Post a photo so we can see what the problem is.
I've got everything but this one cover off. Here's a pic with the cover I need out circled.

Here's the tool I'm using to remove the screws - it's the only tool I have that fits the screw head.

And here's a close up of the screw that I can't get to.

And here's the damaged brushes because the tool I'm using keeps coming apart and falling behind them.

Thanks hun for all your help! As always, you're incredibly patient with me and I'm deeply grateful. At 58, with a new hip last December and a disabled son at home, I simply have to try and fix these things myself given my $20K cut in pay I took to keep working two years ago.
Let me get this right..... You spent time to clean/clear evaporator coils, ordered and received the defrost heater ( apx. $70 clams ) and defrost terminator ( apx. $ 12 clams) .....but you only install the heater and are going the see what happens ?????? You have it apart once, fix it once........... If you never tested the defrost terminator to see if it had failed, you might as well just replace both items, reinstall the cover, and have a beer.................................................If you call a 'repairman' and he sees that you started to work on it, it'll cost you a few shekels....He will not know if it is miss-wired, missing parts, was not the original complaint.............I charge extra if a customer starts a repair and then bails out on the repair..................