1969 Mustang heater core replacement

Hello. You don't have to remove the dash from the car, but, you do have to do everything you would have to do to remove the dash from the car, short of actually placing the dash outside of the car. With A/C it is even more fun. You have to evacuate the refrigerant from the A/C system because you will be disconnecting the the two A/C hoses that go to the evaporator. It isn't really all that big of a deal in the sense that it isn't very complicated,but, it is a lot of work. When you remove the dash pad you'll need to remove the clock panel with it because it's attached to the dash pad from the back. First, take all of the screws out of the bottom of the clock panel and the top of the instrument cluster bezel, then remove the radio face plate and then the two lower dash trim pieces that are beside the radio. Then, if you look at the sides of the dash with doors open, you will see a screw holding a trim piece on. Remove that, then you can get to the screws holding the lower outboard ends of the dash pad. Remove them. There will also be a couple of screws going straight up, above where the radio is. Remove them. Then remove the three screws holding the dash pad that are at the base of the windshield. The dash pad should be free now. Pull it out some, so that you can unplug the clock wires, then remove the dash pad and clock panel from the car. Disconnect the speedo and remove the screws holding the instrument cluster in, unplug the connector from the circuit board, and unplug any other wires that are holding the instrument cluster in and remove the instrument cluster. You will then see a bunch of 5/16 bolts holding the metal part of the dash in, along with being attached to some braces. Remove all of those and then get the dash out of the way and remove the heater box. This is assuming that you have already had the A/C evacuated and have disconnected the hoses from the evaperator. Replace the heater core and put all of that stuff back together. Nothing to it.

Mark, I'm gonna have to throw a wrench into your project. You should research the A/C discharge and re-fill before doing the job. Your system (unless already modified) uses R-12 refrigerant; which is (I believe) hugely expensive and maybe even illegal in the U.S. Nowadays, R-134 is the preferred refrigerant. Please call around to some radiator-A/C shops for confirmation; or anyone else on this site that knows and can help. This won't affect your heater core replacement, but might keep you from using the A/C.
BTW, Veronica, for someone who professes to know only 65 and 66 ponies...well done! I've been there and done that, and you got it right!


Almost forgot; Mark, do not stint when you replace the hose clamps on the core. Buy the best you can. You surely don't want to go back in there just to address a coolant leak. In fact, now would be a good time to replace the heater hoses as well. Have fun!

Ironhorse302 said:

Mark, I'm gonna have to throw a wrench into your project. You should research the A/C discharge and re-fill before doing the job. Your system (unless already modified) uses R-12 refrigerant; which is (I believe) hugely expensive and maybe even illegal in the U.S. Nowadays, R-134 is the preferred refrigerant. Please call around to some radiator-A/C shops for confirmation; or anyone else on this site that knows and can help. This won't affect your heater core replacement, but might keep you from using the A/C.
BTW, Veronica, for someone who professes to know only 65 and 66 ponies...well done! I've been there and done that, and you got it right!


Almost forgot; Mark, do not stint when you replace the hose clamps on the core. Buy the best you can. You surely don't want to go back in there just to address a coolant leak. In fact, now would be a good time to replace the heater hoses as well. Have fun!

Click to expand...

To start with R12 is not illegal in existing systems....R12 also has much better cooling than the typical R134 replacement kits provide and will really only work to peak efficiency IF you replace /upgrade to a compressor & system that is specifically designed for R134. By the time you spend $300 for the compressor + accumulator + etc, the $40 per pound for R12 isn't so bad.....especially when R134 in a "old school" system will only cool down to about 55 degrees and R12 will easily reach 45 (measured at the duct discharge point).

Hi again. It's been a while, but, I have had the fun of replacing the heater core in a few 69s. :weeps
It should also be mentioned that you need to be careful not to bend the metal part of the dash when doing this. It's pretty weak in a couple places, and if it does get bent, things don't fit back together right.

1969 Mustang heater core replacement

Hello markrush,
I would like to offer a few thoughts on this as well.
As others have mentioned this is a LOT of work.

I am not certain I would advise you to tackle this project
unless you have some experience working on old cars.
I know that sounds rough - - and I am always in favor of people
trying new things. Heck that is how we learn

I just wanted to let you know - this is a BIG job - not a hard job
but you will run into a lot of things to do.

If you do go ahead with this job - I may strongly consider
replacing the blower motor while you are in there.

When I did the core on our 70, I DID NOT pull the instrument
cluster. check around a bit more.
Keep in mind in addition to pulling the dash pad there are a lot
of little things such as glove box, then there are the clips
that hold the defroster ducts.

Trust me - this is a lot of work - not impossible but it is pretty
big job especially if you are not too experienced/

I hate like heck to discourage people cause we all started knowing nothing - but be certain to do this once and do it right.

You are right - there are a lot of good videos out there - and if you do this job - take pictures as you go along - they will help.
LAstly - if you attempt this job - we will be here to help if you get stuck. do NOT force parts and if you are uncertain of anything
please check here before you go further

Veronica - always a pleasure to see your words of wisdom - be well my friend

Print Dad

I ordered the seal kit which was backordered. I have gotten sidetracked on windows and doors at the moment. A loose glue-in glass (for which I got good advice on a separate thread) may end up becoming a "let's do it right and clean up the insides of the doors and rear quarters" project. I'm stewing on whether to tackle the heater core myself or call in help. There are wiring issues in the dash that will need addressed, too.
Nigel, did your car have factory AC?