After jump starting 2001 blazer all dash board lights/gauges flashing

After jump starting 2001 blazer all dash board lights/gauges flashing ,i used the jump start charger to restart the blazer , soon i noticed that speedometer was not working ,took the blazer fr battery change ,tech removed the red terminal while car was running to chk if alternator is ok ,and i noticed that all dash borad gauges started flashing ? replaced with new battery ,it stopped fr a while then started flashing again ?none of the gauges are working ?can anyone pls advise ,what went wrong ?and how to fix it?

Never a good idea to remove the battery cables from the battery while the vehicle is running or if the key is in the run position.

When you say flashing do you mean they literally turn on and off or the get brighter and dimmer but never go completely out.

Have you checked fuses for the instrument cluster. There is a guage fuse and a cluster fuse in the instrjument panel fuse box.

its flashing on/off ,when i start the blazer everything goes normal ,but sometimes after few minutes or latter all gauges start flickering /jumping ,and lights in dashboard starts flashing,i have checked fuses they seems to be fine

Have you noticed if the interior lights and headlights flicker as well? Have you checked output voltage of the alternator while this happens? Are you sure the battery cable ends are clean and tight on the battery?

all other lights are ok no flickering , i also ran scan on it ,it came clean? mechanic tried fiddling with some cleaner insided dash board ,flickering is gone but most of the gauges are not working , temp, fuel , spedo , and RPM is showing very high even in idle ,it means RPM is also not ok ,mech says change the dash board ? i am not sure if his advice is ok? what do u think , is there a BSM module in 2001 4X4 BLAZER LT , by any chance it got faulty? and where is the location , in fuse compartment there is no Fuse Marked BSM , the fuses markes are ECM near Engine fuse and ECM1 ????

Battery connectors are ok ,

do u think it could be Dash board cluster ?or ignition switch?

if the dash lights are flashing and the gages are jumping it probly is the ing switch same thiing happened with my 2001