Temp and fuel gauge wiring

[RaysK20]

Here is the deal, the temp gauge and fuel gauge were working just fine up until a few days ago. Now when you you turn on the head lights the temp gauge creeps all the way to full hot, and the gas gauge drops to quarter tank even when its full. You can turn the truck off and when you restart it the temp gauge returns to normal for a few until it goes full hot. The gas gauge has quit reading anything now but a solid half tank. I am not very good at wiring, but not hopeless. Anybody care to point me in a direction here. The truck is a 73 K20 for the record. Thanks for any help.

[BLE 'BURBAN]

Start by checking ALL grounds on the vehicle; at the tank, the H/L switch, every wheres inspect, clean, and reconnect.

[RaysK20]

I just got done cleaning the grounds under the hood above the head lights and the ground for the fuel tank. The only other ground I could find under the dash was mounted to the Ebrake bracket. Where does the light switch ground? So far no changes. Is there a fuse that controls the tank gauge? All the fuse look good though.