2001 Park avenue that has no dashlights,tailights,dashlights,backup lamps or marker lights. Checked the fusebox under the hood and found one that was blown. It is a 25amp fuse labeled as the park lamp fuse. Put a new fuse in and it blew right away. I have check all of the other fuses and lights looking for a short to ground but have not found anything yet. I even unhooked some of the lights and it still blows the fuse. I am wondering if something in the headlight switch is bad. I also have no dashlights. The headlights work as well as the turn signals brake lights and flashers. Need help with what to look for next. I am trying to fix the rig for my dad who is
getting ready to go on a roadtrip.

I would disconnect all the light bulbs effected and see if the fuse still blows.
Then one by one start to put the bulbs back in and see if one causes the fuse to blow and you may then have an indication of a socket or short to ground problemo confirmed.
Al the of the rear taillights are under one connector to make it easier to diagnose.
Did u also check fuses in drivers area and under the rear seat?

if it blows before you turn the switch on you have a short to ground on the wire that goes from the fuse to the switch. diagram says orange wire through ip fuse panel to light control module

The fuse only blows when I turn on the switch. I even tried to put a 30 amp fuse ih and the lights worked for a few seconds then blew it too. I have looked at all of the lights and the bulbs and all looks good. I was going to try and get to the junkyard tomorrow and see if I can try another headlight switch. Is there another module or something that controls all of the circuits that I am missing?

yes. the headlight just tells the bcm what to turn on. thats why your lights flash when you hit unlock on the clicker. i highly doubt it would be the switch itself. id probe all the external light'* power wires and check for a ground on the positive wires. if you get a hit, look in areas open to the elements on that particular lights harness.

also, try unplugging the harness going to the trunk lid. with those wires moving every time you open the trunk you could have busted a wire in that harness. happens alot on the W bodies.

raising fuse values is a good way to start your car on fire. other than that look like jason says with a meter

Still working on the Buick. I haven't been able to find the park lamp relay. The owner'* manual doesn't show one but I have found a few wiring diagrams online and it shows a relay in the rear fuse panel under the seat. Also wondering if any of the modules under the dash could cause the problem.

most of the stuff is under the rear seat on those, and thinking of that you do like jason said and look for shorts on the positive side? those are really susceptible to leak damage to wires because everything goes on the body floor and if there is any water the wires and components are in it

yeah. there is a ground on the right side of the trunk, behind the carpet for the lights, and one near the fusebox under the seat if i remember correctly. dont bother going to the fusebox under the dash. its for the main componets. abs/ traction control etc.

as for the park lamp relay, i cant find any trace of one on my alldata account.

I have unhooked the front lamp connections and the tail lamp connections and the lamp control module and the park lamp fuse still blows. I am still leaning towards the headlight switch but have some more testing to do. Getting frustrated with this lovely machine. Going to unhook a few more things in hopes of isolating the problem.