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Old 01-22-2021, 08:32 PM   #26
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 44,715
 

2003 L-Series 3.0L Sedan
Default Re: another revisitation on old actuator trick

In theory, no one wants to hear the hvac mode, temperature or recirculate doors moving and design sees to that. I can hear the quiet movement of actuators when paying attention to each one but they're not designed to let anyone know they're working. Turning blower speed up, listening for where airflow exits and/or a hand on defrost, face or floor vent are ways to tell if selected mode correlates with air flow. When I thought one of my actuators was acting strange, I used my hand to feel airflow as I went thru each mode to test actuator movement. Member 02 LW300 has tested spare actuators by plugging them into his hvac connectors to ensure each one works (previous replies in this thread). Unless you have a spare actuator for plug n' play, removing one then reconnecting it to its wiring harness and playing with the mode switches may be the only diy troubleshooting method as long as an actuator can be removed to observe the output shaft moving during mode selection. I presume wiring, hvac control head and interior doors of our hvac boxes are intact and in working condition. There's a lot of assumptions on my part and I can be wrong too.

The cabin filter lets you see the recirculate door movement when the filter is removed. I haven't tried to look down the window cowling to see if the temperature and mode door are visible. My guess - the doors are not too complicated for reliability. The actuators doing all the work are, in my opinion, the weak link. Since they easily outlast new car warranty, maybe double the time and/or mileage, they can't be faulted when they fail.
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