Help cracking open lights

whats the best way to remove the screws holding these together? I cant get the screws to budge. I'm guessing they are stainless steel screws into the pot metal housing. Do I just soak them with wd40 or pb blaster a few days in a row and keep trying to turn them? I need to replace the bulbs from 24v to 12V for the back of my M715 and get rid of the plastic trailer lights the fire dept. put on there.

yup.. let them soak for a little while. if that does not work, tap them with a hammer the shock may bust them loose. if that dont work a little heat should do the trick.

Plan on a long frustrating journey. This has been a problem since Adam and Eve. If you ever do get them out, antisieze them before reassy. For those that buy new metal composite lights, take the screws out and antiseize them before you use them or else. Try an impact driver before you kill the screw heads.

If all else fails, cut the screw heads off, lift the cover and use a wisegrip on the screws. About 3/8 of an inch will protrude with plenty of space to grip. The thread is 10-24 if you need to run a tap to clear the holes...

Soak as much of the threads with a penetrating oil of your choice; WD-40, Kroil, PB Blaster to name a few. Let it work a few days, not just a minute or two.
Heat from a heat gun isn't a bad idea but stay away from a torch to keep from melting the zinc casting.
A trick I learned when I was just starting out is to get the screw broken loose by SLIGHTLY TIGHTENING it first; you'll hear that distinctive soft "click" when it releases. Tightening the screw is twisting it in the thread's strongest direction and once it breaks loose it should be freed up enough to come out. IF it still turns hard then apply more penetrating oil (this time you don't have to wait a day or two 'cause the gap between screw and casting threads has been re-established, and gently turn the screw back and forth (quarter turn in, third to half a turn out) to bust up any remaining corrosion or rust as you remove it.
Be careful with an impact driver; they're good on bolts but can provide enough torque to sometimes snap off a screw head.

Steel screws in aluminum housings = electrolysis. As others have said, use pentrating oil, patience, and head. Even then they may be too far gone.

So If they are to far gone and say I snap off every screw can they be saved or should I just snag another pair off of one of the many trailers i see around her that have the original lights but the owners usually just stick on a pair of trailer lights fron the parts store? How much are these lights worth? I dont remember what I gave the guy for them. I orriginaly got them to put on my Jeep rock crawler project that hasnt moved in 3 years and now have this M715 that needs them.

if you bust them off drill them out and retap. Just take your time and do it right. you will be ok. the only other thing I have found in the old lights is that the insides are all tost