Evaporator Core / Heater Core replacement - 96 Jeep ZJ

 

 

Parts Required

 

 

Preface:

 

An unfortunate fact of owning a vehicle is that sooner or later, the most precious commodity is going to cease to work.  That's a fact.  In my case, it was the air conditioning.  In some peoples case, it may be the heater.  The problem lies in the manufacturing process of the components that control your heat and air conditioning.  In the heater cores case, coolant passing through the core causes it to expand and contract, and over time will cause the small welds on the core to break.  Corrosion also plays a roll in this process.   Air conditioning that isn't used frequently can begin to develop leaks, and in my case, the evaporator core over time developed a pinhole, causing the freon to leak out.  I tried in vain several times to recharge the system, use stop-leak compound, but finally decided it was time to replace it.

 

This job is kind of a pain.  Probably my least favorite bit of automotive maintenance besides engine swaps.  I want to say, I'm not a pro-mechanic.  Although time consuming,  this job is very possible.  An average backyard mechanic with patience and proper tools can easily tackle this job.  If your A/C or heat don't work due to bad evap core or heater core, don't suffer, just set aside some time, and do this job.  Plan on a full day at LEAST.  I got so sick of working on it, and waiting for the replacement heater core I ordered, that it took me one full week total.  I am fortunate enough to have a 60 gallon air compressor in my garage.  It came in handy several times during this job.  If you don't, be prepared to spend a little extra time wiping or possibly vacuuming the inside of the HVAC box.

 

Procedure:

 

You start out by disconnecting the negative battery cable.  You're going to be disconnecting wiring, and pulling the entire dashboard towards you.  At one point, I was sitting in the drivers seat, steering wheel dropped next to me, a few inches from my "precious body parts."  The thought of possible airbag deployment frightened me to no end.  If anything, this thought should be enough to convince you.

 

Drain the A/C somehow.  If you care about the environment (which you should,) take it somewhere to have it discharged properly.

Next, get inside the Jeep, and yank the gear shift knob straight upward.   It'll pop off.
Put the gear shift in neutral.

Put the transfer case in low range.

Pull the ebrake up.

Open the CD center console CD compartment, and remove 3 screws holding the door hinge on.   Remove the door hinge.

On the bottom of the center console CD compartment, there are 2 phillips screws.  Remove them. 

Pry the shift bezel out of the center console and disconnect light.  Set aside.

Remove the 4 phillips screws you see around the shifter.

Pry the bezel out of the transfer case selector and disconnect light.  Set aside.

Remove the center console and set aside.

Next, remove both A pillars and set aside.

Then, remove the trim running below each A pillar and along the floor and set aside.

Remove drivers side kick panel.

Remove the passenger side kick panel by removing 3 screws.

Pry the wooden colored bezels out which surround the rear wiper control and the headlight control.

Remove the screws behind those bezels that hold the lower dash on.  I can't remember how many.

Remove the outer phillips screw on the dash on each side.

Remove the screws below the driver side knee blocker panel, and the 2 screws by the steering column holding it up, set aside.

Remove the 4 screws below the glove box.

Remove the ashtray and remove the 3 screws behind it.

Remove 2 screws above the vic, and one screw below it.

Pull the VIC outward, and disconnect the wiring harness.

Remove the lower half of the dash by prying outward.  There are clips which retain them, so it'll take some force.

Use a socket to remove the 2 bolts holding in the fuse box assembly and pull it as far out as it will go (not very far.)

I have automatic climate control on my Jeep, if you have it, keep following.  If not, I don't know what you do for the next 2 steps.

There's a rubber hose on the passenger side near the center.  There are 2 screws securing it to the inside temperature sensor.  Remove the screws.

Behind that, is a wiring harness, you twist it counterclockwise to remove it.

There's a big wiring harness right next to that thing, with blue clips in it.  Remove the protective foam stuff, and disconnect this harness.

Disconnect the antenna wire.  It's looped somewhere by that big harness.

Disconnect the white connector visible in that area.

