X2 on removing the clear cover & cleaning the relay points- or at least inspecting it now & then. I had one car in that would not activate the headlight motor, said the owner. I minute under the dash with a flashlight showed the relay half full of rusty water!
His car had a decades-long build-up of rainwater at the bottom of the windshield that had rusted clear thru the cowl sheet metal and dripped directly on the relay. Fixing that car was not simple nor cheap!