I would like to know where is the ground point for the warning cluster because the clock is playing, sometimes on, sometimes off, sometimes dim??

 

Thats called old solder. You gonna need to resolder the points on the board or get a new one.

chris

 

What he said. This problem is rarely due to grounding problems, but almost always cold solder joints in the idiot light cluster. Pull the cluster apart and resolder all large joints. While you are in a soldering mood, do the same to the CPU.

Soldering help:
http://www.aaroncake.net/electronics/solder.htm

 

The gnd for it has a designation. It's called gnd 17 and is a part of a gnd cluster called JC-03. It's location is behing the dash as almost shown in the jpg that is attached.

And again, your problem most likely does not lie there.