I suspect it is partially obscured from visibility by a bracket on the passenger side of the firewall. The low pressure port is actually on the receiver/dryer below this bracket. See the link for a video on how to get to it. (It's for a Ford Expedition, but is probably the same on your Mark).
Charging the AC on 1997 2002 Ford Expedtion F150
it is located at side of dash drivers side page 109 of your owners manual starts your fuse information the following link is the owners manual incase yours is unavailable
1998 Lincoln Mark VIII Owner Guide 1st Printing
There are several things that can cause these to fail in addition to a fuse. You need specialist knowledge to trace out the circuit and identify if it is the switches, power supply, wiring or control circuits. I suggest you take it to your local repairer or an auto electrician. I presume you have checked that the lock out switch is not on.
Your vehicle has a safety system that won't let you take it out of park unless you have the brake pedal pressed ! Your brake switch could be shorted inside causing fuse to blow !
Shift Interlock System
A brake/shifter interlock mechanism prevents shifting the transmission out of the PARK position unless the brake pedal (2455) is applied. The system consists of the following components:
an actuator activated by the key interlock assembly and brake pedal pressed input.
necessary wiring.
The system operates as follows:
The actuator is energized when the ignition switch is turned to RUN, locking the transmission range selector lever in the PARK position. When the brake pedal is applied and the stoplight switch (13480) is activated, the shift lock actuator is deactivated.
The transmission range selector lever can be moved out of the PARK position.
The ignition/shifter interlock cable (3F719) locks the transmission range selector lever in the PARK position when the ignition switch is in the LOCK position. It also requires the selector lever to be in the PARK position to turn the ignition switch to the LOCK position.
If the engine seems to be running well, the problem is not likely with the thermostat, but with the blend door in the heater control box. These have a tendency to get stuck over time. To see if the have the potential for heat, warm the engine up to normal temperature. Then under the hood, find the heater hoses. They are smaller diameter hoses (about one inch in diameter). There are two of them one runs to the heater core, the other is the return line fell both hoses. If they are warm to the touch (almost hot), then you have coolant thru the core. If only one side is hot, then you may have a clogged heater core. If there is heat on both, the problem is in either the dash controls for the heat, of the blend box under the dash.
My scanner from actron was recently updated . I don't have a specific p2c39for you vehicle but the entire p2cxx series has to do with "Oxides Of Nitrogen Exceedance". That should give you an idea. My guess is it needs a tune up. NOx is up.
Sounds like you are in for a pricey repair, replace the compressor and have the system recharged or simply unplug the power to the magnetic clutch and roll the windows down when it gets too hot inside the car.
By unplugging the compressors power supply at least the engine will not be spinning a bad compressor. The drive belt will simply spin the pulley without turning the compressor no matter what settings you choose inside the car.
Expect at least 4 or 5 hundred dollars for a system cleaning ,compressor replacement and system recharge. Chances are the compressor has now contaminated the complete system with shards of material that can possibly ruin a new compressor if the system is not totally cleaned.
