If you just had A/C worked on, the dash was removed and the motherboard might have got cracked when tech was putting dash back together, that's what happened to mine.
If your Chevy trailblazer 2004 gauges are not working, check your fuel pump.
i had this happen once on an 03 dodge minivan. the alternator went bad and the battery was going dead but had enough power to get the engine started. once i replaced the alternator and charged the battery the gauges worked again. good luck!
Lose of power or ground since all the gauges quit working.
They are probably not working because they are most likely broken.
Is it all the gauges or some? You make have to take the instrumental cluster apart. Make sure all the hardness for the gauges are all connected.
my 1998 doge ram van, all my gauges are not working
check your fuses first
You may have an electrical problem. need a professional tech to look at it. I just found out that it is a gauge cluster problem. This is not the first time I heard this as I did call the dealership and explained to the mechanic what was happening, he said and the same thing. It is not uncommon for this problem in trailblazers. If the gauges are not working, then your battery is not getting charged up.
check the ground sprats
#4 fuse blew
because it's old, stupid
Check for a blown fuse.