Peel the carpet back around the center by the trans hump. 

Using a socket wrench, Remove 2 nuts and 2 bolts on the drivers side holding the bracket to the floor and dash.

Between the shifter and the dash is another bracket with 2 nuts and 2 bolts, remove these.

On the drivers side of the dash, looking straight toward the firewall will be a bolt.  Remove this.

On the passenger side of the dash, up against the passenger side wall is another bolt, remove this.  It's at an angle between some wires.

Go to the fusebox, and disconnect every wire harness leading to the dash, there are I believe 9 total.  There is a little tab, and a big tab.  Push the little tab toward the center of the wiring harness while pulling up on the big tab.  This will disengage  the harness.  LABEL THESE!

On the drivers side, there's a metal bracket about a foot long below the steering column.  Remove the 4 bolts, and the bracket.

Under the steering column are 2 nuts with weird slotted washers on them.  Remove these, and drop the steering column to rest on the drivers seat.

Look on the top of the dash, where that plastic piece runs all the way across by the windshield.  Pry it up and remove it, disengaging any wiring harnesses in the way (should just be the theft indicator light.) 

Remove a bolt on each side of the dash where you removed that plastic piece. 

Remove the washers all along the dash by the windshield under that plastic piece.  They are screwed on to studs.

Have a buddy help you lift the dash upward, to remove it from the studs, then pull it forward and rest it on the seats.  The passenger side will pull out about a foot or 2, drivers side not so much.  The hold up is the mounting brackets in the center hitting the gear shift.

Look at the heater core, there is a nut with a grounding strap attached to it.  Remove the nut.

Next, get under that hood, and disconnect the 2 lines to the evaporator core.  Pry the protective metal clips off, then  insert the spring lock coupling tool on the backside of the flared part, and pull toward the front of the vehicle.  The top line is bigger than the bottom line.  If you didn't drain the A/C like I told you,  got sprayed in the face with high pressure freon but didn't die, once you are released from the hospital and regain some vision, continue to the next step.

Cap off the lines (not the evaporator core lines, the a/c lines themselves.)

Remove the clamps and disconnect the heater core hoses.  Good luck.  It's a pain in the butt.  I cut mine off, and replaced them. Get some compressed air or something, and blow in to one of the heater core hoses to flush it of coolant.

Next, remove 2 nuts, 1 bolt, and a hose holding on the coolant overflow assembly.  Remove the assembly.

Remove 2 nuts holding the PCM to the firewall, and move it out of the way.

Next, (still working under the hood,) remove the nuts holding the HVAC assembly to the firewall, there are 4 total, one under the PCM, 2 next to the PCM (one you have to remove a wiring harness tab from first to see it) and one behind the dizzy just to the right (as looking from front of Jeep) of the heater hoses.

With these removed, you can now procede back to the interior, and remove the HVAC box. 

 

Now that the box is removed, you can begin disassembling the HVAC box.  Begin by removing the phillips screws all around the perimeter.  There are I believe 10 of them. 

Next, you'll see a metal rod leading from one half of the box to the other.  Use a small flat screwdriver to pry the retaining clip away at the bottom, and disengage the rod.  It's the lower side you disengage, by where the rod is threaded.

Next, you can disconnect the wiring harnesses leading from top to bottom on the box, and move them aside.

Remove the clamps securing the heater core to the box by removing 2 phillips screws and a bonding strap.

Pull the heater core straight up and out of the HVAC box.  I HIGHLY recommend replacing it at this time .. you wouldn't want to do all this again would you?

Next, pull the HVAC assembly upward, and separate the top from bottom.  Here, you'll see the evaporator core.  If it's like mine, it's gross looking.

 

I used some compressed air to clean out the entire assembly, and the blower.  I then sprayed Lysol all over everything in there, to kill any mold or mildew.  I also sprayed Lysol on the new evaporator core to kill any existing mold or mildew it had accumulated from sitting.  Make sure the evaporator core drain tube is clear.  I transfered over as much of the black foam covering from the old core lines to the new core lines, and used hot glue to hold it on.  I also used some foam insulation type stuff to recreate the padding which the old evaporator core came with, and used hot glue to secure it.  I also replaced the heater core while I had it out. 

