How can I fix my Rug Doctor (wide track)?

I let a neighbor borrow our rug doctor and when I got it back it overheated shortly and I was only able to use it again a short time after I let it cool down. I discussed it with her and found out she was going by the level in the container and not the top clear tube to determine if the water was gone and had it overheat with her as well. What can I do to fix it?

Susan Phillips
September 2012