Ray, the covers are plastic, and of course these coils work. That's what they're made for
If your friend cannot remove plastic covers he should really seek professional help.
Did you watch the YouTube video? This kid did not solve his problem but he did find water in his coils. At least he is willing to try. His next step should be to ring out the coils with a meter to find any bad ones. Believe me, bad ones always show up. - Dave