What's the size of the coolant heater hose?
 

I found a little bit of greeny-yellow fluid under the passenger side dash. So I figure some component of that damn troublesome automatic AC of mine has begun leaking coolant. I don't have time to pull everything apart to figure out what's leaking, so I'm just going to replumb the coolant hose (runs along the right side of the engine block) so that it doesn't go in the firewall. Can anyone tell what size the hosing is, so I can go pick some up ASAP? The outer diameter looks like an inch or so, ,but I need to know the internal diameter size to ask for. Thanks.

More than likely it's your heater core. Probably a cracked hose end.

It looks like a little radiator that has the coolant pumped through it to heat air as it's blown over it by the blower fan in your heat and AC system.

Last time I looked under there, I did notice a diaphragm-looking thing on the right side of the housing had some sort of corrosion on it, so that might be the culprit. In the meantime, I'm just going to bypass the coolant from going into the car (I installed heated Recaro seats to keep me warm in the meantime anyways). I bought a length of 1/2" hose, so I hope that's the right size.