 

During the HVAC box reassembly, I broke one of the blend doors inside the box.  I'm not sure which one it was, but basically the door mounts to the HVAC box via a little dowel rod, shaped like a D.  The the door sits inside a little plastic mount which is controlled by a motor.  Anyway, the little dowel piece broke off the door.  Whatever kind of plastic it is didn't stay together with super-glue, so I ended up using some steel putty I got from Walmart to try to fix it. 

 

Installation:

 

After reassembling the HVAC box, I put it back in the vehicle.  I had my wife watch the holes on the firewall to help guide me on which way to move the box to line the studs up.  I then reattached the braces to the heater core, installed the ground strap and the nut to the stud.   2 minute job.

 

Next, I installed all the washers on to the studs, using a 7/16" socket wrench with universal and long extension, and a ratcheting dogbone 7/16" for the nut behind the PCM.

 

Next, I replaced the heater hoses I mentioned earlier with new hose.  I also reattached the A/C lines to the evaporator core.  Good luck with that.  Stupid Chrysler decided to make one of the hoses just barely long enough to reach the core, and once you remove the hose the first time, all that tension the A/C line had on it releases, and the line contracts.  So basically, you have to have someone use something to pry the fitting toward the evaporator core, while another person pushes the line as hard as they can toward the core to engage it.  10-15 minute job.

 

I then pushed the dashboard back in to place, again having another person handy to help guide it.  You have to sort of angle it to get it to sit properly on the studs.  I then used an impact wrench with a long extension and a swivel to reattach the nuts to the studs.  Be careful if you use an impact wrench that you don't crack the dash plastic. 

Next, install the 2 bolts on each side of the dash by the windshield.

Reinstall the theft warning light in to plastic cover, and install cover on dash.

Next, I installed the bolts on each side by the door that hold the dash on. 

Then, install the bracket, 2 nuts, and 2 bolts that hold the dash on the drivers side to the trans hump.

Next, install the bracket, nuts, and bolts that hold the dash to the center of the trans hump.

Reconnect the wiring to the fuse block, the antenna cable, and the white colored connector by the antenna cable.

Install the 2 bolts which hold the fuse block to the kick panel frame.

Install the cover to the fuse block loosely, then attach plastic the door frame to the fuse block cover.

Back to the drivers side, attach the kick panel and the door frame.

Install screws behind the VIC/ashtray.

Connect VIC wiring harness to VIC, and install 3 screws which hold it in.

Reinstall cabin temp sensor with 2 screws and one wiring harness.

Get glove box assembly, reconnect wiring harnesses (one to power outlet, 2 to cigarette lighter, and ashtray light.)

Install glove box assembly with 5 screws (4 underneath, one on far side)

Install steering collar with 3 torx drive screws.

Raise steering column, and install 2 washers underneath which hold it up.

Install brace below steering column with 4 gold colored bolts.

Install drivers side knee blocker using 5 screws.  4 under, one on the side.

Put center console in place, and use 4 screws to hold it down by the shifter.

Install shifter bezel/indicator after plugging the light harness back in.

Install lo-range indicator bezel after plugging light harness in.

Install CD holder piece in to center console and attach with the 2 screws.

Reinstall armrest with 3 small screws.

Reinstall both a-pillars.

Reconnect negative battery cable and start vehicle with radiator cap off.

Allow the engine to run with heat on full blast, while squeezing and releasing the upper radiator hose.  This will purge air from the coolant system.

Add coolant as necessary, and continue to squeeze and release upper hose until bubbles no longer appear.

Replace radiator cap.

Have A/C system vacuumed, and refill it.

Verify operation of mode selectors on heat/ac system (i.e. vent, floor, defrost.)

Verify A/C temp is acceptable.

 

Congrats, you're done.