2001 Chrysler T&C dash lights and gauges die when turn signals are turned on (but aren't working either)

My 2001 Chrysler T&C's dashboard instrument lights dim to virtually nothing and the gauges die when I turn on either turn signal (which now don't work either).
The only thing I've done on the van recently is cleaning one of the battery terminals with baking soda and water (corrosion build-up) and the van started fine afterwards.
Any suggestions?