Dead quad Answered

Louisiana 70392

You want to know about parts for sale, for this toy... yet you have told us no specific information; e.g. the name of the manufacturer, or a model number, or model name.

I mean, that is the usual method, for searching for clues on how to repair some toy. Search for manuals, or other docs published by the manufacturer. See if your favorite search engine has detected the chatter of people discussing this toy on forums.

Unless the word, "quad" is a brand name? I dunno, I tried searching for "12v quad," "kids 12v quad," and similar using DuckDuckGo.

The word "ride-on" seemed to be present in many of these links.

Actually, it was a search for, "ride-on car wiring diagram"

https://duckduckgo.com/?q=ride-on+car+wiring+diagr...

where I found a link to an existing instructable:

Specifically, Jveazey's "Easy Guide to Repair 6 and 12 Volt Electric Ride on Toys"

https://www.instructables.com/id/Diagnose-and-Repa...

Who knows? Maybe that 'ible can give you some insight into how these toys work. Or maybe you could send a PM to Jveazey,

https://www.instructables.com/member/jveazey/

and ask if he knows what is wrong with your, "12v quad that has just died"

I would follow the main wires from the battery as there should be a fuse somewhere before the power reaches anything.
With a bit of luck it is just 50 cents to fix ;)
If the actual electronics are stuffed then you can get universal controllers online for relatively few bucks.
Pay attention though to the Voltage and Ampere requirements!
In some cases you might have to replace the throttle controls together with the controller but you can get them as complete units with everything.