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I have the electric door seal pump on my ES and it works very well.  However, on recent flights at higher altitudes (which for my ES is the 9-11,000 range) I have noticed the pump runs a lot more than at lower altitudes.  On one leg of my last trip, at 9,000 feet and about 0 deg C OAT, the pump ran almost continously.  On two occasions I shut it off, let it bleed down, then turned it back on.  It pumped back up, the light went off and I thought everything was fine.  As I watched, though, the light began to periodically flicker, then stay on for intermittent periods then stayed on.  I finally pulled the breaker so the seal would retain its pressure and found that the seal remained inflated for the rest of the flight with no change in cabin noise that would indicate the seal had deflated.

At lower altitude in the later stages of the flight, I reset the breaker and the pump appeared to operate normally ( occasional flicker of the light showing that the pump was keeping the seal at full pressure) just as it has in the past.

I am baffled.  Can altitude (thinner air) have an affect on the pump?  Is this an indication that the pump is wearing out?  Help.  I would appreciate any input.

Thanks in advance.

Jim Scales
98AF

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