By on December 29, 2017


2009 Nissan XterraMike writes:

Ok Sajeev, I got one for you.

I own a 2009 Nissan Xterra 4wd X model.  It has nearly 100k miles on the clock.  In the past week, whenever I start the vehicle, I hear a chattering noise coming from the passenger side dashboard.  The noise persists as long as the passenger air bag light is lit; when that light goes off, the chattering stops.  So I took the truck to my local Nissan dealer, whom I trust, and I was told that the problem is the passenger side blender door of the HVAC system – apparently there are gears in this assembly which are not moving freely or properly. 

The cost to repair is estimated at about $600 because of the necessity to remove the whole dashboard.  The dealer’s service people told me to do nothing until the HVAC system fails to function properly, and it is currently functioning properly except for the above described noise.  My question: how is a bad blender door mechanism linked to an airbag light?  Can airbags chatter on vehicle startup?

Thank you as always for your excellent advice.

Sajeev answers:

First try resetting the air bag light. If that doesn’t work, let’s trust your trusted dealer on the blend door actuator, and allow me to meander as I cannot Google a precise explanation.

I have a similar problem with my (now fully restored) Lincoln Mark VIII after suffering a front-ish fender impact (i.e. airbags didn’t pop). Now the air bag light/buzzer triggers if the headlamps are on during start up. I disabled the automatic headlights and delayed my knob twisting, keeping the Air Bag Diagnostic Monitor happy.

Which makes me happy, and I’ve invested in a set of factory shop manuals. (You should too!) So let’s see how two seemingly unrelated items are linked:

1995 Lincoln Mark VIII Fuse Box Wiring, Image: Sajeev Mehta

After starting the Mark VIII, fuse #10 juices up several things, including that Air Bag Diagnostic Monitor (second box from the left on the bottom). So when I crank on the headlights “too early” after startup, the circuit (in the multifunction switch?) drops the amount of juice (voltage?) which upsets the Air Bag Diagnostic Monitor’s 22 year-old circuits. My logic is pathetic, but the result is clear.

What’s the point? Air Bag health indicator modules are, as they age, hyper sensitive to external influences.

If anything looks wrong, the system is engineered to assume the worst and get the owner into a repair shop. This ensures fewer manufacturer lawsuits the air bag system will never be neglected and always save lives.  

Just buy the shop manuals with wiring diagrams, please!

[Image: Nissan, Sajeev Mehta]

Send your queries to [email protected] Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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19 Comments on “Piston Slap: Xterra’s External Air Bag Influencers?...”

  • avatar
    Jeremiah Mckenna

    I have the same problem in a ’98 Chevy 1500. Not with the airbag light, but with the blender door mechanism. It clicks a lot when I change the temp. However, I have climbed under the dash and looked at the area where the noise is coming from. Unfortunately it is not on the open, and I must remove and or dismantle a lot of stuff in order to replace a $5.00 part. It is annoying, but eventually stops, but along with all of the other rattles in the cab this is one of the least annoying by comparison. So, when it warms up outside I’ll become a contortionist and repair/replace the parts.

    Being in the car business I have hears this “clicking” happen a lot in older cars that are traded in, regardless of the year/make/model. Depending on the year/make/model, sometimes this repair can be too expensive and the car will go directly to the wholesale lot because too many people hear that noise and are instantly turned off of that car. The funny thing is, I have bought a few of these cars, repaired the tiny part and made a large profit a few weeks later.

    • 0 avatar

      You should be able to find step by step instructions on how to reach this from underneath the dash in your GMT400.

    • 0 avatar

      My cousin’s 1995 K1500 does this also. If it were mine, I’d probably fix it because sometimes it doesn’t change when the selector is moved, but he isn’t worried about it, and the truck has other issues which would be more important if any sort of reconditioning were to be attempted. As it is, its just a beater camp/fishing truck, nothing more, and it serves its purpose.

  • avatar

    I was told that the clicking blending door actuator was a recall item on my ’97 Town Car. A good Lincoln mechanic can install a new one by partly removing the AM/FM cassette radio. Yes, yes, obsolete today, I know it.

  • avatar

    The ’08-’12 Ford Escape has 3 or 4 of these actuators, depending on the model. They are notorious for going bad and make a variety of cricket, clicking and ratcheting noises as they age.

    Two of them are dead simple to get at. One can require removal of the dashboard. But some very smart person came up with the idea of removing the glove compartment and using something like a dremel to cut a hole in a plastic box in the hvac system. You replace the offending blend door actuator and fibreglass the panel back into place.

    It would be worth checking part placement to see if this can be done on the Xterra.

  • avatar

    Same thing happened with my 03 Tahoe. I got a few clicking noises when I’d change temp, and eventually the driver’s side would sporadically go hot when the AC was on, and passenger side cold. Diagnosing the issue, the blend door on the *passenger* side controls the driver’s vent temps.

    A $35 part and an online instruction manual (and an hour of labor) later, and now it’s all fine. Required the removal of a panel under the dash, and some hard to access screw removal for the actuator. From what I read, dealers charge several hundred dollars to fix this.

