I changed the battery in my 2002 Chevy Trailblazer last night. Car starts and runs fine, but the majority of the interior electric components are not working. I changed out the battery relay in the fuse box, but nothing changed. Any suggestions?

There are fusible links, usually located near the battery attached to the big red cable, or near the starter motor and again attached to the big main battery wire.

There are large fuses to protect the major circuits. Are you sure the cable connections are clean and tight ? Have you checked the major fuses for power, and the ground connection ?

You'll need someone to check for a battery drain.
Something like a glove box light is using electricity when everything is switched off.

Low power lean conditions cracked air intake tube GM Testing by a qualified repair person with proper diagnostic tools is the way to a proper fix , not someone guessing !

check fuse panel first for blown fuse,second check your daytime running lights come on without flickering. if problem persists- all these are affected by headlight switch- controls interior lighting and headlamps and daytime driving lights

Check for busted `fuse. This is a case of electrical grounding. Have it check by an
automotive electrician to correct the defect.

new battier and check fuses

burnt a link bar out ??

try changing the air filter ,i had a problem ,at ilde in drive my trailblazer would stall, changed the air filter now it's not stalling and got my power back ,there is a secondary air pump that i have to change ,
not sure were it is ? still not running perfect but it's running better .and my service light is on too.
i got it put on scope ,it's the pump .
not sure if this helps ,but i'm start to run in to problems too,i have a 2004 trailblazer.
i like to do fix things myself ,i hope i can.it's the cost if you know what i mean.

check the crank shaft sensor