According to my Hanes repair manual, it is under the dash attached to the firewall just beside the evaporator housing.
mercury villager heater core 2001
Inside the dashboard at the right.
In the lower part of the dashboard on the passenger side.
How much will it cost me to replace the heater core in my 1999 Mercury
There would only be a rear heater core if there was a rear heater, which I don't believe was an option.
Near the firewall behind the engine, or under the dash near the heater core.
Most likely a bad heater core
Right side
Located diretly behind the center console and it is a real pain to get to. Try buying the Haynes manual for the Mercury Villager/Nissan Quest and it helps somewhat.
Low coolant? Bad thermostat? Heater core plugged or airbound? Heat control cable not working?
Not all models had a heater control valve. If it has one it's either right in front of the firewall by where the heater hoses go in, or else under the dash near the heater core.
Instualation of a heater core on a 1999 Ford Explorer V6, how do you install the heater core.