Join Date: Jun 2006
Location: Eastern ON Canada
Car: 07 OBW 2.5i D-4AT
Feedback Score: 5 reviews
That is strange. I can't think of how it could be a fault in the mode switch(es) if the same switch is being used in both cases, and the ignition switch is also at the same On position.
Is there any change in any other climate control function, for example, does the blower fan work fine in both cases? And does the recirculation function work in both cases? (The latter might be harder to determine, but with the blower running there's usually a distinct change in the air flow sound when the recirculate position is selected or turned off.)
Also, I believe the 99 has the push-button selectors for mode (floor, defrost etc) and each shows a small light when it is selected. (If I'm wrong please let me know.) If so, then when a different mode button is pressed, does the light in that button come on and the one in the previous selection go out?
One thing that does change when the engine is running is that the alternator is turning. Normally, the battery voltage will be higher with the engine running -- battery voltage will be around 12.7 V or less with the engine off, but up around 14 - 14.5 V with the engine at 1000 rpm or more. How this can affect the mode actuator is a puzzle, but it's about all that changes. Might be an idea to verify that the battery voltage is in these ranges with the engine off and running.