    I’d see if you can get to the blend door actuator from a different locale, via some forum searching. Eventually it’s going to go bad, and you wont’ be able to adjust your temp for half/all of the front of the car.

  • avatar

    My 2000 Audi was pretty much built around the HVAC box, and a lot of older cars got sold or scrapped due to the labor to r&r the entire dash. Thank God for the hackers figuring creative ways around designed-in stupidity, and sharing the knowledge.

  • avatar

    Can the OP clarify something? When you say the “Passenger airbag light” you mean the light that indicates whether someone is sitting in the seat and thus the airbag is enabled, right? Not the airbag fault light? So it only makes the chattering sound if someone is sitting in the seat? Or does this light come on for a while then go off regardless? I think Sajeev is on the right track – there is some power or ground connection being shared.

    I had to do the actuators in my P38 Range Rover. One of those jobs where there is the factory way to do it or the easy way. The factory way beloved of dealers is to take the entire dash apart, 10hrs+ labor. The easy way is by cutting the air duct that runs in front of the actuators that can’t be removed without taking the dash out. Then put it back together with – wait for it – DUCT TAPE! And I bet the less scrupulous dealers use this method and still charge book time for the job… Oddly enough, the actuators are shared with the Peugeot 405, and are cheaper bought from Peugeot sources, as they will sell you just one instead of all three wired together.

    • 0 avatar

      Now that’s an awesome story.

    • 0 avatar

      You might want to specify real metallic duct tape. Not the grey stuff that will dry out from the heat.

    • 0 avatar

      As soon as I read the first sentence in the article, my first thought was: Peugeot 405 :-)
      Needless to say, I got the same issue on my 405, so i removed the actuator, put it apart and studied a bit, maybe it may be of interest for TTAC readers as well.
      Actuator is very simple, having one small motor, gearbox with plastic gears, a “flap” and a small circuit board. There are 3 wires going in (if I remember correctly) and that’s all.
      Generally for such devices, there should be some kind of sensor signalling when the flap is fully open or closed, but there is none present in this device.
      So, how does it work? (this particular module is for selecting outside or recirculated air, so it has only 2 positions – fully open or fully closed)
      2 wires are for 12 V power supply, and the 3’rd one set the position – 0V means one side, 12V the other. When you change the setting, it will start the motor in the appropriate direction (depending on the voltage) until it reach the end position, which is recognized by the increased load on the motor (that is the purpose of the circuit board) and then it stops the motor. The same thing happens when you start the car (the module have no idea of the position of the flap, so it will try to set the position again, until it recognize increased load and stop the motor, even if it is already in the desired position). So after few years, plastic gears will give up and start grinding and skipping teeth, and there will be no sufficient load to be recognized to stop the motor – and there you have it.

  • avatar

    We had a pathfinder of the same vintage that had this happen. This is very easy to change from the passenger foot well. Takes about 20 minutes and a screwdriver. Part is about $80 from Nissan. Check for a technical service bulletin on it. Our Pathfinder had one adding a new $1.37 plastic washer to the installation to keep it from failing again. Never had the problem again.

    • 0 avatar

      I would check the forums to see what others say about Xterra blend door motor replacements. There are too many shops charging $500+ for simple one hour tasks. What the customer doesn’t know…

  • avatar

    I think it’s just a coincidence/timing thing that the light and the blend door/hvac flap noises happen at the same time. It sounds like the systems are in a “self test” mode. The srs is testing its system integrity and seeing if a passenger is in the seat or not and the hvac is trying to move that failed component to its commanded position.

    • 0 avatar

      It’s not a coincidence. The car is running all of it’s self tests at the same time- airbags, HVAC, ECM, etc. You don’t notice 95% of the items being tested. In this instance, the motor is being triggered to run through it’s motions to check for binding and since the motor is failing you hear it click. At the same time the restraint system is testing connections and processes. Neither failure caused the other, but it’s not coincidence they manifest at the same time.

  • avatar

    My 2009 Altima did the exact same thing once its age advanced. I did not bring it for repairs as work cars tend to be decommissioned once they get up there in mileage and I was kind of attached to it…happens when you have spent a total of 7 months worth of time in a car for a bunch of years.

    No harm ever came of the noise as the blend doors continued to work. BTW, I believe the passenger air bag light has nothing at all to do with this problem. It times out over a fixed period of time and that time seems to mesh with the time it takes for the noisy blend door to move into position on start up.

  • avatar

    Since sensors and switches go bad, automakers should make an effort to make them easy to replace. I smell a class-action suit, and/or government regulation! Oh, wait! These are out-of-warranty cars, and regulations are being slashed as we comment. We’ll have to depend on the hackers for quick fixes, and follow shop manual instructions for extensive disassembly of, er, assemblies.

  • avatar

    I don’t care where I read it – seeing Mark VIII in print anywhere warms my heart. I just spent three of the holidays stripping every usable part from a low mileage ’97 base. When one of these with an operable blend door, a tight steering column and charged airbags comes to a PickNPull I should just move to the closest motel. I’m wondering if your car is fully restored one weekend at a time or all done at once? Doesn’t matter. The two door V8 rear drive cruiser is fast achieving unicorn status. Or fellow sufferer. I cannot decide.

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