Heat not working or diles

You most likely have an air pocket in the cooling system. The heater core on these vans is much higher than the engine and they can be tough to get all the air out of them.

Make sure the coolant in the radiator is full when engine is cold- also fill the overflow bottle to the top. Chock the rear wheels. Jack up the front of the van as far as you can and support with jack stands. Run the engine until it's warm and then hold the RPMS at 2000 for about 5 minutes while checking for heat inside the cabin. You may hear some funny noises like something is trying to come through the firewall forcefully! That's the air pocket moving... you might not hear this also. Once you have good heat inside, let the engine idle- if the air coming form the vents cools off after a couple minutes, the air is still there- keep doing this until the air is hot coming from the vents at idle for more than a couple minutes. Once you have good heat, turn the engine off and let the engine cool completely- at least a couple hours... you will most likely see the level in the overflow drop dramatically. Lower vehicle and make sure overflow is at COLD FULL mark.

Newer Altimas also had a similar situation in which heat would go away at idle- usually not a problem with an air pocket, but Nissan has a bulletin out on putting the correct concentration of coolant/water in the system- these cars are very sensitive to changes in coolant mixture concentration.

Nissan Scope Technician- 10 years with Nissan