1990 Ford Mustang Battery drain

Keep the dome fuse out and with the neg cable disconnected put the meter on dc amps 10 or 15 and run it in series from the cable to the battery and tell me how many amps it is drawing.

With the neg cable disconnected, connect one end of amp meter to neg cable and the other lead to the neg side of battery with the positive cable still attached. Get back to me

Do you have a amp meter? Usually you have to put the meter on amps then you have to rearrange the leads on the meter. The neg stays the same but the positive lead goes into a spot on the meter just for amps, have you tried that and still get 11.56amps?

Yes you need to know. You can buy a cheap meter that does dc amps. Make sure it will do atleast 10 amps. Also when testing any kind of electrical problem you need to start with a fully charged battery, if not it will give us false readings. Also with your volt meter, reconnect the battery and start the car(if the battery is charged)and check volts at the battery, you should have around 14v at battery when running or we could have a bad alternator. Ill be watching this post so keep us posted.

That tells us that there is not enough of a draw on the system to be causing our problem. Anything under.33amps is ok. Back to the original problem. Yes I think your original thought of bad cables is going to be your problem. That is the only logical answer. I just had one this afternoon on a ranger pick up and it had the same symptoms and it was the neg battery cable end. I replaced the end at the battery and all is well. Hope this helps