I’m not sure on your 91, but the newer ‘00 < there is a valve that red and blue lines tie into. It has multiple functions, but it sounds like it’s hung up or broke. It comes spare pretty simple but the parts have to go back together in the order and direction. If your handy take it apart and see if there’s anything stuck or O-rings cut. Might not hurt if you call around and find a price and availability before you tear into it. (May not need it, but you’ll need to know where to go if you do.)