My van now has no heat and I've searched and read through numerous threads but cannot quite pinpoint a heater problem the same as what I am experiencing.
The problem first reared its head when the fan was intermittently blowing hot or cold air, and it appeared the problem was brought on when moving the temperature control dial. When it blew hot, it was REAL hot (maybe even hotter than normal). Now, all I get is cold air at one temp regardless of the dial position. The fan otherwise seems to work normally at all speeds and air is being pushed out the vents.
The engine temperature gauge is normal and so is the coolant level in the radiator and in the overlflow reservoir. The water pump is factory original and I have no reason think it is not operating normally. I checked the heater hoses at the firewall and both are hot and at the same temperature (to the touch) as the upper radiator hose. Is it fair to assume this means the heater core is not blocked or restricted?
The problem first appeared several weeks ago and I have since swapped out the thermostat and changed coolant (Zerez G-05). This didn't solve anything although it was due for a change, anyway.
Could it be a blend door issue? I hear this is a common problem. Most blend door issues reported on this forum are for 3rd gen vans, mine being a 4th-gen. I don't know where to look to see how the blend door is actuated or how to diagnose a problem with the door. If there's an electrical connection for a motor or a vacuum line under the hood then I could use some advice on what to look for.
Finally, has anyone ever had a problem with the AC/Heater Control module? This seems to be part of the equation that controls the mix of hot and cold.