Welcome to Justanswer, My name isXXXXX am here to help.
I believe there is either a vacuum leak or the check valve is bad on the control unit for the climate control
CLICK HERE FOR THE TEST PROCEDURES
This is what will need to be tested. If you dont have the tools the shop will probably charge 1 hour of labor to complete this and find the vacuum leak if the check valve is bad this will be about 10 bucks.
Let me know if you have any questions. If this was helpful please take a moment to kindly press the green ACCEPT button in the lower right hand corner. Thanks in advance Danny
I knew that I had a vacuum. I need to know where the check valve is and how to check for leaks