I have a 2000 model F150 4.3L V6. The air that comes out of the heater does not heat up. You can barely feel it get a little warm. That temp gauge on the dash seems to be working. AC works good. I was thinking it might be low on water, but the overflow has some liquid in it.
I would love to troubleshoot it.
How does the temp selector work, is it electronic, vacuum, or manual. I assumed the hose going to the heater core is the one coming out of the top of the engine. It doesn't appear to have any type of valve or switch in it. How does this system work.
you need to research other threads out here about this concern
1st u need to check both heater hoses coming from the heater core make sure both are equal tempature in not or one is hot your core is probably plugged if bothar ehot then possibly a blend door issue.
both hoses cold check your cooling system t-stat waterpump etc,etc