I dont daily drive my truck anymore.. so sometimes it will sit for a few weeks or so. I decided to drive it last weekend and the battery was dead. Okay.. i guess it happens so I jumped it. Fine and dandy. Drove it for about 7 miles and let it idle for about 30 mins to make sure the battery was charged. Cut the truck off, and just out of curiosity i tried to start it again..dead. I figured i just didnt let the battery fully charge.

I also noticed my radio would stay on with the engine off key out.. Ive had the same radio (JVC KD-S25) for over a year now and this is the first time this has happened. Its wired in with one of those scosche Ford wiring harness connectors. Ive been manually turning the radio off and taking the face plate off.

I drove it around all that day and didnt have any issues starting it back up (This was on saturday) and now tonight I tried to start it and it was dead.

I have an optima red top as well.. and havent had any issues with it.

 

First id clean up the battery terminal connections and tidy them up to get good contact.

Then check the following:
Alternator field could be going down or even the regulator. I'd also check the alt. field fuse under the hood. Put a DMM on the battery when the truck is running and you should see 13.8 + volts. If you see that, then typically your alt is fine.

Next, check your battery. Batteries can hold voltage but still be dead. When you apply a load the voltage drops and amperage is decreased. Most shops have testers to see if the voltage drops when a load is put on it.



If its not the alt, then

 

The radio always has a constant power wire (to save memory and functions). However, the accessory(Red/black) wire should only come on with the ACC or ON position. I would check that the accessory relay isn't stuck. Typically when they stick, it keeps the lights on too.

 

With the truck running im at 13.6-13.9 volts according to my Edge Evo. I will have to get the battery checked out next week.. and the accessory relay that could be sticking thats in the under hood fuse/relay box?

 

My old battery was doing this, plenty of power for radio lights and all that, but when you hit the starter it dropped to 8 volts.

When I went to replace it I found the PO had put a horribly undersized one in, the interstate guy said it belonged in a civic, he was surprised it lasted as long as it did (4 years) especially with the winch. New battery and no problems since.

 

pull the radio and check the red and black wires to make sure they are not bare and touching. this would cause the radio to stay on and drain the battery. also, if your gonna leave it for a while, pull the battery to save the charge that is in it

 

The red and black touching would blow a fuse or burn up the wires if touched when the truck is in acc or on.

 

Jump started the truck this morning and drove it 30min to work. Got to work turned truck off, radio still stayed on. Took out the #1 15amp fuse for the audio and #5 relay for ACC relay. Plugged them back in and cycled the key to acc, off and even moved it in the parking lot so key was in run position and now the radio cuts off with key out engine off... wtf? Strange fluke?

 

U could get a new hot battery terminal that has a shut off to turn it on and off. So u don't have to connect and disconnect the battery u could just turn it on and off, and a battery tender would help also it puts a very small amount of charge in the battery but keeps it charged up. since u don't drive it much. Just some thought.