I have a '97 4.6 Vitesse that has been having battery discharge problems for over a year now. I am on my second Optima battery, installed a new starter about 18 months ago, and new alternator, new ground cable at about the same time. It used to go dead (down to 9.5v) overnight occasionally, maybe 2 or 3 times a week. Then I realized that my hood was not latching on the passenger side and figured that the BeCM was "awake" all the time. Fixing that kept it from discharging for 10-12 days... now it is discharging everyday, multiple times each day. Just 2 days ago I disconnected the battery, charged it then hooked up and went to the Shell station (about 3 blocks away) to gas up... after filling up it was nearly dead again... clicked, and upon multiple tries if finally slowly cranked and started. I thought it was the starter, but when you put a multi-meter on the battery it will show between 9.5 and 12.1v so it is discharging... any ideas? (fuse box??)

 

Have you checked to see if your BECM is actually going to sleep? After about 2 min or so the "P" light on the transmission (which is very faint) should go out when the BECM goes to sleep. If your BECM is not sleeping, you might want to disconnect the RF antenna to eliminate any interference that can keep your rangie awake. I had to do this a couple months ago after my neighbors decided to install an alarm system...JERKS... Since then, all is well. BTW, my rangie gets a dead battery 10 to 12 days too. I've been told by many that is normal.

 

Yeah, a couple of weeks ago I read something on a forum somewhere that said to hook up the multi-meter to the battery, close the bonnet, lock the doors and then start timing. in about 2.5 minutes the BeCM was going to sleep... and it was fine from that time forward for about 10 days, now when the BeCM goes to sleep the drain starts... yesterday it went from 12+v to 10.1 in about 30 seconds! A good Master Tech mechanic friend of mine said that there is nothing on the vehicle that should drain it that quickly, so now I am wondering about the red top battery again. ????

 

Or (Please No!) a bad BeCM.

 

You need to measure amp draw, not voltage draw.

measure the amps and when you find the draw pull the fuse until you find the problem child.

 

Thanks Rovin4life, when I checked the amperage draw I find nothing unusual... when I open the door and "wake-up" the BeCM it goes to about 11A and gradually decreases a little as lights go out etc... then at around 2 min in goes down to .01A. I think I have another defective Red Top Optima. It does not seem able to hold a 12.7 full charge even when disconnected it drops to 12.5 almost immediately, then all the way down to 10 or 9.5.

 

Battery probably has an internal short. Disconnect it from the vehicle and perform the same tests. If it still discharges, get a new battery.

 

okay, well I charged it all night on the AGM setting on the charger. It was at 12.9v. After sitting a couple minutes the excess charge came down and it was at 12.7v, 100% charged. I hooked it back to the vehicle, the amp draw was 10.66A for about 2 min., then when the BeCM went to sleep it went down to 0.152A. The voltage on the battery went down to 12.0, then recovered partially to 12.5 when I disconnected it again and it stays there. With such a small draw on it should it not recover to 12.7? Could it be the battery just can't handle a load? I am at either 1) the battery is bad, or 2) the truck is unable for some reason to completely charge the battery (because it's an AGM??) with the alt. putting out 13.9v that doesn't seem likely.

 

Hello gents!
Please, this is a helping hand request....
As usual, the problem is battery drain; now, I've checked with the multimeter: the amperage NEVER drops under 0,57 A, which definetely drains the battery.... so bad!!
I've been waiting for half an hour after locking the car to see whether the amperage would drop to 0,02 A, but NOTHING to do, always 0,57A!
So, can you help me gents? I'm afraid disconnecting the receiver won't help....
Waiting for your precious advice.
PS Battery is almost new.

 

I forgot, any advice will be very appreciated on my email: appia1961@libero.it