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Tried to jumpstart my car. It didn't start. Now afterward the car is in worse shape, there are no lights in the dash anymore when I turn the key, regardless of attempt to jumpstart. Hazard lights still work. No other electrical seems to be functioning. What could be going on?

The device used to attempt the jump start was a Schumacher charger that has a "jump start" option. "100A engine start"

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Turns out I didn't read the instructions right (heh). It says to plug the charger in then set to "jump start" wait a couple minutes till it goes from "On" to "RdY" before cranking.

https://www.batterychargers.com/sites/default/files/manuals/0099001912E-R4.pdf

I had attempted cranking it when it said "On".

It says "For severely discharged batteries, it is not recommended to crank during this time." and "WARNING: Using the Engine Start feature WITHOUT a battery installed in the vehicle could
damage to the vehicle’s electrical system. "

Seems that it did. Cause damage. Guess what the charger does is apply 100A to the battery for a minute or two, then goes back down to "low" until it detects cranking then it applies a bit more power, or some odd.

Fix was to replace the 80A "main fuse" and now it everything electrical is working OK again. It even jump starts the car fine. If done in the right order.

You can determine the right fuse by using little probes from your multimeter, if one end (and the other to ground) reads 80A and the other side read 0, that fuse's bad.

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    I'm glad that's all it was, well done getting to the bottom of it. – GdD Mar 18 at 7:58
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    I wouldn't really count a blown fuse as damage by the way – user253751 Mar 18 at 14:01
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    Thanks for coming back to post an answer for others to find! Click the little check-mark below the up/down vote arrows so others know the question has an accepted answer. IIRC, you even get magic internet points for self-accepting a self-answered question! – FreeMan Mar 18 at 18:16
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    Hope it didn't take you long to find the fuse. Good job fixing it. You got lucky...a friend of mine and I jump-started his car long ago (a Ford Probe...this was about 30 years ago, not sure if there are any Probes on the road any more!), failing to heed to warning to turn on the ventilation system for the car (the owner's manual said to turn the ventilation fan on high). We managed to fry the electronics board that controlled his car's fancy digital dashboard. Wasn't cheap to fix, either. :( It boggles the mind what engineer thought a design that could fail that way was any good. – Peter Duniho Mar 19 at 3:20
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    In some vehicles, instead of a replaceable fuse, there is a "fusible link" wire, that is much harder to change. I'm glad you didn't have that! – nexus_2006 Mar 19 at 13:05
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Check the alternator/generator and its connector wires, fusible links, relays, etc thoroughly.

If you are a technology savvy diyer check for proper working of the regulator/cut-out and diodes installed in the generator. Replacement of these components is not that costlier affair.

Best of luck!!

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