'90 300 SEL sunroof does not work
 

What could cause it to not work? The electrical part works, I hear a humming, but it does not go back. A mechanic with a quick look thinks it will be $1400 to replace. True?

Could be a disconnected/broken cable or connection. Also a possible stripped gear in the motor. Sunroof repair is very costly, I was quoted $2000 from the dealer. The cost is mostly labor and a lot of mechanics will not touch it.

There is a great amount of posts on this subject with much detailed info. I repaired mine for just the cost of a new cable. It takes time and patience but I had mine like new in one day. I work very slow and take the time to clean/check everything while the opportunity presents itself.

wow - amazing. and it looks so simple.

It is rather simple, most of the time was consumed by removing the trunk panels and the removal of the sunroof motor. I was very careful with removing the sunroof headliner. My goal was to avoid further damage and understand the workings of the sunroof. Since the cable was stuck in the guide tube it took me a while to free up the sunroof. It required removal of the sunroof motor which entailed many climbs in/out of the trunk and various body positions.