what could it be that the heater is sendig cold air
Thermostat stuck wide open? If you have a temp gage it would tell you that. Could be a clogged heater core (can be a nightmare to change) or simply the air door is stuck from broken clip to the heater flapper or loose vacuum tube? Feel your hoses going to and from the heater to see if they are both hot and go from there with other items.
Search Dodge Grand Caravan Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Dodge Grand Caravan Experts