2008 grand prix lights dilemma

gonelf1

Suddenly a few nights ago, I start my car and have no low beam headlights, the bulbs are maybe 4 months old. While getting in and out of the car, I realized that all my interior lights are now on and won't go out, with car on or off and of course all doors closed. (Had to disconnect the battery).I had noticed a few days earlier that my heater doesn't seem to work. Blower motor is fine and my a/c works. Could all 3 issues be related and caused by a single thing? Any help would be greatly appreciated!

imidazol97

First the heater. The blower motor works, you said. When you say the AC works, that would indicate the air comes out the dash vents correctly. Are you able to change the temperature of that air with the temperature lever? That would indicate the blend door is working if so.

When you try for heat, is the air coming out the AC, the defroster vents, or the floor?

If the problem is there is no heat being added, you could be low on coolant. If you have a cap on the radiator, you can open it there, after cooling the car down, to see if the radiator is full. If you only have a coolant reservoir that's plastic and a pressure seal cap on it, check to see that it's full to the line when cool.

Otherwise you might have a blocked heater core. Look at the color of the coolant in the reservoir. It should be orange if it's DexCool. If the coolant has been changed and replaced with a different all colors coolant, it could be yellow or a green. If the coolant is a sludge-colored brwon, looking like gunk. That may mean someone added the old style, cheap, green coolant to the DexCool which contaminates it and causes sludge to form that can block small passages in the heater core.

The headlamps should have relay in the fuse/relay box that's under the hood or inside the car. Check your owners manual for the location. I believe there's a relay for the low beam and one for the high beam. That relay may have failed. Often the fuse box has more than one relay with the same part number on the top; the one for the low beam power can be switched with another one to see if that fixes the problem. The non-working relay may make the other circuit inoperative. Relays are cheap to buy at the box stores, e.g..

Problem could be in the turn signal stalk where the switch goes between high and low and the headights are turned on.

The interior lights may have a switch on the ceiling light that can be in different positions where one turns the lights on bypassing the door switch. Those would turn off after 10 minutes or so just like the retained power control for the headlights if you turn them on manually and leave them on.