So my engine is siezed, but i have ways still had power to my car and the dash/radio and headlights. Well i just went to show my buddy how siezed my engine was, and it didnt go as planned. I forgot to put my ingition wires that go from the coil pack to the spark plugs back on, and attempted to start it. When i put the key in ignition, everythig lit up as usual and music came on, but when i went to turn it over, i heard a click and lost all power. Ive checked all my battery connections as well as the grounds and connections to the fuse box. Everything seems solid? Also has a brand new battery in it. Any idea? Almost like i popped a fuse but i dont know of any fuse that would cut off all power to my car? Please help lol. If i cant figure this out then theres no point in replacing the engine.
The battery had to work too hard to try to crank a seized engine, which by definition isn’t going to crank. 
Try cleaning the battery terminals.
If you are sure the engine is seized you shouldn’t try to crank the engine. You may damage parts like the starter motor you’ll need to transfer over as part of replacing the engine. The click is probably the starter motor solenoid contacts, and the loss of electrical power is b/c the starter motor was unable to turn, which causes a huge current to flow through its windings, which discharged the battery. Suggest to disconnect the battery and leave it disconnected because the starter motor solenoid contacts can weld themselves in the “on” position if the current is high enough, and this could result in an engine fire.
Even if it was a brand new battery purchased just 20 minutes before?
If you try to stop a tank with a handgun and fail, that doesn’t mean your gun is bad. It means the tank is too strong for the gun to stop.
Your engine is seized (assuming it really is). That means it’s too stuck for the battery to start.
Why did it work all the other times on a weaker battery then? Hmm
There is more than likely, a single large fuse to protect the chassis wiring feeding the car. Some have combinations of a main fuse and fusible links. Here’s one resource showing the main fuse in a Mazda 6. You don;t state year of yours but you could search on your specific year to get better info- Mazda 6 Service Manual - Main fuse removal/installation - Power system
Are you saying that after the engine seized, it cranked on a weak battery, and then you put a strong battery in, and it wouldn’t crank?
'Cause the weaker battery couldn’t provide enough current to burn out whatever it is you burnt out with the nice, new fresh, powerful battery!
Its a 2004. That link was a bit blurry and comfusing to me.
Nope. Im saying the electronics still worked on the weak battery even after attempting to start it several times trying to figure out the problem
And what could that be?
Your new battery had so much power it blew the main power fuse when you tried starting a seized engine.
You will need to replace it.
try to jump started
A 14 year old car with an engine that has seized solid, and now has chassis electrical problems? Why are you even messing with this? I am all for keeping an old car running, but it sounds like the cost to resurrect this one–even at DIY prices–will exceed the cost to buy another used car in decent condition.
Not a single rust spot on it and it has a lot of sentimental value, plus it will only run me about 1000 to get it going strong again. Only has 117k on the transmisson which has a brand new clutch in it. So a new car would be much more expensive and probably not as reliable. I was messing with it to show my buddy what i siezed engine will sound like if you try to start it because nothing ever bad happened in the past from doing this. He has a 2008 mazda 6 and thinks his engine is siezed.
Re: Loss of dashboard electrical power after failed cranking attempt on seized engine
Start by checking these three main fuses:
100 A Main fuse
40 A Key 1 fuse
30 A Key 2 fuse
Those big-amp sort of fuses are usually in the engine compartment. On my Corolla they are part of the battery + cable ass’y. Sometimes they are referred to as “fusible links”.
So both you and your buddy have Mazda 6’s of similar vintage with seized engines?
Yeah but his was a result of a shop sending him home with a coolant leak