I've seen all the post refering to tsb #242499, which is the problem I have, I purchased the check valve from the stealership but they will not tell me how to install it (they are crooks). If anyone has this info and can let me know I would appreciate it. I have the basic info, put into the vacuum line going to the heater. Yup, but I could use a little bit more direction, lol. This is a 1999 Grand Cherokee Larado, 4.0. Thanks for your help. Bill