Flashing dash guages

My 2005 impala started just fine this morning. Went to car wash(never made it) and the dash guage lights began to flicker, abs, air bag, battery, brake light, gas gauge went hay wire. It did this intermintantly. I checked the battery connection .. No issues ... Checked the charge it reads 14.2 steady even when flickering. Any suggestions? Ps. The car still runs smooth and continues to start just fine.

3.4 chevy impala 2005 ... 134k

If voltage out of the alternator is steady while the gauges flicker, could be a cluster, harness connection, power source, or ground problem.....