The Dumbest Mistake I've Made: Putting a Battery on Backwards

I have been enjoying my Focus ST trouble free for two months now until I noticed the battery getting weaker when it sometimes failed to start the car on the first try. I took it to the Costcorp store, it tested bad and  I bought the new battery. It was a long day and I was just trying to get home throwing the battery in when I noticed the battery terminals on the battery were reversed. I figured the battery in there was just more bad voodoo from the previous owner. I rotated the battery around so it should've been the same and tried to just get it over with in the parking lot. When I put the positive terminal on I realized my error with a large arc of electricity. All the lights turned on and the horn rang out. It was under a second but it was bad enough. We got a..second new battery in there correctly and amazingly the electronics all seemed to work with the ST's keyless entry. But it would not start. 

I came back the next day and push started the car and took it across the parking lot to Pep Bros. They replaced the starter and main fuse but now every time you turn on the AC compressor it blows a fuse. I'm living in an apartment now with no place to work on the Focus. 

What I ask of the Elders of Grassrootery: What else have I likely broken in this scenario? 

Dunno, but don't feel too bad. We've all done stuff like that.

I mean I've done my share of dumb things with cars but this has to be the worst for when I was trying to fix something and save some money in the process. Definitely took a couple steps back on this one.

I'm always very careful when hooking up a new or moved battery (every time I attach a terminal, I check for a stamped-in positive or negative symbol close to it) because I know you can ruin a wide range of electronics and electrical parts that way, starting with the ECU...you're lucky so many components survived.

Similar scenario.  Jumped the car with a batter pack crossing the terminals/wires.

Blew one of the bigger fuses which put it in limp mode.

Grabbed the fuse out of another example of the same then waited a few days on e-bay for a replacement. 

Ac is grounding out somewhere, likely internal in the compressor. Take the harness clip off the compressor and try to use the AC with the car running. Does it blow? If it doesn’t, you know it’s in the compressor. If it does, you know it’s in the wiring or relay. 

My sister put diesel fuel into her 1974 VW Beetle.  Don’t feel bad. 

Datsun310Guy said:

My sister put diesel fuel into her 1974 VW Beetle.  Don’t feel bad. 

I did that to my big block 73 Cheyenne. Ran for about 3 seconds.

I’ve done it too. Blew the main fuse in my Miata. Humans, we make the mistakes.

Floating Doc said:

Datsun310Guy said:

My sister put diesel fuel into her 1974 VW Beetle.  Don’t feel bad. 

I did that to my big block 73 Cheyenne. Ran for about 3 seconds.

On the road trip I just took, I tried to put the diesel nozzle in but it was too big. Lucky me that they've started making them like that, I was real close to stranding myself there.

Don’t feel bad no one got hurt. I have done stupider things. There wasn’t a place like GRM to admit to it back then.  

Exhibit A ( because I am sure you could use a chuckle at this point) 

Disconnect HT leads from plugs and flop them over the fender. Lean over said leads and the fender while someone cranks the motor over. 

Of all the places to get zapped that is about the worst. 

dean1484 said:

Exhibit A ( because I am sure you could use a chuckle at this point) 

Disconnect HT leads from plugs and flop them over the fender. Lean over said leads and the fender while someone cranks the motor over. 

Of all the places to get zapped that is about the worst. 

.......ow

In reply to dean1484 :

Having caught an electric fence with my armpit, I just doubled over in pain reading that. 

I hooked a deep cycle battery up to the ancient dumb charger once, but it didn't seem to do any damage in the second the charger was plugged in. 

Good luck with the modern car full of electrical doodads and widgets. 

I’ve also done this and blown a main fuse. 80 amp fuses aren’t easy to find at 1am. 

Yeah, I put a quart of what I thot was oil in my 73 Vega. It poured like water.....and it was.

Caught it before I started it.....

Do not beat yourself up. Pretty much all of us have done stuff like this.

Rog

Antihero said:

dean1484 said:

Exhibit A ( because I am sure you could use a chuckle at this point) 

Disconnect HT leads from plugs and flop them over the fender. Lean over said leads and the fender while someone cranks the motor over. 

Of all the places to get zapped that is about the worst. 

.......ow

It puts a bit of spring in your step for a while. 

Re: "fix" maybe you get lucky and it's all fuse related; they're relatively cheap, you might consider replacing all of them as a "preventative" step - that said, I have no idea how many fuses are in an ST.

I know a lot of things are circuit board related in the newer cars, so that would scare me a little bit. 

One thing about working on cars is something will humble you someday. Either it's a mistake or something brutally hard.

Who needs an ego anyway? Lol

When I worked at the zone we had a lady come in that had the dealer hook her battery up backwards, she had all worlds of hell with it, and I don’t think ever got the radio or a/c working right again. I believe she traded it in and passed the headache on to some other sucker. 

I had had the battery quit on my rsx in the midst of moving to a new job and almost let the dealers lot boy hook up a jump box to it backwards. Lucky for him I was watching and stopped him from wrecking it, although I would have liked to have the Acura dealer owing me a favor at that time as I ended up trading the car in not long after. 

Compressor clutch circuits usually have a clamping diode. If you burned it up it's possible it could be shorting the circuit now. You can check for resistance from the fuse socket to ground. Right now it's probably close to zero. If it's still close to zero when unplugged at the compressor clutch I'd go looking for where that diode is. 

Had a detailer with a huffing issue (Car washer who snorted upholstery cleaner) reverse the cables jump starting his car.  The battery burst into flames, he disconnected the cables, closed the hood, and drove off with flame licking from under the hood and the paint bubbling.  He was so stoned he didn't notice, didn't pay attention to us yelling at him.  He called in the next day, and was amazed that I knew he wasn't coming to work because his car burned.