i put some 99 si gauges in my 98 civic hx and the hot and cold temp gauge doesent work do u know what can be the problem

 

Try plugging in your old cluster to make sure it still works on there. If the problem persists, it's most likely a problem with the cluster itself. It's 100% plug and play, so it's not a wiring issue by any means.

If it is the cluster itself, the part is relatively cheap:

http://www.slhondaparts.com/br...1-L01
78130-S01-L01 - METER ASSY., FUEL & TEMPERATURE - $28.86