What should I use to clean the headliner? There's some small mold/mildew spots. Overall, the original headliner is in fair condition so I don't want to replace it yet.
Rent a commercial level carpet cleaner with the upholstery attachment on the separate hose with the brush. Start with a mild soap solution for fabrics. Spend extra time with the vacuum setting to pull as much moisture from the headliner fabric as you can.
Alternatively I've used a soft bristle brush with pail of soap solution and then used wet/dry shop vac to remove the excess solution. Messy, but it can be effective.
that's the stuff that people use to clean the soft roofs on convertibles, rag tops get all mildewed and stained and the stuff takes all that off and kills the green moss stuff that grows. its suppose to kill everything and then protect the Vinyl.
i bombed my headliner once with the stuff and it has been clean ever since. i used a micromesh cloth to wipe it down and the cloth basically turned black from the garbage that came off.
i don't know about the new stuff called raggtopp i got mine from a website like 10 years ago.
I just used Simple green/water mix and a soft sponge. I worked great but mine is black so it doesn't show as much as lighter color materials, still I'd try it.
Many methods to try. I only caution you on using a mild cleaner. My original headliner was in good shape but after cleaning with some Bleche Wite the threads started deteriorating soon after and unraveling. Live and learn.