My Heater is not working

Sounds like blend door control failure. The problem is that one book says that it's a cable controlled item, another says it's electronic even with a manual control.
BUT because you say you have a slider I'm going with it being a cable.
From reading the various items it appears that you might be able to reach the end of the cable that moves the blend door if you removed the glove box and reach up to the top of the heater plenum and find the cable. Then you could tell if it's that end or the control head end by moving the lever as you feel the cable. If the cable moves but the lever doesn't it's the adjuster clip that's failed. If the cable doesn't move it's in the control head. That requires you to drop the steering column and remove the dash trim panels to remove the control.

Hi there,

with the engine hot and the heater controls on hot, feel the two heater hoses going into the cabin, they both should be about the same Temp, if not the heater tap is not on, check this first.

Mark (mhpautos)

Change the thermostat to start with, those symptoms are classic stuck closed thermostat, hopefully that'll help

I would say it is the thermastat, the lack of heat makes me think diferent, how is the fluid level? Check the belts.