nkapphahn, I presume your heater core must be in the engine bay like the one in the instructions, correct? I've been unable to find some similar instructions that apply to a '78 F-250, with the heater core in the cab...so I haven't hardly driven the truck at all this year.

 

Actually, everything after the 4th photo in the North Country Specialties instructions is under the dash. Not sure why they removed that cover in the 1st photos unless it allows the evaporater to move farther out of the way, which is probably the case. Aside from that, everything else is under the dash - notice the carpet in the pics - and is just what I did. Some of the screws are almost impossible to see if you don't know they're there.

 

But I don't have that giant box in my engine bay. If the heater core is inside the cab on the North Country Specialties instructions, what's the deal with the big black box (that I don't have)?

 

I've never seen a Ford truck w/factory A/C that doesn't have the big black box under the hood. Afraid I can't help.

 

What is that black box, exactly?

So you're saying that nobody else with a '78 has something that looks like this:





A little bigger than I had hoped, sorry.

That black box under the dash is all one piece (you can't just remove the part under the passenger's feet). It has all the cables for the vents attached to it.

 

I stand by my earlier statement. The truck in your photos does not have factory air conditioning. It doesn't appear to have aftermarket a/c either.

The big black box under the hood houses the blower motor and other a/c related components.
I don't know how to get to your heater core. I don't have the Haynes manual anymore, and the Chiltons manual I still have is useless as usual.

 

The two hoses in the engine bay pic above and to the right of the heater core hoses are the AC hoses.

Did all 1978 F-Series trucks with factory-installed AC have that big black box in the engine bay?

 

All 73-79 trucks with factory AC had the Evaporator Case (big black box) out under the hood. The pictures shown are of a non-AC setup.
Heater core replacement on non- AC trucks is as simple as a cover behind the glove box. It's the same on trucks with dealer/aftermarket AC.

Heater core replacement on factory AC trucks requires removing the inside heater/AC air handler for sure, and possibly the evaporator case and the dashboard.
I'm not positive, though, as I've never done "just" a heater core replacement. 25 or so years ago I installed the factory AC components in 3-4 non-AC trucks including the dashboard and ductwork. The heater core was replaced while the air handler was out.

Edit: I now see the AC hoses in the 4th pic, right behind the air cleaner. That is absolutely an aftermarket installation. The heater core should be a piece of cake. It's "technically" a non-AC truck.

 

Interesting! Thank you for the information, lsrx101!

Can you tell from the pic if that looks like a non-AC under-dash?

Do you know from your install experience if the location of the AC lines in the above pic is normal for aftermarket AC installations?

 

I was editing my post toto address that when you posted.
Yes, aftermarket AC for sure. There are no "normal" hose locations for the AC lines in aftermarket installs. They would bring the hoses into the cab wherever they could find room or it was easiest. That looks as good as any.
What does your inside AC unit look like?

 

The controls? I'm not sure if it actually says "AC" or not. It has the two horizontal sliding levers for defrost and cool/warm. And the one vertical lever on the left for fan speed. The vertical lever on the right is to switch between fuel tanks. I'll snap a pic in the morning and post it.

For being build from the factory as a non-AC vehicle and supposedly having easy access to the heater core...I'm not seeing it (the access panel).

Thank you for your insights!

btw, what do the AC hoses that go through the firewall do? What do they connect to? If that's too big of a question, I understand. Just curious.

 

Your AC system may have been an "in dash" add on, likely a dealer installed unit. Much like a Vintage Air system today. Hard to say without looking at it in person how to chnge the heater core. From your pics it looks an awful lot like a standard non-AC system in your truck.
Edit: Maybe an aftermarket underdash evaporator (AC) unit is gone and the hoses were cut back behind the inst panel??

 

1973/79 F100/350 & 1978/79 Bronco: There are 3 different types of A/C, all are built into the dash. The parts do not interchange.

1) Factory installed Integral A/C is combined with the heater. The A/C controls are in the same panel as the heater controls.

2) Deluxe dealer installed A/C is combined with the heater. The two A/C switches mount to the bezel.

The HUGE dash bezel sweeps across the entire right side of the dash, covers up the original glove box.

There is a separate "hang-on" glove box, bolts to the bottom of the dash.

3) Economy dealer installed A/C is not combined with the heater. The two A/C switches mount to a panel that also contains two A/C registers.

This panel mounts into the dash to the left of the glove box.

 

Thanks Bill. I know you have posted this before and I was looking for your post to refer too!

To the person that said "Dealer AC is just as easy as non-AC trucks", I say WHAT?! I just did this a while back and it is NOT easy. ALL the AC stuff, including the evaporator is UNDER the dash and totally in the way. All the ducting and AC controls have to come out along with the heater box, etc. Then you have to loosen the screws on the passenger side and basically "tweak" the dash to get the core out. There is no room to work and it is a total pain! This is for economy dealer air. Been there and done that! What a PITA it was!

Dak

 

You have dealer added AC also, like mine.

Dak