I just recently bought an immaculate 1968 Calais sedan which has been sitting in a garage since 1975. The car has 54,000 original miles and is in fantastic shape. Just has a few issues from sitting for so long. One thing that puzzles me is that the red engine temp idiot light stays on all the time and I don't know why. It also has a gauge and the gauge reads that the engines temperature is fine. I tried unplugging the sensor in the intake but the light still stays on, even when the car is cold and there are no keys in the ignition. The only time it goes off is when I unhook the battery. Why could this be? Another thing seems to be that the interior lights are out, all of them. Nothing happens when you open the doors or turn the dimmer switch. I'm guessing this is probably a fuse? Any help would be greatly appreciated. Thanks!!

The engine temp lite is activated by the driver door pin switch that also turns on the dome lights. So check the door pin switch. Normally as the door is opened, the eng temp red light comes on to confirm the bulb is OK. I would suspect the switch is either sticking depressed and wont extend as the door is opened or the wires to it are disconnected. The switch threads into the hinge pillar. Spray some WD 40 on the switch and forcefully pull and push on it. Could be a fuse, but I assume you checked all with a test light before you posted, right??? post back with results.

Thanks for the suggestion. I checked the switches, as you mentioned and they all move freely and are in good shape. I even pulled them out to check the wiring and they appear fine. I don't have a test light. Honestly electrical work is not exactly my strong suit, which is why I posted my problem here. I get really stumped with anything to do with wiring. I tried unplugging the coolant sensors on the intake but it did not effect the light. It still stays on any time there is power to the car.

In regards to the interior lights, I took off the panel under the steering column and checked the fuses visually. I know that isn't definitive, but I didn't see any that looked bad or burned at all. Any ideas on this and the temp light issue would be greatly appreciated. Thanks!

Please, you need to buy a $5.00 test light and put one end to a piece of metal and with the key on, touch the other end to each side of a fuse. If the fuse is good the light will turn on on both ends of the fuse. If it only turns on on one side then that fuse or socket is faulty ( open) Visual inspection is a waste of time.