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Pete, Technician
Category: Mercury
Satisfied Customers: 29138
Experience:  Over 17 years diagnosing and repairing automobiles various makes and models with some training and certifications.
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Second opinion], I'm not sure that there an answer to my

Customer Question

Second opinion] Hello John, I'm not sure that there an answer to my question, other than change the actuator. [Darn, by the time I had finished writing this I think I figured it out.]2008 MGM. Blend door actuator malfunctioning. I watched a video made by tech about why they fail. The type I likely have is the square box looking actuator. This design had good very good position sensors but small gears that broke easily.After disconnecting/ reconnecting ground and then starting the car, and then calling for A/C, I can see the blend door actuator moving the arm. Cold air is being delivered. Within moments the blend door actuator moves back to heat position. This happens every time.So, obviously the gears aren't broken. And, obviously, each time I call for A/C on system 'repower-up?' the blend door moves to the A/C position before moving back to the heat position. So, when the actuator gets to the A/C position it must send a signal somewhere that it's where it's meant to be.So, it sends the signal [or not] and a three Mississippi count later the actuator moves the blend door to the heat position.
Submitted: 5 months ago.
Category: Mercury
Expert:  Pete replied 5 months ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

The actuator has a position sensor in it.This sensor can act up causing the control unit to move the actuator back to where it was or in the heat position.I have seen this before in the past and had to replace the actuator.The other cause is the heater/ac control unit on the dash can send a false signal turning it back to heat but in most cases it is the actuator itself with the position sensor failing internally with the actuator needing replaced.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete