R & R on a CJ7 Heater Box



Heater Box and Defroster Duct Diagram

cjoffroad thread
great ductwork pics
Sierrajeep.com Writeup
Complete Heatercore R/R Writeup
cjoffroad thread
More great pics
JU Thread
Bypassing the Heater Core
Early CJ5 Heater Mod
Convert the Rear heater from a Chevy Astro van to your CJ
Flush the Heatercore ONLY
How to flush just the Heatercore so you don't drain your whole cooling system...
CertifiableJeep.com Writeup
Good writeup Good pics
desertcj7 writeup
Heaterbox R/R w/upgrade

First things first. You can negotiate and remove the heater box without removing the dash, but it's a lot easier if you do remove the dash. The Heater Cables are especially hard to remove with the dash on, and it's a good time to replace instrument cluster bulbs and touch up the dash panel too. In fact I cut my dash under the steering wheel column to make removal and installation that much easier. I can't always find the steering wheel puller and I personally don't like messing with the horn button and the other garbage. Also, once the Steering Column Shroud goes back on, you almost don't even notice the cut any more.
The next thing I did, which again, is not necessary but makes things easier, is remove the battery and battery tray. The first view on Terry Howe's Page illustrates this how this view can help you better see what you're doing.

There are 4 bolts keeping the battery tray in the engine compartment. 3 are pretty obvious. You have 2 vertical support arms extending up from the Battery Tray to the firewall. You have to disconnect your Diagnostic connectors from the support arm as well. There's a bolt (with a F^##*@G rusty @$$ nut on the bottom) inside the tray. The 4th is mounted at the bottom of the engine compartment on the firewall and it is paired on a stud with a forward stabilizer bar. The stabilizer bar is mounted on one side with the battery tray support bar and on the other side, it is mounted to the passenger side wheel well. This is not a stud, there is a bolt on the inside of the wheel well. When re-installing the battery tray, you might want to reverse the mounting order and put the battery tray support bar on top of the stabilizer bar on the firewall stud. This will make future removal of the battery tray a bit quicker.
The best thing to do at this point is take the hoses off the back of the heater box on the engine side of the firewall. There are 3 hoses that need to be removed. Again, 2 are obvious: there is one send, and one return, but there is a small drain hose close to the bottom of the firewall, just under the back end of the blower motor. The heater box will hold on for dear life if you don't get all the hoses off before you try to wrestle it out. You don't have to remove the big air duct drainage hose to remove the heater box. If you still have the OEM hose clamps, just destroy them. They SUCK so bad, there's simply no excuse for them and I placed a curse on the foul demon that created them. I'm sure the $1.50 it costs for new hose clamps is money well spent any how.

Don't forget to disconnect the Blower Motor feed wire from the firewall side. It is pretty obvious as it is right next to the back of the Blower Motor.
On the inside, hopefully you've taken off the dash, but if not, that's ok, I won't get mad :). The heater control cables are a pain the @$$. There's probably a better way to remove them, but after popping the grommet out of it's holder on each cable, I just grabbed each cable with some channel lock pliers and unwound it from the post. It's not going to be so fun putting them back on, but getting them off was taking too much time for my miniscule amount of patience.
Before you get going on the 4 Heater Box retaining nuts, disconnect the EECU from its cradle and detach the defroster duct.
After you have disconnected all of this C R A P, obviously there's not much left holding on to your heater box. Now you can work the 4 Heater Box retaining nuts from the engine side of the firewall. My guess is they are a 7/16. I couldn't find my standard set, so I had to go with a 12mm, which was slightly too large, but it got the job done. If you took the battery tray out earlier, you're should pat yourself on the back at this point for making such a good decision. :)
Well you've about got it out now. You can get back inside the passenger cabin and give it a tug, but odds are, it's going to fight you around the EECU Mount and the Defroster Unit connection. A little encouragement is all it takes.
Remove the Heater Box from the jeep. The Plenum will not come out with the Heater Box and that's ok. Remove the Blower Motor from the Heater Box. Just FYI~ this is a great time to do the Blazer Blower Motor conversion. Looking at the back of the Heater Box, you should see approximately 15 1/4 screws around the perimeter of the panel. Remove them. There are also 2 5/16 screws holding the Heatercore retention plate. They are the 2 larger screws located just right of the Heatercore tubes closer to the middle of the Heater Box than the other smaller screws. Remove them. You'll also find one 3/8 nut on the far right side of the Heater Box rear panel, it's holding the heater door cable actuator. The actuator doesn't have to come off, but the nut does need to be removed and the cable needs to be pulled out of the clip holder before the rear panel can be taken off of the Heater Box. Also make note of the two pegs protruding from the inside of the Heaterbox through the rear panel. They are holding the door hangers in place and upon reinstall of the rear panel, you need to make sure they go back through their respective holes in the panel. Otherwise, the doors will not work appropriately.

Summary of items that need to be removed before the rear panel can be removed.
With all the screws and nuts off, the rear panel can be pulled off the Heater Box. You'll find that there is a bead of silicone or sometime of factory sealer along the edges of the panel that will fight you, but nothing a screwdriver can't help out with. With the panel off, you can see all the doors and the Heatercore, not to mention all the crap and garbage that has collected in the box over the years. Good time to get all the leaves, twigs, and acorns out. The Heatercore and its retention plate will just pull out now. Don't throw that plate away! A replacement core will not come with a new plate. If you don't pull the panel off, it can be mistaken for a part of the Heatercore and consequently get discarded.
Well you're done... Or atleast 50% done :)! Installation is the reverse of the removal procedure.

Before you put the rear panel back on the Heater Box, put a new bead of silicone on to seal the box upon reinstall, otherwise your box will leak air like a sieve, and you're going to cuss when you have to pull the box back out. John Strenk documented this pretty well in this CJoffroad thread.

Also, when you're reinstalling the rear panel, make sure the door hangers go back through the holes on the back of the panel. It is possible to seat the panel and displace the door hangers too, not good.

Take your time when reconnecting all your cables, they can be frustrating, but once installed properly you can pretty much for get about them.

Why not this time to replace your Heater Hoses as well?

If you've taken the battery tray out of your engine compartment during the Heater Box removal, the Blazer Blower Mod is a great investment and will add maybe an hour to your Heater Core R/R now that the Box and Tray are out of your way.

Hosting by WebRing.