[Smith1000]

Just returned from a road trip to Colorado. Lesabre ran great; however, the ac would switch from the vents to defrost on long grades, particularly when accelerating. It had been doing this some during my regular commute, but not all that often. During this trip though, it did it continually. I found if I ran it on bi-level it seemed to hold better and would not switch to defrost as much and if it did when on bi-level, it would return to the vents on its own on the downhill side. I found that if I shut the ac off when cruising when it occurred, it would not always return to the vents (when climbing) when the ac was turned back on.

I also found with the ac on, it got about 21.5 MPG cruising. One morning when cool out, I shut the ac/vent off all together. While crusing that morning, it got about 27.6 MPG.

This morning, I pulled out the controller behind the glovebox and inspected the nipples and tubing. It all looks good and the nipples coming out of the controller are not flexible and soft. I really think that part looks okay. There is a vacuum where the violet vac. tube meets the black tube.

I am tending to think that it is losing sufficient vacuum due to a leak somewhere and that the problem lies somewhere in the main vacuum line that comes into the cab. The leak may be partially responsible for the decreased gas mileage I have been experiencing over about the past 1.5 to 2 years. It has gone from 26 combined to around 21 or less.

I cannot seem to find where the black vacuum line enters the cab (to trace it back). Does anyone know where the vacuum line enters the cab? Is it on the drivers side? My Hanes manual doesn't seem to show any vacuum line diagrams. I followed the line off the engine (near injectors) that connects near where the brake boost vacuum connects. It appears to go directly to the canister under the right front fender. I kind of lose it there. It appears only one vacuum line connects to the canister, but I can't tell for sure what the top of the canister looks like. Is there only one line to the vacuum canister? I do see a line that I believe is vacuum that runs near the bottom of the radiator over under the ECU and loops to the transmission and engine vaccums. Not sure where the one is going that ends up inside for the ac/defrost controls. I am about to go out and take another look. Thanks for any help. I would like to run a new line and connect somewhere in a good spot in the engine compartment.