Find Your Problem..mgbss63....ps.wear Safety Glasses