I have an 89 300ci. and every other day my battery is dead. I can't figure out why. I have a new cd player rather than my old am radio, but the problem started before I even touched the radio. I even tried replacing the alternator. If any of you have ever had a similar problem and figered it out let me know.

Thanks

 

If you've replaced the alternator, and your stereo isn't big, which you've said....

Clean the battery terminals with a wire brush. Reconnect them and make sure the connection is good.
Have the battery tested. If its bad, replace it. A bad alternator will kill a battery, and vice versa. I recommend Interstate or Die Hard. Don't even think about the wal-fart "N"ever-starts.

If those don't do it for you, I'd say you have a drain...probably a small short somewhere. You'll have to get the multi-meter out and hunt. The drain probably is not large enough to blow a fuse, so you could pull them one by one to find the right circuit.

 

thanks I'll Try all of that

 

Go to Fordfuelinjection.com and research alternators, or search here for the difference between 2nd and 3rd generation alts. There is more than one alternator available for your truck. If your alternator is connected to the charging circuit via two large plastic plugs,and it has a visible external fan just under the pulley then you should upgrade to a different and better output alternator.
Do not buy a lifetime warranty alternator from your basic auto discount store, it will likely die in a year. See a professional starter/alternator shop to have a heavy duty part installed, or at least try NAPA or a dealer if you have the big bucks.
Battery life is 5 years max, and when the battery goes bad is usually just goes bad, there is no coming back the next day. That is why I am preaching new alternator.
Like the other people said..clean your terminals. Put axle grease or vaseline on the terminals to keep them corrosion free.

 

Disconnect your ground from the battery and put a test light between batt- and the cable. Everything has to be turned off, door closed and hood light off. If the light comes on, you have a draw. Pull fuses one at a time until the light goes off and that will tell you which circuit is at fault.

 

don't forget the master cylinder brack pressure switch tends to shortout on these trucks. if you haven't had the recall done, disconnect it.

 

Make sure the under hood light is off and your glove box light is going off! Those will kill a battery if there staying on.

 

Have you tried simply disconnecting the battery (both terms) in the evening when you park it, then reconnecting in the morning. this is also an easy way to determine if it's a battery drain vs battery prob.

Is the battery dead, as in nothing works, or it just won't crank but the lights and the radio still work?. Then it might be a stuck starter solenoid.

Don't forget to check the battery to starter cable(s) . They may have hidden corrosion whcih can sap your amps, and more so when cold. Cut and peel a little insulation about 6 inches away from the battery and see if there's discoloration. Don't forget to tape it up after.