[candiver]

I have a 2005 Astro with front and back heat. I had the same problem, and had the cooling system flushed etc, but still had no heat in front, but lots in rear. The problem was in the vacuum operated heater valve located on the firewall, connected to the heater core. The little door which diverts the hot water had come loose from the valve, and was floating freely within the valve, blocking the hot water from entering the heater core. Replacing the heater valve assy did the trick. You can test this by removing the heater valve and bypassing the lines. If you get heat after bypassing the heater valve, you know that you've found the problem.

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