Product type, e.g.  solar water heater.  
Description of the problem and symptoms (e.g. doesn't heat water, leak, noise, circuit error, won't start). 
Installation date.
Date of the most recent service.  

Photos or videos from the problem area &  photo of the production label (on solar water heaters, it is usually located on the boiler) where the product serial number is written. .  You can attach up to 4 files.  Maximum file size is 3MB.