Maxxair Fan – Lid Opening Mechanism Problem

[orbsah]

We discovered the mechanism that drives the vent lid open/closed failed. What actually broke is the plastic mounting feature on the vent frame (viewable from the roof) that secures the operator mechanism (the die cast gear box that drives the lift arm up/down). I was able to repair the operator mount with a short piece of aluminum angle. However, I found the motor inside of the unit seems to run way too long. For example, when I have the lift arms in the closed position, my wife hits the OPEN button and the arms raise properly, but when the arms get to their full open position (about 45-deg up), the motor keeps running for way too long then jams everything up. Once it’s all jammed up, the lid mechanism is now stuck (can’t go up or down). I’m wondering if that’s what caused the plastic vent frame to fail in the first place.

So what actually controls the motor ON time? I see there are no sensors to indicate position feedback. Is it just a timer in the electronics? Is there a current sensor that knows when the mechanism hits the hard stop? Any insight would be appreciated.

 

[trailrydr]

We discovered the mechanism that drives the vent lid open/closed failed. What actually broke is the plastic mounting feature on the vent frame (viewable from the roof) that secures the operator mechanism (the die cast gear box that drives the lift arm up/down). I was able to repair the operator mount with a short piece of aluminum angle. However, I found the motor inside of the unit seems to run way too long. For example, when I have the lift arms in the closed position, my wife hits the OPEN button and the arms raise properly, but when the arms get to their full open position (about 45-deg up), the motor keeps running for way too long then jams everything up. Once it’s all jammed up, the lid mechanism is now stuck (can’t go up or down). I’m wondering if that’s what caused the plastic vent frame to fail in the first place.

So what actually controls the motor ON time? I see there are no sensors to indicate position feedback. Is it just a timer in the electronics? Is there a current sensor that knows when the mechanism hits the hard stop? Any insight would be appreciated.

That motor is stoped by friction from the arm not being able to extend any more. One of the great designs that actually causes the potmetal body to break in the first place over time from stress. It could happen basically anytime... and does. We replaced ours after 5 years of service, others sooner than that.

As for your situation, would ensure you replaced all parts in the mech and aligned the door, crank motor and lift arm properly. Mine came with new crank motor and shaft.

 

[orbsah]

Got it! Turns out I didn’t have the lift arms seated properly. All good now - thanks!

 

[18CrewDually]

As far as I know the motor has a built in Thermistor that when the motor is stopped (stressed) it over heats the thermistor which then cuts power. That's why there's a little delay until the motor stops.
Also, if you add vent cover toppers you'll notice it will hit that before stopping. It's no issue and is expected to act as usual.
I'm surprised the bracket broke. On mine the cast body of the gear box grenaded. I was able to source another one from my dealer.

 

[orbsah]

Right, now I understand there’s circuitry that detects when the motor stalls open or closed. Much cheaper design as compared to using limit switches or equivalent. Oh well.

I’ve seen several reports where the cast metal gearbox failed. Other than mine, I haven’t found any other reports of the plastic mount breaking which is what sparked this curiosity in the first place.

Thanks!

 

[trailrydr]

As far as I know the motor has a built in Thermistor that when the motor is stopped (stressed) it over heats the thermistor which then cuts power. That's why there's a little delay until the motor stops.
Also, if you add vent cover toppers you'll notice it will hit that before stopping. It's no issue and is expected to act as usual.
I'm surprised the bracket broke. On mine the cast body of the gear box grenaded. I was able to source another one from my dealer.

Unless under $20.... Amazon is 2 day in most areas at $16 plus tax.

https://www.amazon.com/10A20281K1-Replacement-Operator-Mechanism-10A20281K-1AF/dp/B0DFWXLGWJ/ref=asc_df_B0DFWXLGWJ?mcid=3777c83b511839958a439777d7065f7c&hvocijid=12422702180835604619-B0DFWXLGWJ-&hvexpln=73&tag=hyprod-20&linkCode=df0&hvadid=721245378154&hvpos=&hvnetw=g&hvrand=12422702180835604619&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=1026339&hvtargid=pla-2281435178138&psc=1

 

[18CrewDually]

Unless under $20.... Amazon is 2 day in most areas at $16 plus tax.

https://www.amazon.com/10A20281K1-Replacement-Operator-Mechanism-10A20281K-1AF/dp/B0DFWXLGWJ/ref=asc_df_B0DFWXLGWJ?mcid=3777c83b511839958a439777d7065f7c&hvocijid=12422702180835604619-B0DFWXLGWJ-&hvexpln=73&tag=hyprod-20&linkCode=df0&hvadid=721245378154&hvpos=&hvnetw=g&hvrand=12422702180835604619&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=1026339&hvtargid=pla-2281435178138&psc=1

That was my 2nd option. My dealer supplied it for FREE and immediate so no waiting.