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Gunvir Singh
Gunvir Singh,
Category: Chevy
Satisfied Customers: 1646
Experience:  Master Tech at Kennesaw Auto Tech
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2007 chevy trailblazer ss, steady loud knock behind glove

Customer Question

2007 chevy trailblazer ss
JA: Are you fixing your Trailblazer yourself? What have you tried so far?
Customer: steady loud knock behind glove box when turn motor on. AC/heat works, but think may be blend door actuator'
JA: Have you checked the coolant level? Has there been any leaking from the hoses?
Customer: no
JA: Anything else you want the mechanic to know before I connect you?
Customer: I love my car?? lol but the knock is relentless
Submitted: 1 month ago.
Category: Chevy
Expert:  Gunvir Singh replied 1 month ago.

Hello, let me rebiew your request. Please stand by.

Customer: replied 1 month ago.
okay thank you!
Customer: replied 1 month ago.
car not here for phone call remedy
Customer: replied 1 month ago.
turn on vehicle, loud knock starts and continues until shut off. heat ac works fine.
Expert:  Gunvir Singh replied 1 month ago.

No need to call, just ignore the pop up.

Expert:  Gunvir Singh replied 1 month ago.

Are all the ac air controls working fine?

Customer: replied 1 month ago.
but past couple years onlybon high setting for ac...doesnt blow on 1,2,3 or 4
Just 5 on knob for Ac or heat flow
Expert:  Gunvir Singh replied 1 month ago.

The noise from behind the glove box is from eithe the defrost/ passenger air temp ot mode door actuator. They are installed close to each other. The issue with the blower only working at high speed points towards a faulty blower motor resistor.

Customer: replied 1 month ago.
How determine which it is
Customer: replied 1 month ago.
I had reliable mechamic say had take dash apart get at it but forgot what said problem was
Expert:  Gunvir Singh replied 1 month ago.

The complete dash does not have to come apart. The instrument panel carrier will need to be removed to get access to the HVAC housin where these actuators are installed. At that time you can touch the actuator and check which one is knocking.

Expert:  Gunvir Singh replied 1 month ago.

Only other way is by using a compatible scan tool to command the actuators one by one and check which one is the culprit.

Customer: replied 1 month ago.
both repairs do not require pulling dash
Expert:  Gunvir Singh replied 1 month ago.

Let me confirm. Do you have electronically adjustable brake pedal?

Customer: replied 1 month ago.
Not sure
2007 chevy tb ss
Expert:  Gunvir Singh replied 1 month ago.

Do you have the VIN number. I can check it with that.

Customer: replied 1 month ago.
Not rigjt now car willbe back 530 pm
Expert:  Gunvir Singh replied 1 month ago.

No problem. Let me check, if i can get the info without the vin.

Expert:  Gunvir Singh replied 1 month ago.

You do have automatic temperature control?

Customer: replied 1 month ago.
No auto temp contril
Manual w knobs
Expert:  Gunvir Singh replied 1 month ago.

Ok. Unfortunatelu on that model dash will need to be removed. It calls for approx 5 hours of labor.

Expert:  Gunvir Singh replied 1 month ago.

Do you have any other questions?

Customer: replied 1 month ago.
wha t part needs be replaced please
Customer: replied 1 month ago.
What part?
Expert:  Gunvir Singh replied 1 month ago.

For the noise one of the door actuators. Need to get access to the HVAC housing by removing dash to determine which one is faulty. In my experience i will recommend to replace all three as all three have same age on them. The actuators are not very expensive the labor is. If you only change one and another one goes out then you will be paying for the same labor again.

Expert:  Gunvir Singh replied 1 month ago.

And for the blower speed issue, i will recommend to check the blower motor resistor.

Expert:  Gunvir Singh replied 1 month ago.

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Expert:  Gunvir Singh replied 1 month ago.

Hello, just checking if any updates?