2002 Astro - No Heat

I just bought a 2002 Astro from a dealer about 30 miles away from home, and discovered this morning that neither the front nor rear heat is working - both blow cold air. I have a meager 25% parts/25% labor warranty on the vehicle, but I'd like to try and diagnose and fix the problem myself, if possible, as dropping it at the dealer is very inconvenient for me.

Any suggestions on what to look for? Do these vans commonly have a problem that would cause both the front and rear heat to not work?

Thanks,
Steve

Have you checked the thermostat? I had an early 91 safari that the thermosat was not opening thus not giving me any heat.

I've discovered that it sometimes works... But it never "sort of" works. When it's working, it's working great, but when it isn't, it just blows cold.

The only thing that I've noticed that may indicate some kind of a pattern is that it seems to work most of the time if I turn it on while idling or driving slow. If I turn it on while on the freeway, for instance, it just blows cold.

Strange. I'm not going to worry too much about it right now, though, as it never really gets all that cold here and I have a lot of other things to think about at the moment. If I ever get it resolved, I'll come back and post the solution (for the search engines!).

try looking under the hood and follow the heater core hoses, there should b a vacuum controlled valve that can act up. this valve controls the heat buy opening/closing the water 2 the core. had the same problem on my '79 LeSabre when i first got my licence, and my dad's '93 Astro had the same problem. also try doing a flush.