A pinched dash wire or damage within the bulkhead connector (the connector that links the underhood wiring to the fuse block) could also cause this. When you activate your wipers, you are sending a ground signal(s) to the motor from the switch. The TEMP light needs a ground to activate, so if there is a current path from the wiper connections to the TEMP sender wire, you'd get the light to come on with the wiper switch.