1977 F150 Heater Core Replacement with AC
 

I have a 1977 F150 with the 400 motor. It has AC and a leaking heater core. I am currently getting steam from the defroster and previously could smell the sweet smell of coolant. I dont think it's far fetched to assume the heater core is to blame. I had the truck in the shop while I was out of town for the holidays and my mechanic said the heater core needed to be replaced. I have done some research and I can't really seem to find anything on how to swap it out when the truck has AC. Also, I see a lot of posts and pics of the heater core being under the dash, but as far as I can tell its under the hood, attached to the firewall. Am I mistaken? I took a picture today of what I am talking about. I am just trying to avoid more costly repairs and trying to do it myself if possible. The heater hoses connect directly to the heater core in the housing under the hood, correct? The alignment is the same as the replacement core I picked up...

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I believe that is the Blower and blower motor there. I am pretty sure that the heater core is under the passenger side dash right around the gloe box area. Please keep this thread up, I need to change my heater core too, and I would like pictures to follow because our trucks look like they might be set up similarily, I have a 78.

Today I pulled out the glove box and vent duct and got a good look in there (sorry should have snapped a picture) and I saw a radiator but it was WAY bigger than the replace heater core I picked up from O'Rielly. I was assuming that was the AC radiator/core. I just dont see where else it would be under there. Also, the distance between the hoses in the picture is identical to the replace heater core, it looks like it would just fit right in that housing.

I was giving you what I have read from variuos threads about this issue, I dont really know for sure. And like I said please post a thread with your replacement with pictures, so I can see what needs to happen.

Yep, not a problem. I'll be sure and post more pictures as I work on it. I have read that too, that it is under the dash. I was hoping someone on here might be able to say for sure. After looking into it today, I am thinking this job may be a little bit too much for me and I may have to take it back in to the shop. I'll be sure and post either way.

Okay thank you

Dont try to open the big black box undet the hood!!!

I've changed the cores in both my trucks in the last month and it wasn't that bad a job.

Under the dash, right side, pull the cover. 4 nuts and a bolt.

Pull the thermocouple and plate.

Pull the a/c evap forward. 4 screws. Use a bungee to hold it up.

Pull the heater core. 3 screws on two brackets

Install in reverse order.

There is a good tutorial with pictures in another forum. North County Specialties, I think

Here's that link: http://www.ncsi.info/autobody/heater/index.htm

That's it! That is exactly what I needed. When I was looking at it today I saw the AC evaporator, but didn't realize the heater core was underneath that. This gives me the info I needed. Thanks for the link!! Very helpful!! I'll post after I've got it done with some pictures.

Thanks again

It worked! I was able to get to the heater core and get it swapped out. To answer my original question: yes. The hoses hook directly to the heater core, however you still have to access it from under the dash. Getting everything stripped down to the AC Evaporator was a piece of cake, and I didn't run into any issues until that point. I followed the previously mentioned guide and it worked really well. When I started, I didn't understand why I needed to remove the plate on the outside of the housing surrounding the AC in/out pipes. Removing the plate allows more room to move the evaporator. I also removed a hose cradle from between the wiper blades to allow for a bit more movement. One thing I wasn't ready for was all the sharp edges. Once you start getting into it, everything is factory cut edges and nothing is rounded. when moving around the evaporator I found it to be quite sharp and I have a few dings and scratches on my hands to show for it.

The guide didn't do well with explaining how the heater core is attached, other than "3 screws and 2 brackets." Let me explain. There are two lower screws that hold a bracket horizontally across the bottom of the heater core. Those were the easy part. On the top of the core, there is a bracket that seats into a metal hook on the left side, and hinges to hold in the heater core and is secured with a screw on the top right hand side. I had problems figuring that out; its hard to see up in there. When removing it, you need to remove the screw and pull the bracket out (it will swing to the left). Mine was pretty well stuck to the rubber guard around the heater core (it had leaked and made a mess). Once I had the bottom bracket removed and the top bracket in the 'open' position the core came out easily.

My replacement core was very similar to the original with a few exceptions. The top and bottom of the core were wider/bigger than the original so the rubber guard around the core wouldn't fit on the new core. I double checked with my local parts store and they said 'that is just how they are'. I guess all that the rubber does it help with rattling and dampening. I decided to just use some weather stripping to provide that snug fit on the new core.

Getting the new core in was a breeze by this point, I had my position in the truck figured out and new what I was looking at. Obviously getting those 2 brackets and 3 screws back in wasn't easy. A few colorful words and some more scratches on my hand and I had it in.

Before I finished putting it all back together, I fired it up and tested it and it leaked a little. Like other posters, I just tightened up the hose clamps under the hood and ran it a little longer; no leaks. I also noticed that my heater fan motor wouldn't run without the relay being secured to the bottom of the dash. I am assuming it needed that ground to run. That caused me to pause until I figured that out.

Here are some pictures that hopefully can help out.

This picture is from the floor of the passenger side facing forward. The glove box has been removed, the right side duct and the heater housing have also been removed. This is a good view of the AC evaporator

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Here are some pictures of the new heater core with the weather stripping for padding:

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Good job on the weatherstripping! I reused the original gasket, but cut off the top.

I also plumbed mine up with all new hoses, so didn't fire it up to test it before putting it back together. Probably should have...

Bookmarked, just in case......

Yeah mine needs to be replaced as well, I have back flushed it and that didnt help. I tried bars stop leak, that didnt work so it looks like im gonna be using this guide soon! Thanks!

Noce job man.

I need to do this to my 76 F250, but mine needs a new blower motor too.

I just replaced the heater core on a 78 Bronco with a/c. Hardest part was gettin the cheap new heater core to fit since its a little bigger. Had to modify existing gasket and use weatherstriping. Took about a hour. Some people say it takes a lot longer. I have bucket seats so I took passenger side out.