99 Astro Heater Problem

The heater on my '99 Astro isn't working. The AC works well and the blower motor does work when the heater is turned on but it only blows cold air. I've not seen any evidence of a leak.

Is there a relay or switch somewhere that allows the hot water to flow to the heater core?

Where is the heater core located?

Any other things I need consider.

Thanks much for your help.

Dave

Have you check the level of Anti-freeze in your rad? Or had work done on the van that would require the removal of the anti freeze?
You may have a air bubble trap in you heater core. Fill up rad to about a 1 inch below the top, then run engine with rad cap off for 5 minutes while the engine circulates the anti-freeze this will allow the system to burp. Best not to do this on your driveway, because sometimes when it burps it spits out anti freeze.

I took the radiator cap off and ran the engine for about 10 minutes. I didn't get any perceptible "burp". I took the hose off of the output of the heater core and had hot water flow there so I must be getting flow through the core. My fan blows but still getting only cold air from whatever vents I select.

There must be a door somewhere that permits the air to flow over the heater core. That would seem to be the problem. I'm not sure where this might be located though or what opens/closes it. Anyone have any suggestions?

Thanks!