Battery drain? Car won't start!

[X3FBrian]

Long read, so thanks in advance.

Yesterday I went to start the car, and the battery was dead. Absolutely dead. It was a motocraft battery and the car had been getting slower and slower to start so I just assumed the battery went bad. After 30 minutes of charging the lights would barely light up and such, and would never turn the car over, as soon as I would turn the key all power would go off.

So I went and bought a brand new red top optima battery. Tossed it in, car cranked right up, no problem.

I did my wideband install. Tapped into fuse #5 for the power, fuse #37 for illumination and I grounded it off on one of the bolts that the fuse panel is held in with. Crawled under the car, put the sensor in and got it all calibrated.

Went to crank the car, click....click....click. What the hell? So I stuck that little charger back on the car (It had a volt read out) and it read like 11.3 or so, so I took the positive and negative cables off the battery, hit the battery terminals with some sand paper and cleaned the terminals and put it back together and boom, it cranked right up. SO I wrote it off as the terminals weren't getting the proper connection.

I also took note of the volts before I stopped messing with it. Last night the car was at 11.8 volts with the car off. I cranked the car a few times and it cranked with no problem. All is good.

I go out there today to check volts and it's at 10.0 volts. Wouldn't crank, did the whole "click....click...." then it slowly started to turn over, but wouldn't crank.

What in the world could be pulling power? The only thing that I've done to the car since it's been sitting up was install a MGW shifter and install the wideband which is 2 connections and a ground.

I took a quick video, the initial "Click" is what it did right after the WB install yesterday and wouldn't even turn over. Nothing on the car is left on.

Any ideas?

Video: Battery drain? - YouTube

 

[X3FBrian]

Charged battery a little. It got to 10.8 volts. Wouldn't crank. I pulled the harness out of the factory amps. I was at 10.78. Going to let it sit for a few hours and check. Hopefully it holds there. If not ill have to get an ammeter and do it the old fashioned way

 

[03' White Snake]

I had a bad HID ballast that would turn on by itself and drain my battery.

I was in my garage one day workin and I see one headlight shining on the wall. After some investigating, found it to be the ballast. I replaced it and has been fine since.

Electrical problems suck. Good luck.

 

[X3FBrian]

I know. I'm reading bad diode in the alternator. Faulty starter. Or bad amps.

Your car looks great btw. I have a similar car except grey with black top. Same wheels, same grounded stance.

 

[01Jes]

Your alternator is failing


Edit: how many miles on Cobra?

 

[X3FBrian]

36k. Stock pullies. For now anyways.

 

[X3FBrian]

It isn't the factory amps. After I unplugged the amps, the voltage five hours later got down to 9.4.

How could an alternator cause battery drain with the car off?

 

[04redfireRO]

Get the ampmeter out and start pulling fuses and see what circuit is active. Alternator has nothing to do with battery drain.

 

[X3FBrian]

Get the ampmeter out and start pulling fuses and see what circuit is active. Alternator has nothing to do with battery drain.

That's what I was thinking. I've read a few times people saying the alternator is the culprit. I wish I knew for a fact it was so I could go ahead and order a new one with a bigger pulley for my upper/lower combo I'm about to do. Ugh

 

[03cobra#694]

Brian, did this start after the w/b install?

 

[X3FBrian]

The original battery was dead before wb install. So I got the red top. Cranked right up. Few hours later the red top didn't have enough juice to crank again.

 

[03cobra#694]

Well damn, time to get the meter out and see if anything is pulling a draw. I'd start with the w/b myself. Electrical issues suck! Might want to get the car started and throw the meter on the battery and see what kind of juice the alt is putting out.

 

[VRYALT3R3D]

I had the same exact issue happen to me before. You have an electric draw somewhere. I replaced the alternator(twice) under warranty and it wasn`t the problem.

 

[X3FBrian]

Ah man. Don't say that. Nothing was changed other than wb install and that was done 100% correct.

 

[X3FBrian]

Just got home from work. Put the charger on the battery before I left so it was at 13 volts. Cranked the car, and it was reading 14.5 volts running. I went ahead and plugged my amps back in the car, and disconnected both power sources running my wideband. If it drops again today I'll know it isn't the WB install or something bonky with it. Car was reading 12.54 volts once the car was off and I was done disconnecting the WB.

I wanted to disconnect the alternator as well but I want to at least verify that it isn't the WB

 

[X3FBrian]

Car just read 11.2 so it is te WB. I followed the how to to a T. Where are you guys tapping into for illuminate and power?? I tapped fuse 5 for power and 37 for illumination.

 

[oldmodman]

I had a similar problem just after buying my Cobra new in 2002. It was a little electrical box that controls the "timing out" on various components after you shut off the ignition and remove the key.

I've forgotten what it was called. But if I drove the car every five or six days it would start OK. But if I didn't drive it for seven the battery would be dead.

The box was replaced under warranty and I haven't had a problem since.

I hope someone else remembers what the box is called.

 

[03cobra#694]

Car just read 12.2 so it is te WB. I followed the how to to a T. Where are you guys tapping into for illuminate and power?? I tapped fuse 5 for power and 37 for illumination.

I used fuse #27(radio) for power, and like you, #37 for lighting.

 

[X3FBrian]

It's just strange. I just got off work, car was reading 11.91 volts. Which seems normal, after sitting for 14 hours. 14 hours the other day, the battery would have been at 9 volts and no use to anyone. The only thing I did was pull all the add a circuits, looked over everything and simply plugged it all back up. Battery seems to be holding charge now. No idea. I didn't change one thing on the wiring, or placement. I hope this isn't an intermittent problem.

 

[X3FBrian]

Car is dead again, wideband was unhooked, again. So it isn't the WB that is doing it. What could pull current, on a otherwise stock car? Someone mentioned alternator, anyone else have an alternator pull power from battery as the car is sitting?

I have the battery completely unhooked from the car, and it just read 10.5 volts. Went from 12.4 to 10.5 in roughly 14 hours with no WB connected. I'm going to see if the battery will at least hold voltage by itself to rule out bad battery

If the battery check outs (holds voltage by itself) ok, I'm going to charge the battery, and pull the wires going to the alt, then hook the battery up and see if it still draws