Key left on; Now having electrical problems

[CheepComanche]

Yesterday I accidentally left my keys in my Jeep with the ignition on all day. Of course the battery was completely dead (no power at all) But now after jump starting it I’m having this issue where sometimes when I turn the ignition on I have almost no power. Like the battery is dead but it’s not. When the truck does have power and starts, it has really bad idle fluctuation. I worried that leaving the ignition on all day fried something. Could this have damaged the ecu? Also, as a result of this, my head unit no longer functions properly. Half the buttons don’t work

[eaglescout526]

I would look into the plug for the ignition switch and see. Maybe that’s melted more and causing all sorts of issues. Can’t imagine it damaging an ECU. Just voltage through and through. But I definitely can see it melting that connector and causing no connectivity at a couple terminals. 

[Pete M]

weird.  have you scuffed/cleaned the contact surfaces at the battery terminals real good?

[CheepComanche]

I used this and an excuse to buy the Jeepcables big 7 upgrade. But my battery terminals are clean and tight. I’ll take a look at the ignition switch plug tomorrow morning, but so far I can’t see anything wrong so I'm kind of hoping that the big 7 upgrade will take care of whatever the problem is. I also noticed the lights dimming when the hit the brakes which sounds like a big connection issue somewhere. My main fear is that the problem is something I can’t see like the ecu. 

[Eagle_SX4]

The ignition switch plug would be something to look at.

 

If your lights are dimming when you press the brake it could just be a coincidence that your alternator is dying or on its way out. Check voltage on the battery when running. It should be about 14 volts with a properly functioning alternator.

[CheepComanche]

Thanks! I’ll be sure to check that too. My alternator is about a year old but that doesn’t mean it’s good.

[gogmorgo]

What did you do to jump start it? If booster cables were hooked up backwards it can do interesting things, blow the diodes out of the alternator, pop fuses… I only know this because I’ve had it happen to me so no judgement if that happened.

 

My first thought was battery terminals. Having a battery go completely dead does sometimes cause corrosion on the terminals. The brown wire at the ignition switch is also a strong possibility. If the blower motor was going, as voltage goes down and a motor slows down, current through a motor goes up, and it will find any weak spot in the circuit.

[pizzaman09]

Did you actually replace the battery?  A battery that was taken down to zero power can easily short out causing all sorts of annoyance on the electrical system.

[CheepComanche]

I did get a brand new battery. Just a standard lead acid group 58 from Costco. I used a jump pack to start it and I definitely had the positive and negative correct. Since I’ve had some time to mess with it, I'm pretty sure my problems are coming from the battery terminals. They are clean and tight, but if I move them I can get the truck to do the weird things I talked about originally. It’s weird to me that battery terminals could cause such problems but I believe I have found the issue. Once I’ve got my jeepcables upgrade done, I’ll know for sure!

[pizzaman09]

The battery cables can be very corroded in the inside.  Due to moving them around while swapping out the battery could be breaking down the old cables. 

Please update us with how the new jeep cables upgrade works out.