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John Brems

John Brems

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Just had complete fuel setup on my Ovation2 M20R with Continental IO-550 G engine. This required numerous full throttle runs with upper cowling removed so fuel flow adjustments could be made.  Now the “alternate air” indicator light flickers ON  and OFF on the cockpit panel during takeoff and under high power situations as if the switch is vibrating in a way to close the light circuit.  Once power is reduced the light goes off and stays off.  I have pulled the manual cockpit lever several times and when pulled to “alternate air ON” the indicator light comes on as it issupposed to.  Does anyone where the activating switch is under the cowling so it can be inspected?

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My M20R with the 310 hp conversion does the same thing and I have a K&N air filter. I think it’s sucking in so much air that it opens up the alternate air door. The alternate air box is located on the pilot’s side in front of the fire wall.

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Welcome aboard John.
 

+1 for inspecting the Alt air door.  It is magnetically held closed tight... it may help to have assistance to find it... somebody to operate the lever...

Best regards,

 -a-

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John, I was having a similar problem.  On departure the alternate air would open or the light would flicker.

the problem was the air filter.  At my most recent annual 4 months ago I was told the air filter was just packed with dirt, dust, bugs.  I told the shop to replace it, but they said actually cleaning the air filter is the appropriate course of action.  So, once cleaned, the alternate air indicator hasn’t come on again.  

Check your air filter.

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John,

If you would like...

You can edit the title of your thread...  :)

As the OP, you have the right... there is a button for that...

You might consider something more direct to your issue...

Best regards,

-a-

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On 7/26/2020 at 9:58 AM, buddy said:

My M20R with the 310 hp conversion does the same thing and I have a K&N air filter. I think it’s sucking in so much air that it opens up the alternate air door. The alternate air box is located on the pilot’s side in front of the fire wall.

Correct.

@John Brems, make sure the magnet is properly securing the door closed, and that the cockpit handle is moving the cable to full forward and aft travel; such as to secure the door and magnet.  About 9 years ago, before I found Brian Kendrick, I had one shop replace a broken magnet (simply due to age) by using a common kitchen cabinet magnet and not the proper Mooney part.  Make sure you get the proper part number in the event you need to replace the magnet.  I've seen more than one give out under wear/age.

Steve

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When I bought my Ovation II last year (310hp), the alternate air door popped open at full power too. It closed as soon as power was reduced after takeoff. The A&P/IA who looked after it mentioned that a basic kitchen cabinet magnet was in the parts book but, after I had the plane for a few months and the Mooney factory started shipping parts again, we ordered a magnet directly from the factory which was a much more robust part than the kitchen cabinet magnet on there before. Not cheap but the Mooney magnet is worth it in my view. Once in a while, it still pops open at full power but more often than not it stays closed.

If you have the top cowling off, you'll see where the alternate air door is (upper rear left part of the engine bay) and you can push the door open with your hand and then see it spring back and catch on the magnet. It was good to see it in this location as I think it minimises the chance of FOD getting into the engine when the filter is bypassed.

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Yeah, the popping open of the door at higher power can generally be resolved by checking the cable rigging that pulls and pushes the door, as well as making sure the magnet is seated/mounted properly and squarely so it secures solid when closed.  After adjusting mine a bit after replacing the kitchen magnet with the correct one, I've never had it pop open since.

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There's something to be said for neodymium magnets. All shapes, all sizes, all strengths. I buy them from amazon to make fixtures at work . . . . and at home . . . . Strong little buggers! You just about can't pull a 1/2" cube neodymium magnet off of a block of steel, but it can be slid / nudged off of a piece of sheet metal. 

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