AC and heater core

I think what you mean is that the blend air door is not functioning properly. Its job is to switch the flow of air between A/C and the heater core. If that is what the problem is, you may be able to bypass the heater core.

The heater core is basically a miniature radiator. Hot engine coolant goes into the heater core. The blower blows air through the system. That air is directed to run through the heater core by the blend air door. The result is (1) warm air comes out of the core and goes through your vents and (2) your engine coolant is slightly cooler than it was.

That is a very basic overview of how it works. So if you take the hose that goes into the heater core, and hook it up to the hose that's coming out of the core, you will be bypassing the core completely.

Use this guide to drain your cooling system: https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars.

Next, you should see two hoses going into the firewall (that is the wall between the engine and the cabin. They should be closer to the passenger side of the vehicle. When the engine is cold, loosen the clamp on one of those hoses. Trace that hose to its other end and remove it as well. Take that hose to the local Home Depot or Lowe's store, go to the plumbing department, and get a plumbing elbow or something so you can link the two hoses together. Then just install that piece to connect the hoses, make sure that your hoses are secure and that the clamps are tight.

You will need to add some coolant to the system. Here is a guide for that: https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars
Start at step 5.

Good luck and let us know how it goes.

Keep in mind, this is just a temporary solution. It will not fix the problem. It should help you get your A/C a little cooler (not as cold as it could be, but still cooler). And come winter, or anytime that you might need the heat on, you will have to address this problem the proper way.

If the blend door actuator is the problem it is a simple item to change on that vehicle. Open the glove box, empty it out. At the bottom there are two pins that come out and the upper stop. Then you can reach in and see the blend door actuator on the side of the HVAC case. Disconnect the electrical connector and remove the two screws. Installation of the replacement is to just reverse the process. Much easier than bypassing anything and no mess.
I only wish others were this easy.

Wow I never thought it would be that easy Steve! The last one I dealt with required the entire dash to come out. Of course that is assuming that the actuator is the problem, which it probably is.

Some are real easy, Some you spend a couple days swearing and wishing you could just burn the thing to the ground.
One big thing, if you have to dig in that far, talk to the customer first and explain that it would be a real good idea to replace the heater and evaporator core with good new replacements, especially if the thing has years on it. At the very least check them close for corrosion. It really stinks when the customer comes back a couple weeks later saying that one of them leaks and you are to blame because you touched it last. I print it right on the receipt that I explained it to them, and I will even take pictures of the cores as well as show them if they are bad and print those on as well.