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Installing a heater box (Non-AC)

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So unfortunately when I got my car, the original heater box was not there, and in its place was a (cheap) aftermarket AC system. I'm wanting to take it back to original and put in the correct non-AC heater box and had a few questions regarding it, since I don't really have any examples to go off of and will be starting from scratch.


Here is the box I'm looking at: https://atlanta.craigslist.org/nat/pts/d/woodstock-mustang-heater-71-73/7065837347.html#


I'm definitely putting in a new core before installing, but is there any material/diagrams out there or tips/tricks before tackling this?


Also, will I need to route new vacuum lines?

Plain Jane | 1971 F Code Coupe 302/C4 Automatic

Goin' to Town Rig | 1971 F100 Ranger XLT LWB 390FE/C6 Automatic

Commuter | 2018 Tesla Model 3 Midrange RWD

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I have a non a/c heater box from a 71 mach-1 in very nice condition for $50.00 plus shipping. I'm near Albuquerque, NM. Thanks, Ed Raver 50-5-250-5798

Box and heater core only. There are no control cables. If you want a picture just let me know.

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If your car came with AC from factory a regular heater box only will not fit. The blower motor is on the RH side and there has to be a special helmet shaped piece welded into the dash. With just heat you got fresh air vents on both sides. AC cars have only one vent on the R.H. side and non AC have a hole in the cowl on both sides.

My pics are all on crashed computer but here is some pics of my 73 factory AC unit.

Before you install the new heater core leak test it using about 15 lbs. of air pressure. I have had two that were bad out of the box and both were Ford cores. 

Also when you go back in with either type box go to hardware store and get you some 1/4" box mesh wire. Cut a piece and put between cowl seal and heater box. This will keep the snakes, mice and critters out of the box. I also put pieces of stainless steel pot scrubber pads in the two cowl drains on each side under the fender. This keeps them out of the cowl where they also love to build nests and stash acorns.

Factory AC cars have the key hole shaped cut out in the firewall for the heater hoses and AC connections to go through. Non AC has holes in different place for the heater hoses.

Controls and vents under the dash are different on AC cars.

West Coast Cougar Classics has great video on how tor repair an AC heater box. You have to be careful taking them apart they will break. When you take the trap doors out of the heater box to put new foam on support the area around the shaft as you drive it out. Once you have it out runa a 3/16" drill bit in and out of the formed area on the flat where the control rods fit. Makes it much easier to put back together. You can get foam kit form any of the mustang supplies they do not really look like original but will do better than the crumbled up stuff in there. You also have to put some strip calk in the case to seal it back up. You can make the case look new after scrubbing with Dawn then lacquer thinner and if it still need help spray satin clear on it. 

If you need more pics I can get in a couple days. 

My Bday tomorrow so lunch with sister the gal friend that evening. So will have no time tomorrow for sure.























When a man is in the woods and talks and no women are there is he still wrong??:P


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Thanks for the guide! I was able to find the relief area for the blower motor under the dash, so i'm 99% sure that my car originally came without A/C - so no fabrication hopefully.

Plain Jane | 1971 F Code Coupe 302/C4 Automatic

Goin' to Town Rig | 1971 F100 Ranger XLT LWB 390FE/C6 Automatic

Commuter | 2018 Tesla Model 3 Midrange RWD

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