2003 TJ heater core replacement
Jeep TJ Wrangler Heater Core Replacement
Remove battery. Once the battery is disconnected the airbag capacitor will discharge after two minutes making it safe to work with the airbags and electrical connectors in their vicinity. DO THIS FIRST!
Open soft top if installed and weather/garage permits. It greatly improves the lighting.
Remove the doors. This will make it much, much easier to remove the dash and heat/vent/AC (HVAC) box later.
Remove two screws and remove the cover from the knee area below the steering wheel. Once the two screws are out, the panel snaps loose with a medium pull at the bottom corners and then the top.
Remove two screws from under the steering column cover housing and remove the upper and lower half.
Set the key switch to on. Press the small release button just under the switch and pull out the key and lock unit.
Disconnect all connectors around the steering column and also the shift lock cable. Each has a press lock of various kinds. Be patient!
Remove the bolt from the steering column joint near the brake pedal. Make sure the front wheels are close to straight ahead.
Remove four nuts that hold the steering column in place; two face up and two face forward.
Slide the steering column out taking care to not let the steering wheel turn more than 90 degrees in either direction relative to the column assembly. Set the steering wheel to center and put the entire column aside blocking the wheel so it canít roll and lose the center position. Itís not real critical as to position as the shaft is square and if you retain position within +/- 45 degrees it will be OK.
Disconnect the large connectors at left wall behind the OBD connector. Each has a jacking retainer handle. Be patient and gentle. You should not have to pull on the wires.
Remove the six torx screws that hold the dash, three at each door jamb.
Remove the glovebox.
Inside the glovebox cavity:
Remove the two nuts holding the airbag brace. You will see them inside and just above the glovebox cavity. Disconnect the large green connector that feeds the HVAC box. Disconnect the multipoint vacuum connector. Disconnect the radio antenna cable.
Disconnect the two approximately 1Ē vent hoses, one on the passenger side and one on the driver side the feed the defroster vents. They are just pushed on, but take a bit of persuasion to slide off.
Using a butter knife or trim tool remove small trim cover on top of dash immediately behind windshield, Itís about 2Ē wide and runs the width of the dash. It is held by snap-in retainers only, but can be a bit fragile and brittle, so take it easy.
Above the passenger airbag panel near the bottom of the windshield, disconnect the tiny connector that feeds the harness going up to the rearview mirror compass and light (if you have those.) The wires are in a braided sleeve.
Remove the four nuts from the studs that were hidden by the trim piece just removed.
You should now be able to pull out the bottom of the entire dash assembly and inspect to see that you havenít missed any disconnects.
With help swing the bottom of the dash back and lift the entire dash off the four studs. It weighs about 50-60 pounds and is heavier on the passenger side. This is where having the doors out of your way is a huge help.
Set the dash assembly in a safe place. Face down with a stack of towels at each end or other soft surface works well.
Remove the T handle from the automatic transmission if you have AT by grasping the T handle firmly and pulling up while rocking it left and right. It pulls free with about 20-30 pounds of force. Lift the PRNDL bezel from around the vertical piece of the shifter and rotate it 90 degrees to reveal the 10mm bolt on the right. Remove that bolt and also the one under the cup holder to permit the shifter housing to slide back. Remove the floor vent extension from the heater box by removing 3 screws and then twisting/pulling/yanking it out. Donít overdo it, but itís in there pretty snug. Folding some of the carpet back helps. This step gives some vertical clearance to help removal/reinstall of the HVAC box so that youíre not having to fight this tight clearance and risk damaging more fragile things while trying to precisely position the 30 pound heater box.
Open the hood all the way back against the windshield.
Empty the AC Freon as appropriate. R-134a is safe for the atmosphere, but discharging it openly may not be legal where you are. Wrapping a rag around a medium Phillips screwdriver works fine. Use safety glasses and bleed it off slowly to minimize loss of oil and avoid freezing burns. You may want to wear gloves.
Once the pressure is released, remove the two line connection retainers and disconnect the two lines using the appropriate disconnect tools. Bag the ends immediately to prevent moisture entering the ends. Plastic sheeting and twist ties or tiewraps works well, but you donít want to leave tape residue on the sealing areas. Be sure to cap the lines this way and if youíre keeping the evap coil, cap its lines also.
Disconnect the heater core hoses and fold them back toward the radiator.
Remove the 6 nuts on 5 studs at the firewall under the hood that hold the HVAC box in place. One stud is directly behind the battery. Two studs hold the AC accumulator in place on its bracket and also support the HVAC box inside. The last two studs are directly on center behind the valve cover and another directly about 6Ē below invisibly behind engine head. The upper stud aft of the valve cover has two nuts on the same stud, one holding the intake cowl plastic drain and then another nut behind that holding the HVAC box.
Back inside, remove the two screws holding the fuse holder in place.
The HVAC box can now be rocked toward the passenger cabin and taken out the passenger door.
Disassembly of the HVAC box requires removal of 24 screws. Two are hidden inside the cowl above the blower. Two are hidden on the bottom. The remaining 20 are on top and in pretty clear view.
Remove the vacuum hose harness and set it aside. Taking a picture first will help get the hoses routed correctly going back in. Disconnect one end of the actuator pistons, either the actuator end or the vacuum motor end, whichever comes loose easier.
Using a sharp putty knife or similar tool, loosen the foam gasket that seals the lines where they pass through the firewall. If you can get the blade edge under the adhesive tape, you can save is all for easy reuse.
Once the 24 screws are out, separate the two halves, remove the heater core and evap core and give the box a good washing. Take care to avoid wetting the blower motor and especially the electric blend door control servo under the unit. You may want to just remove the servo by removing 3 screws and the connector. Itís a bit fragile and itís easy to install with the HVAC box back in the Jeep. You can check its operation by connecting it electrically and watching it cycle when you turn the hot/cold selector once everything is all back together and connected.
Install your heater core and evap core. Hardware stores have weather stripping that works great to replace any damaged foam; closed cell wonít hold moisture and grow mold like the regular foam.
Everything goes back together in reverse and it is really straight-forward.
I laid out all the screws, nuts and bolts on newspaper and painted all the heads orange to make it easier to find everything if I ever do this again. Just a thought.
This method ends up with the least stray hardware removed. Other than the heater box itself, this method results in removing only about 25 screws and nuts.
Total time was about 6 hours including deciding to remove the doors and battery to ease the interference. If you open the top, it also makes it easy to get lots of light on the subject.
Some will disagree on this, but my pop was an AC&R mechanic and Iíve been around that all my life. Unless you leave the evap/compressor lines disconnected several days, there is no need to evacuate the system. Residual Freon will slowly evaporate for several hours and will keep the moisture out if you keep the lines capped tightly. Add a two ounce oil charge (it comes in a small pressurized Freon can) and then add Freon back into the system to achieve proper pressure. Minimize the time you have the lines uncapped to the absolute minimum and itís about 99% certain you wonít have moisture problems.
This procedure does not include routine things like details on trim removal, filling the radiator, disconnecting the AC pressure lines and other topics for which guidance is easily found elsewhere.
Take it slow and enjoy the trip.