Blown fuse, Heat sensor broken or disconnected, thermostat jammed
In the dash behind the passenger door. Look for a small panel when you open the passenger door. I think the lighter fuse is fuse #1
check for accesories on the fuse box
All of the fuses are located in an interior fuse panel. On a 2004 Hyundai Elantra, this is located on the driver's side behind the little storage compartment.
The trunk light fuse on a 2003 Hyundai Elantra is located in the fuse box in the interior of the vehicle. It is on the driver's side. Look for the fuse for the dome light if the trunk light is not noted.
Yes, a main fuse is located in the Hyundai Elantra engine bay fuse box. The main fuse is used for the alternator just in case the alternator experiences a power surge. It protect the rest of the electrical components.
In fuse box under the hood
In a 2003 Hyundai Elantra, the heater fuse is located in the fuse box, which is typically found under the dashboard on the driver's side. You can access the fuse box by removing the cover, and the specific fuse for the heater is usually labeled in the diagram on the inside of the cover. If you're having trouble, consult the owner’s manual for the exact fuse designation and location.
Have you have not looked in your owners manual, its usually in there.
at the inside fuse box at the back side
I'm pretty sure the horn fuse is located in the fuse box under the hood, and not in the passenger compartment. If you look under the lid of the fuse box, it will say which fuse it is.
On a 2007 Hyundai Elantra, the horn relay is located in the engine compartment fuse box. To access it, open the hood and find the fuse box, which is typically situated near the battery. The relay should be labeled on the inside of the fuse box cover, making it easier to identify.