Non-AC heater box vs. factory heater box


New Member
Sep 10, 2003
When going from the factory AC heater box to a non-AC heater box, what all needs to be changed? I have seen a few posts in parts for sale section that have the duct work and even the glove box door included with the non-AC box. Do I have to rip the whole dashboard out of the car to do this? Is it a 3 hour job or a 12 hour job? Any wiring that needs to be reconfigured? Thanks for any tips.
do you plan on using a G-body non AC box, or are you getting one from a early 70s GM car, or making your own?

i would just block it off with a piece of metal so the firewall looks like all one solid piece, and then build a heater core boxed up with a fan to turn on for heat... that way the only thing you have going into the car is the heater lines-

i know napa sells the box[heater core with fan built into a cube], but its 150.00, thats about 100.00 too much if you ask me-

if you could find a non ac box from a G-BODY, then that would be the ultimate way of doing this-

i would just get some heavy tin and build a box, put a heater core into the box, and use your original hamster cage blower motor to produce heat/air movement...

The dashboard will have to come out. I don't remember the exact time it took to do this, because a lot of other stuff was going on at the same time. If you purchase one make sure you get the complete setup, with the glovebox and the all the cables. If you don't get the glovebox you'll have to cut your stock one up so that it will fit.
More like 24 hours.
I got to where the dash was about out, and said, yep an AL block off plate would look good there. One of these days, I'll get one of the small Hotrod remote heaters.
Finishing up this conversion on my 455 project. To bad I dont have the photos ready to post. If you dont have the engine out it can be challenging to get the A/C module out. The dash needs to come out. Easy, but you need to pull it out with the wire harness and everything. Every thing that is bolted to the firewall needs to come out. All the ducting that is screwed down to the firewall up by the windsheild needs to be changed too. On the AC delete only the two inner air ducts above the radio are used, the two outers are not used. There are two vent cables that run to the panel below the steering column. There is only one wire that runs the entire system, plugs into the same one wire connector for the AC system. IMO I prefer the heater box over a plate if you like to drive on the street as not only does it keep you feet warm when its cold it also cuts down on the noise a little as it makes a pretty good sound insulator. Oh I also figure this is a one weekend job if you have never done it before. I figure I have about 10 hours of time if you include detatilng the firewall, removing the heater module from the donor and I also redyed a replacement dash panel.

Eric Fisher
Even if you are replacing it with an 80's gbody non ac unit, you have to remove the dash? I thought there were just two bolts behind the radio area??? And the heater core has to be changed also??? I am removing ac and thinking of doing this but if the dash has to be pulled, then it isnt worth it. Anyone???

The ducts for the defrost and floor vents are different.This system also does away with the dash vent on the far right side...A blank off vent comes with this also but is not important...The whole dash must come out enough to replace these ducts..There are small screws on top of the dash at the windsheild base also....For me, getting the AC box out was the biggest chore....There is also a ground wire secured near the computer inside the car....
Just an FYI as I am in the midst of finishing up this entire conversion. In my opinion it was not a pain in the @$$ at all but more of a fun install. You learn alot by getting behind the dashboard, and having the service manual saved me time and allowed me to cleanly get rid of the wiring I wasn't using without just cutting them off and leaving wires sitting there.

Anyhow, something that you also need to get is the connector that goes from the heater box to the back of the radio. The connector on the back of the stock AC box goes all the way to the radio area. The non-AC heater box has about a 4" of wiring with a connector on the end, which from the service manual, looks like connects to another plug that goes up and above the glovebox, then back down to the radio. I am going to have to splice mine with the non-ac connector, which is fine because I have compared the pinouts etc. But me being anal, I would have liked to have had that original connector.