apu 'no rotation'

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apu 'no rotation'

Postby hendaz04 » 17 Jun 2009, 10:41

I have been troubleshooting a fault with 737Ng apu fault code 49-41012 apu no ration. This however only occurs during 2nd apu start. Apu starts fine 1st time everytime, just never the 2nd time. starter gen, apu inlet door sensors, spu,scu changed as pair, ecu and wiring harness of starter gen all been swapped or replaced. Wiring checks c/out as seems fine. anyone with experience of this please feel free to offer advice, a bit of a head scratcher
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Re: apu 'no rotation'

Postby sjap » 17 Jun 2009, 16:23

Maybe its aft bearing / axle is deteriorating inside.
The first time its cold, and when its rotating, it will continue running to 100% .
But the second time all is hot. The axle / turbine is getting stuck and theres no rotation anymore.
I think you need a new APU. We had it last time, the same on a NG, the aft bearing had play and was causing the turbine to hit the outer casing.
Rgds
sjap
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Re: apu 'no rotation'

Postby hendaz04 » 18 Jun 2009, 04:46

Further invest this evening: apu ran for approx 10 mins then shutdown. manual rotation c/out immediately once at 0% rpm. Apu rotates smooth and free :idea: time to put in some leave!
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Re: apu 'no rotation'

Postby Jose » 03 Mar 2015, 16:39

A Boeing 737 800 has an APU, P/N: 3800702-1 with no roration during start and APU FAULT LIGHT on P5 fwd overhead panel. After ECU BITE we found these msg: 49-41248 & 49-41254. Starter converter unit and Starter-generator have been replaced, once at time and still the problem is there. Some times the APU starts for 2 times and fails to start at third attempt. Please provide any help.

We check the AfT turbine rotation and we found ok after APU fail TO start again.
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