Hey all,

Been working on various fixes lately and realizing I would likely to take another stab at fixing the air conditioning controls being stuck on defrost in my 1988 Mustang GT.

The heater core was replaced once upon a time and you can clearly tell that by the photos, but I'm curious where does the HVCB -> FCCB line (based on the diagram) between the firewall and the vacuum cluster go? I can't seem to find a good way to check if it's actually connected or damaged (even using an endoscopic camera it's difficult to tell). In my case, it is behind the glove box, and then it goes up through a small crack in some plastic near the heater core. I can't think of a good way to check this other than removing the whole dashboard (please tell me I don't have to haha).

I know the A/C reservoir canister is good as I went through the effort to swap that with a known good one, so to me I'm guessing there is an issue between the vacuum line in the firewall, and that cluster of lines that are joined together behind the glovebox.

Hoping this makes sense and that I can sort out why the controls are stuck on defrost even when selecting other options.

Project Car: 1989 Fox
Has anyone replaced fusible links that are imbedded in the wire harness connected to the stater solenoid with in-line circuit breakers. My concern is regarding the circuit protection considerations that need to be taken into account, I would build a panel with the appropriate breakers and relocate it under the fender and above the fender splash shield. This vehicle will not be a daily driver. Street summer fun driving only. Thanks. I appreciate the input.