I have a small problem with water stain inside on the roof above the window from rain or carwash, maybe left open a crack at some point.
Would anybody have some idea about a good cleaner that won't make it worse?
I checked but could not find any threads about this problem.
Looking forward to hear from any that has dealt with this. Thank you.

 

I found a thread about this problem thanks to Cissy.
Sorry I didn't know it was called a headliner.