96 Dodge 2500 Van 318 V8. AT.front and rear air/heat 265,000 miles. This morning the heater would not put not any heat, yesterday it was fine. outside temp about the same. The engine temp was about mid-range as always. The hose going it to the front and the one to th rear will get hot to touch but the other hose the return will be cool. There is a valve on the hose line going to the core this valve does not move. It has a vac line on it and there is a very small vac on this line. What does this valve do and could this be the problem. The van does no over heat and runs about mid-range or the gage. The system has never been flushed. If I put the fan on low there will be a small amount of warm air.
Tanks
