Air not flowing correctly
#1
Air not flowing correctly
Im having a problem with my a/c only blowing through the bottom vents i have replaced all actuators just for good measure and is still blowing only at the bottom vents, does anyone know what could be causing this if it could possibly be the hvac control module?
#2
Registered Member
iTrader: (3)
What happens you press the DEF button? The FRESH/RECIRC button? Does the temperature blend door move when you rotate the temperature dial from 60° to 90° and back? Or, no matter what, none of the blend doors do not move at all?
If you haven't already, you can download section HAC (Heater & Air Con Control System) of the factory manual from here. There is a thorough, in-depth self-diagnostic function built into the amp that you can access to determine if the amp is the issue. I would say that 99% of the time it is the amp.
If you have a multimeter, check to make sure each LCU (blend motor) connector is receiving power and ground. Assuming good power and ground, then the amp is likely not sending the COM signal.
If you haven't already, you can download section HAC (Heater & Air Con Control System) of the factory manual from here. There is a thorough, in-depth self-diagnostic function built into the amp that you can access to determine if the amp is the issue. I would say that 99% of the time it is the amp.
If you have a multimeter, check to make sure each LCU (blend motor) connector is receiving power and ground. Assuming good power and ground, then the amp is likely not sending the COM signal.
#4
Registered Member
iTrader: (3)
If memory serves, the air mix actuator is on the driver-side, while the mode and fresh air actuators are on the passenger-side. With the key ON (engine OFF) you should be able to hear the actuators moving- if they are working. If nothing, then diagnose power and ground.
My guess is the amp but properly diagnose the issue before throwing parts at it like you did with the actuator motors.
My guess is the amp but properly diagnose the issue before throwing parts at it like you did with the actuator motors.
Last edited by ILM-NC G37S; 05-15-2023 at 06:47 PM.
#6
Registered Member
iTrader: (3)
By "amp" I refer to the "Unified Meter & AC Amplifier." This is a small, white, plastic rectangular box that is mounted to the AV headunit. This module is responsible for all gauge, HVAC, and other select functions.
In this case, the amp is responsible for providing power and ground to each individual blend door. The amp also sends a command signal to each blend doors' LCA which tells the door to open/ close and by how much via a local COM signal wire. You can easily check if the motors are getting good power and ground using a multimeter. If good and they are still not moving, then the local COM signal is the issue.
Again, the FSM link I gave you above has all the steps you can take to use the self-diagnostic function and determine what the issue may be.
***FRIENDLY WARNING*** Please be sure to mark each connector as you unplug them to ensure they get placed back in their correct slot. It is VERY easy to mix up connectors in that center stack. A misplaced connector can/ will brick your car.
In this case, the amp is responsible for providing power and ground to each individual blend door. The amp also sends a command signal to each blend doors' LCA which tells the door to open/ close and by how much via a local COM signal wire. You can easily check if the motors are getting good power and ground using a multimeter. If good and they are still not moving, then the local COM signal is the issue.
Again, the FSM link I gave you above has all the steps you can take to use the self-diagnostic function and determine what the issue may be.
***FRIENDLY WARNING*** Please be sure to mark each connector as you unplug them to ensure they get placed back in their correct slot. It is VERY easy to mix up connectors in that center stack. A misplaced connector can/ will brick your car.
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#9
Registered Member
iTrader: (3)
Do not fall into the trap of throwing parts at a problem without proper diagnosis. Doing so will cost you a ton of headaches and money and still might not resolve the issue. Your problem could be the amp or it could be a broken/ pinched wire, a bad ground connection, bad switch panel, etc.
All of the information for diagnosis and repair relevant to your issue I have provided above. If you have a multimeter and are skilled in using it, then you should be able to follow the wiring diagram in the FSM and test each relevant circuit for voltage and/ or contnuity.
I do not know your skill set so please take no offence, but if you do not feel comfortable or are not able/ willing to do the work, then perhaps you should find a reputable mechanic to look into the matter.
All of the information for diagnosis and repair relevant to your issue I have provided above. If you have a multimeter and are skilled in using it, then you should be able to follow the wiring diagram in the FSM and test each relevant circuit for voltage and/ or contnuity.
I do not know your skill set so please take no offence, but if you do not feel comfortable or are not able/ willing to do the work, then perhaps you should find a reputable mechanic to look into the matter.
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