Heater system troubleshooting

[Zzorro]

I'm troubleshooting my A/C / heater system. Symptoms:
-only get heat when it's turned all the way to high heat. No intermediate heat.
-AC does not blow cold. I know I need to recharge the system (or more maybe)
-I have inspected the "flap" and they are in good shape with the original covering sill on them and no holes. (Sent a small camera into the center duct to have a look). I thought for sure this was the issue based on my reading here and elsewhere, but it wasn't).

So? What else do I check to troubleshoot the heat? Does the AC need to work before I can confirm the heater issue? Are there sensors that need to be swapped? Or the controller?

[Meir]

The heating system in the car is very simple. Hot water from the engine is constantly circulated thru the heater core located in the HVAC box.
The only thing that controls the heat, is the position of the flaps.
I would start with replacing the control unit, as it is the easiest task.
See if you can borrow one, and make sure you are using the correct part number.
If you post your part number, I can check if I have one, and can lend it to you.
If replacing the control panel will not solve the issue, you will have to start troubleshooting the flaps motors, and the temperature sensors.

[azlvr]

Originally Posted by Meir

The heating system in the car is very simple. Hot water from the engine is constantly circulated thru the heater core located in the HVAC box.
The only thing that controls the heat, is the position of the flaps.
I would start with replacing the control unit, as it is the easiest task.
See if you can borrow one, and make sure you are using the correct part number.
If you post your part number, I can check if I have one, and can lend it to you.
If replacing the control panel will not solve the issue, you will have to start troubleshooting the flaps motors, and the temperature sensors.

There's a valve that controls water flow also.