Unfortunately I do read quite a bit about heater / ac controllers causing problems. You're right about two actuators going bad at the same time. There is only one heater core but two temperature mixing doors. Most newer cars, (a '98 model is new to me), use electric motorized actuators instead of the previous vacuum motors or the even older, (and much more reliable) levers and cables. Still, the temperature doors normally move so slowly you may not hear them. The best way to tell if they're moving is to look for a linkage that moves in response to adjusting the controls. Some actuators don't use linkages so there's nothing to watch. Those actuators can often be unbolted and pulled out, then you can watch the shaft.
If your car does have vacuum motors, pull a hose off one and feel for the presence of vacuum while the engine is running and you adjust the controls. Temperature doors don't typically use vacuum motors because they are difficult to stop in specific positions. Vacuum motors are normally used for mode doors that are fully opened or closed.
With an actuator removed, you might be able to turn a temperature door by hand. Sorry I can't be more help on your specific model. I've rebuilt a few crash-damaged dual zone heater boxes, but those were all on 2006 and 2007 Dodge trucks. How about you buy a Dodge truck, then holler back when the heater on THAT one fails?
Friday, September 10th, 2010 AT 5:25 AM