How do i know if my blend door on a 2008 grand marquis is working right?

I have a 1993 crown Vic and my car doing the same thing

With the car on but not started, have the heater powered off. Press floor and off at the same time, then quickly release and press auto (within 2 seconds). This will put it into self-test mode. After it finishes, it will give you codes. Those tell any problems you might have. 24 & 25 are common blend door issue codes. If you get those, your blend door stuck. Pressing defrost will end the test.

I have a 2000 Mercury Grand Marquis LS and I just recently had that fixed. What it was was a modular a big Square box kind of thing up under the dash like a little mini computer. It tells the air conditioning and the heater to blow into the car without that it doesn't work. When I raise the hood with the air conditioner on the unit was freezing ass cold but nothing was going into the car. When I turn the heater and defroster on nothing would work either. It took about 5 or 6 hours for the Workman to fix it and they put it way up under the dash in a place where you can't even get to it easily of course that's why it took him so long. But $700 later everything works fine now. Now I'm having a problem with the electrical door locks and the interior lights. When I shut the car off and lock it it keeps locking by itself over and over again but it will do it periodically and then sometimes 20 or 30 times in a row then stop for a while and do it again also the interior lights come on. I love my car otherwise I wouldn't be fixing it I just think it's a shame that all this crap has to keep happening because it's starting to piss me off royally. So I imagine I'm going to dump another $1,200 into it getting things fixed it only has 77,000 miles on it and it's a 2000 Mercury Grand Marquis LS. I should be able to put approximately 400 to 500 thousand miles on this engine without any problems with the engine it's just the rest of the stuff.

That relocking sounds like it's probably a sticking switch. Does it do the same thing if you try to lock it from the passenger door? Try unhooking the connections going to the drivers side switch, then power lock from the passenger side. If normal, your drivers switch is bad. If same thing unhook passenger switch wires and try using the drivers side switch. If it still keeps trying to auto-relock then you're past my level. You can also try testing the ohms going in and out of each switch to find a weak point. Hope this helps. Let me know results please.