Drivers Door Won't Stay Open

My drivers door won't stay open like it used to. It had like a detent in the swing when almost open. The right one is fine...is this an adjustment or do I need to replace something?
Thanks,
Sonny

I've had other cars that this happened on, but I have no idea about your trouble. Keep us posted!

There's usually a spring loaded detent in the door hinge area. Check out the passenger side door to see how it works and then see what's not working on the drivers side.

I have looked to see if I can find something out of place or different from the other door but I can't find anything.
Sonny

I have located the problem...it's the metal bar that goes in and out of the door and is about half way between the two hinges. The right side is tight and the door works fine...the left side flops around and feels like it's not attached to anything...are these hard to change?

I found out today that the part I need is called a door check and there is one part number for both sides and cost 35$ at the dealer.

how hard are these to replace? i would like to know in case mine ever break

I wondered how hard these are to replace as well cause I think mine are done. I'm always fighting the door on the simplest of inclines.

I bought a used right side door check and put it on the left side and it works great. It's really simple to remove the door panel and it only has three bolts but I did run into a snag. I was having trouble with it before but I can't leave the door lock/unlock selector on the door. When I hit the unlock button or use the unlock button on the fob the metal arm can't move the slider over far enough to unlock the door. If I leave the selector off it works fine. What could be wrong? The selector move easy and looks fine to me.