Charging System Light was coming on intermittently now it's coming on everyday.

What is your question?

My husband had changed the EGR valve on our 2005 Ford Explorer and after that the charging system light would come on every once and a while and then go off. My husband changed the spark plugs this past weekend and now it is coming on every single day constantly and is very annoying. Battery and Alternator are fine because I had them checked. All the gauges on my instrument panel read normal. What is causing this malfunction and what can I do to fix it? Please help!!!