Late last winter, I started noticing little or no heat blowing when I started my wife's 03 Venture. As soon as I started to drive, it would begin to heat up. When I began to slow or stop, the blower would start to blow cool air again. Dealership blew me off last year, saying "its a big van...it takes time to heat up" and claimed there was no problem. As the cold weather is working its way into the Northeast again, I have to address this issue again. Its not even hot enough on idle to defrost the windshield...the wife and kid freeze until 5 minutes after driving when the air starts to blow hot. It virtually rendered my auto start useless on cold days.

Any help with this would be greatly appreciated.

Several things :

check the coolant level to see if it's low
If it's low there is a leak somewhere , hoses , waterpump , intake manifold gasket , etc.

The thermostat may have failed .. stuck open which would not throw heat at idle.

The rad cap may be leaking ... not holding pressure

You may need to have a cooling system flush.

My wife's van also was not blowing any heat. It is also a 03 Venture. These have an interal filter in the glove box. As soon as we removed the filter, it was blowing very hot. Filters are approximately $30 to $40 depending on where you purchase it.

Mightymom!! BINGO!

We're having the exact same problem with our 2002 Venture as rpl47. So did this glove compartment filter replacementfix the problem?

Amazing that those 2 fabric filters were the problem, but they were. For anyone that encounters this problem, I replaced the 2 fabric filters located in the back of the glove compartment and the heating problem was solved. Unfortunately, this was after I had already replaced the thermostat and checked the waterpump.