# How to replace the Heater Core on a '91 240SX



## techtalk (Jun 8, 2011)

What's up guys,

The latest mechanical conquest that I had the pleasure of claiming was replacing the heater core on a customer's '91 240. For those interested in undertaking the job by themselves then feel free to consult this guide for assistance 

1) Set the TEMP lever to the HOT position and drain the coolant.

2) Disconnect the heater hoses from the driver's side of the heater unit.

3) At this point the manufacturer suggests you remove the front seats. To do this, remove the plastic covers over the ends of the seat runners, both front and back, to expose the seat mounting bolts. Remove the bolts and remove the seats.

4) Remove the console box and the floor carpets.

5) Remove the instrument panel lower covers from both the driver's and passenger's sides of the car. Remove the lower cluster lids.

6) Remove the left hand side ventilator duct.

7) Remove the radio, sound balancer and stereo cassette deck if so equipped.

8) Remove the instrument panel-to-transmission tunnel stay.

9) Remove the rear heater duct from the floor of the vehicle.

10) Remove the center ventilator duct.

11) Remove the left and right hand side air guides from the lower heater outlets.

12) Disconnect the wire harness connections.

13) Remove the two screws at the bottom sides of the heater unit and the one screw and the top of the unit and remove the unit together with the heater control assembly. Refer to this 240sx heater unit diagram if you need assistance.

***On late models the heater control cables and control assembly may have to be removed before the heater unit is removed. Always mark control cables before removing them to ensure correct adjustment and proper operation.*

To install:

1) Install the heater assembly with retaining bolts in the vehicle. Reconnect all electrical and heater control cable connections if removed.

2) Install the left and right hand side air guides to the lower heater outlets.

3) Install the center ventilator duct.

4) Install the rear heater duct to the floor of the vehicle and all components that were removed to gain access to the rear heater duct retaining bolts.

5) Install the instrument panel lower covers, floor carpets, console box and seats if removed.

6) Reconnect the two heater hoses with new hose clamps. Connect the battery ground cable and refill the cooling system.

7) Run the engine for a few minutes with the heater on to make sure the coolant level is correct. Check for any coolant leaks and the heater system for proper operation.

8) You're done! :givebeer:


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