Hey Scotty,
I have a 2000 Honda Odyssey. The AC blows cold air but when I adjust the temperature to warm it still blows cold air. I do notice the Foot blower still blows air but it's cold. This works with the front air and passenger air. What could it be?
Does it blow hot at all, like heat cranked and ac off? If not, probably the heater core. If it does, maybe a sensor, or an actuator/mechanical failure in the thingamabob that mixes hot and cold air. Also there should be a Haynes manual for that year. It could help you troubleshoot before taking anything apart...
It does blow heat but it only works when it feels like it. It work some days other times it doesn't. It wont' swap between hot or cold when i want it too and it swaps when it feels like it.
I know for sure right now, the Front is blowing cold air, and the back is blowing hot air even though the back is set to cold.