Problematic 2003's

I've had my 2003 Crown Vic Sport for 4 years. I love this car, next best thing to a Marauder. Having owned Fords for over 30 years, I find them to be very dependable. However, while not a POS, my CV has had more problems than any car I've ever owned. The day I bought it, the auto HVAC just blew from the defroster ducts. The dealer replaced it. The next day, the headlights would flash off & on; bad lighting control module. Dealer replaced that. Those 2 repairs were $1K. A few months later, the door control module (!?) went out. Out of pocket: $243, and can't use my key fob anymore. I got a new code for the 5 digit push buttons on the driver's door.

Last week, a power window switch went out, as well as the power mirror switch. Replacements will arrive in about 2 days. The auto climate control is goofing up again, sending most air through the vent ducts. I hear vacuum changing under the dash, so has the control module gone bad again, or had one of the dash pots gone bad ?

I ran a Car Fax before I bought the car, and it came back clear, with me being the second owner.

I also did some research, after buying the car, and it was reported that 2003 Crown Vics/Marquis',
had the worst reliability rating. It was the first year for rack & pinion steering, and several other modifications for the Panther platform.

While I have no plans to trade the car, what more can I expect to spend money on ?

I've never been "nickle & dimed" for repairs like my Crown Victoria Sport.

The only good news is that the LCM(lighting control module) that you replaced years ago is under "recall" so you can bring your receipt back to Ford and they should give you back the money you paid for it. It was a known problem but no action was taken by Ford until the last few years when a recall went into effect, if you were having problems they replace the unit free, if you had had it replaced/repaired before then they pay you back, since the replacement was a Ford part and is still the old design, they may have to replace it anyway. A fix for the defective part was figured out years ago, Dorman makes a plug in relay part for it and others have figured out that adding an external relay in place of the little one in the LCM works much better, plus if it fails it's 1000x easier to replace it(I did this fix for my 2005 and it worked perfectly).
2003 also had soft axles, it was the first year with the new rear end(longer axle shafts) and there were issues with the steel used, axles would wear at the bearing and break if not fixed. The issues with the axle shafts were fixed and in 2005.5 cars they changed to a different(31 spline) rear differential/axle combo and had no further problems.
When it comes to switches, that could be caused by something as simple as having the window open and water getting into the switch or just dirt/dust from every day use.
The HVAC controls are fixable on your own, there are a few write-ups online about it, you have to replace some O-rings inside the unit and it works again, there are sellers on ebay(and elsewhere) that have an O-ring kit for it. This sounds kinda like what you have going on now and your car is 12 years old so it's not unexpected.
The blend door actuator(the Sport has an electric actuator) is another issue with the HVAC, it generally gets stuck on the defrost setting and the dash has to come apart to replace it, doable on your own and big money at a repair shop.