CroDalmatinac

Mine used to to this and I changed my head unit to a Pioneer AVIC Z1.

No problems ever since.

P.S. I had the shaker 500.

jwog666

i have replaced 2 smart junction boxes in 04-06 mustangs for this concern. the sjb wasnt powering down. take it to a good dealer and have them perform a parasitic draw test to confirm.

tongy89

Got the same problem also. Been battling with ford for a long time now about it. I have been through several batteries and made them replace the head unit for the shaker 500. Still didnt fix it though. I have also tried turning the radio off before letting the car sit and it still was completely dead in 4 or 5 days. I started dealing with the service manager about it now so we will see if he will do anything about it or not.

Bmr4life

I had a 1990 4 cyl mustang that was parked outside my grandma's place in detroit while I was in Atlanta for college. I'd come home once or twice a year and would drive it around and never once did it need a jump. Battery was a diehard or something from sears. Car easily sat for 9-10 months one time. Hot summers, freezing winters with the car being covered by 2+ feet of snow.

Car had power everything, but no alarm of any kind.

odiaz

I don't htink this problem is unique to Ford or such a mystery. If you don't drive the car often and have electrical devices (such as an alarm or some newer radios) the devices will slowly drain the battery while the car sits. If you don't drive the car long enough to fully recharge the battery, it will only partially charge and during the next period of inactivity it will dis-charge further. At some point, it discharges to the point where it does not have sufficient power to start the car.

A trickle charger definitley helps if you don't drive your car very frequently. These trickle chargers are fairly inexpensive and will slowly charge the battery while the car sits. I've used one on every single collectible car i've owned.

The other solution is to install a quick disconnect for the negative teminal but I don't find this as an acceptable solution these days. In the old days, it was not that big of a deal to disconnect the battey during periods of inactivities becasue there were few devices that needed to have power when the car was off. But, these days, disconnecting the negative terminal will potentially reset your radio's preset stations, the time, and more importantly, you'r car's computer.