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Discussion Starter #1
I disconnected my battery after reading the thread here on problems with rear tailgates not operating correctly - my power tailgate stopped working and, what's worse, the tailgate would not lock. After reconnecting the battery, the car will not start and none of the electrical systems are working (lights, dashboard, locks). The battery shows a full charge. Is this a fuse problem?

At least the tailgate is now locked.
 

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Hmm, my first guess would be it's not really connected securely, assuming you didn't accidentally touch the wrong cable to the wrong post and cause a spark that would blow a fuse. The dealer did a few battery disconnects on our 19 and never had any issues with things not working afterwards.
 

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2015 3.6R Limited w/ES
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Hopefully you only disconnected the negative cable? If that's the case, then, as suggested, check that connection again. Make sure it's clean and tight (shouldn't move when twisted - don't over-tighten it either).
 

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If you removed both terminals and reconnected the ground (-) first, you may have blown the main fuse.
That seems to have happened to a few folks
 

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Discussion Starter #5
Only removed one. There did seem to be some oil or grease on the terminal. I'll clean it up and try again. Thanks!
 

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So.... which one? To be clear, the rule is, never mess with the positive cable unless absolutely necessary.
It's normal to have some grease-like stuff on the terminals (functions as a protectant).
 

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Normally, grease has a pretty strong film so it doesn't completely squish out when things are pushed together. That can insulate the terminals.

You want things to be clean when you tighten the battery clamp. Then after it's tight, put grease on it for corrosion. Usually doesn't make too much difference, but maybe?
 

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Here's a thread where someone blew a main fuse, with photos so you know what to look for:

 

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Discussion Starter #10
Cleaning the grease off didn't help, and since absolutely nothing electrical is working, I suspect that you are right about the main fuse. Car is in a different location from me, but I'll check it this weekend. My other half did the initial disconnection so I can't swear the he didn't accidentally make contact with the other terminal or do something else bad..
 

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ar is in a different location from me, but I'll check it this weekend.
What year, model, trim etc? Not all Subarus (if that's what it is) are the same.

How did the tailgate get locked?

Do the stop lights work when the brake pedal is pressed?

If the car does not have memory power seats, do they work?
 

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If you removed both terminals and reconnected the ground (-) first, you may have blown the main fuse.
That seems to have happened to a few folks
While reconnecting ground first is a very bad idea, even dangerous, that is for a different reason and has nothing to do with fuses blowing - in fact, it's the risk of bypassing all the protection provided by fuses if you accidentally bridge from the non-grounded battery terminal to the body (ground) with a tool. I'm having a hard time understanding how the order of reconnecting the cables to the battery could cause a fuse to blow.
 

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While reconnecting ground first is a very bad idea, even dangerous, that is for a different reason and has nothing to do with fuses blowing - in fact, it's the risk of bypassing all the protection provided by fuses if you accidentally bridge from the non-grounded battery terminal to the body (ground) with a tool. I'm having a hard time understanding how the order of reconnecting the cables to the battery could cause a fuse to blow.
Because if you connect the + first and accidently let your wrench touch ground, nothing happens. If the negative terminal is connected and you touch ground while connecting the positive you get fireworks.

Conversly if you connect the positive first, and then your wrench accidently touches ground while connecting the negative nothing happens.

Disconnection should take place in the reverse. Negative first, then positive for the same reasons.
 

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Because if you connect the + first and accidently let your wrench touch ground, nothing happens. If the negative terminal is connected and you touch ground while connecting the positive you get fireworks.

Conversly if you connect the positive first, and then your wrench accidently touches ground while connecting the negative nothing happens.

Disconnection should take place in the reverse. Negative first, then positive for the same reasons.
Yes, I understand all that, which is why connecting the ground first can be dangerous and is a very bad idea, as was stressed in the post you quoted, which also cites the example you give.

What I don't understand is how doing this could blow a fuse, regardless of whether you shorted the battery directly to ground with a wrench or not.
 

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Cleaning the grease off didn't help, and since absolutely nothing electrical is working, I suspect that you are right about the main fuse. Car is in a different location from me, but I'll check it this weekend. My other half did the initial disconnection so I can't swear the he didn't accidentally make contact with the other terminal or do something else bad..
If you remove the negative terminal first you don't need to worry about touching anything when removing either terminal.
 

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Yes, I understand all that, which is why connecting the ground first can be dangerous and is a very bad idea, as was stressed in the post you quoted, which also cites the example you give.

What I don't understand is how doing this could blow a fuse, regardless of whether you shorted the battery directly to ground with a wrench or not.
Because the sudden burst of current that gives the "fireworks" can randomly blow any fuse in its path. While you're shorting out the battery, you're also causing a surge everywhere else in the electrical system the battery is hooked up to, i.e., the car. The car's electrical system senses a sudden drop in resistance because of the external short, so a fuse blows by design to prevent a surge in more expensive components that are harder to get to and replace. If my explanation is incorrect, hopefully someone more knowledgeable can explain it better.
 

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What I don't understand is how doing this could blow a fuse, regardless of whether you shorted the battery directly to ground with a wrench or not.
Indeed. The order of connecting the cables should not blow a main fuse.

Also, shorting the positive to a ground with a tool etc., bypasses the main fuse.

There's been cases here of blown main fuses, but if I recall correctly, they were associated with reversed connections when boosting, or when connecting the car's cables to, the battery.

The 2020 (linked thread in post #9 above) is somewhat more problematic. It has two positive connecting points at the battery (see post #5 in that thread), separated by the main fuse. When working at the downstream positive post, a short to a ground would blow the main fuse.
 

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Because the sudden burst of current that gives the "fireworks" can randomly blow any fuse in its path.
But that's the point [bold added]. The current through a tool at the positive post to ground doesn't go through the main fuse, except in the newer models with the main fuse at the positive battery post.

This diagram is 3rd gen, and typical of the Subaru wiring where the main fuse is in the engine compartment fuse box.

main fuse vs battery connections.jpg
 

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Because the sudden burst of current that gives the "fireworks" can randomly blow any fuse in its path. While you're shorting out the battery, you're also causing a surge everywhere else in the electrical system the battery is hooked up to, i.e., the car. The car's electrical system senses a sudden drop in resistance because of the external short, so a fuse blows by design to prevent a surge in more expensive components that are harder to get to and replace. If my explanation is incorrect, hopefully someone more knowledgeable can explain it better.
The first sentence has already been capably addressed by @plain OM

Sorry, but the rest is not correct, either.

A dead short across the battery will indeed cause a rapid drop in the voltage (not resistance) available to the system. So will disconnecting either of the battery terminals. The rest of the electrical system neither knows nor cares about the enormous current flowing from the battery through your wrench to the chassis if you flub disconnecting the positive terminal first; all it "knows" is that the voltage has dropped, probably to near zero.

If what you say were correct, then the very act of disconnecting even the negative terminal (as you should always do first) would blow fuses. It doesn't. Nor is there any physical reason to expect it to. Reconnecting the negative last (as you should) after completing your work causes an immediate rise in voltage (a "surge" if you want to call it that). That shouldn't blow fuses, either, if the electrical system is working as designed.

As has already been noted, hooking up a battery with reversed polarity, as is done occasionally, absolutely will create havoc with the car's electrical system, including blown fuses, but blown fuses are the least of your worries if you do that.
 
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