The evaporator core is a key component of the Nissan Frontier's air-conditioning system. The evaporator is located very close to the heater core, so replacing the evaporator is very similar to replacing the heater core in terms of reaching and removing it. Reaching the evaporator housing, however, requires the removal of multiple components in the truck's interior, not the least of which is the whole instrument panel.
Have the Frontier's air-conditioning system discharged. This is a dangerous procedure given the extreme pressure the system is under, and should only be performed by a professional licensed to work on air-conditioning systems.
Drain the coolant from the system into a clean container with the heater control set to "Hot," then disconnect the battery's negative cable. Wait a couple of minutes for the truck's airbags to discharge.
Disconnect the heater hoses at the firewall by loosening their clamps, then remove the rubber grommets where the heater tubes go through the firewall. Detach the refrigerant lines and their rubber grommet from the evaporator core.
Lower the steering column on the dashboard and remove the whole instrument panel, which includes removing the center console, all covers and trim panels, instrument cluster, stereo and heater/AC controls, airbags and steering column. Disconnect any components connected to the instrument panel's reinforcement bar (this includes at least the fuse panel), and remove the bar by unbolting it from both door pillars and the vehicle's center.
Remove the floor ducts for the heater and any other electrical connectors. Remove the powertrain control module, located near the center, by disconnecting its electrical connector and unscrewing its mounting bolts.
Disconnect the defroster ducts that are above the heating/cooling unit, then remove the evaporator core housing by removing its mounting bolts. Open the housing and remove the evaporator core.
Install the new evaporator core into the evaporator housing. Mount the housing back in place, then reconnect the defroster ducts.
Reconnect the powertrain control module, the instrument panel reinforcement bar and the instrument panel, along with all ducts and electrical connectors. Reconnect the refrigerant lines and heater hoses along with their grommets.
Refill the engine coolant (use new coolant if the old is contaminated), connect the battery cable and recharge the air-conditioning system.
