Well today I got in my car and was going to pull it out of the garage to wash it and nothing. I just put a new Ford BXT-40R battery in about three months ago and now it is dead. I usually drive my car at least once a week. It's not a daily driver. I've had other BXT-40R batteries in my car and they have lasted about three years. That's good here in the heat. So I put my voltmeter on it and it read about 5.6V (really dead). So I took it to my Ford dealer and they just even exchanged it for another one. I checked the voltage of the replacement and it was 12.7V and the car started right up. Then I thought I'd see if the alternator was working properly so I checked the voltage with the car running and the AC on max and it read about 13.4V. So I guess the alternator is working and it was just a defective battery. Seems kind of odd but oh well. Any thoughts???

 

Do you have a shaker sound system. There is a known issue with these things going whacky and the disc changer running constantly or something like that that could drain your battery.

Try using your multi-meter while the car is off and see if there are any amps being drawn through there. There will be a slight draw from the cars computer but it shouldn't be that much.

 

Yes I have a shaker 500 system in there. I did notice when I tried to start the car that the disc changer was running for some reason and the radio was on. I never leave the radio on and I haven't used the disc player for years. Thanks for the info 07 Boss. Can you tell me simply how I check with my amp meter if there is an amp draw from the computer? Where do I put my amp meter leads on? Thanks.

 

I'm almost positive about it being the shaker system since you said the changer was running. But if you want to double check the parasitic draw on the battery, this is how I do it.

unhook negative terminal
set meter on 10 or 20 amps
one lead on the battery negative post and the other on the negative cable
When the car is in sleep mode there should only be a 25-50 milliamp draw
If there is more than that you can figure out where the draw is coming from by pulling fuses one by one and watching the meter.

 

Thanks again 07 Boss. I don't know why the shaker was on at that time but ever since then it has not repeated that problem and is off when not in use. But now I'll keep an eye on it and will check the parasitic draw like you mentioned.