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Weird electrical problems

Car is a 2013 Ford Fiesta SE. Hatchback if it matters.

So, I’ve been noticing weird electrical problems in this car for a few months now. Once a check engine light came on along with some odd performance issues, and I took it to AAMCO to get a free diagnostic scan. It came back with a list of problems a mile long. Guy thought it was the battery that was going bad because all of them could be traced to a problem with the battery. I went and got the battery tested and it was totally fine.

Then, a day later, the check engine light goes away along with the weird performance issues I was having. Absolutely bizarre. Historically the car does weird things with the horn when the weather gets wet. It’s like wet weather makes the horn weaker, and at times I’ve even lost the horn entirely. But when it dries up, the horn comes back, full strength over a couple days.

Now, this is going on as I was driving back from my girlfriend’s house. I take great care of this car and I have spent about $3,000 in repairs since buying it for $4,200 in 2013. It was a repo, but there were no accidents. I got two vehicle history reports to make sure. My guess is, once it was about to be repoed, the guy decided to ignore the maintenance on it. As a result I’ve had to give it a lot of TLC. It had 139000 miles on it when I got it, but I’ve put about 20k on it. New clutch, new belts, new water pump, new spark plugs, engine oil flush, never missed an oil change and use high milage oil. I even got the throttle body cleaned out. I take excellent care of this little thing. I’m really concerned. I can’t afford more expensive repairs.

Anyone got any idea what’s going on?
VIdeo is attached with me demonstrating the problems. Again, I’ve not seen it do this before. It’s like the whole electrical system is taking a dump or I’m entering silent hill.

Take it to an auto parts store like Autozone, they will read the codes for free. Then post the codes here, format is P0123. Then we might be able to offer some suggestions.

Your electrical system has a major short, by the sound of it.

Low battery voltage is a common cause for multiple codes. You may have intermittent battery and charging system failure. I would start by making sure all wires and cables that pertained to battery and charging system are clean and don’t need replacing.

The trouble may be due to a problem within the alternator, causing excessive AC ripple voltage. To see if that is correct you can disable the alternator by removing the fuse to it or disconnect the wire connector to it. If you work on the main output lead be careful with it since it is HOT to the battery. Take a test drive and see what happens then. If that doesn’t change things then I would check out the grounding system for a problem with it.

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WOW

Very possible, due to the horns location, it may fill with water, car may be missing a splash shield

I am having a hard time following your original post . How do you buy a 2013 vehicle in 2013 for $4200.00 . Also with that many miles on it so the dates must be wrong . Weak horn when wet , I can’t even remember the last time I used my horn . Going to Amoco was a mistake or any chain type shop for that matter.
I suspect you bought a flood vehicle and a good shop should be able to give a opinion if that is possible.

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Those are the symptoms of a failing body control module.

https://moduleexperts.com/5-common-symptoms-failing-body-control-module-bcm/?gclid=EAIaIQobChMIyPjt09fx5AIVZv_jBx2wgAlvEAAYASAAEgIytfD_BwE

Tester