Eng123,
I had a Dual Bleed light illuminate during taxi with the APU Bleed Air switch in the OFF position. I elected to shutdown the APU and the problem went away. So, in my case whether the APU was running or not was indeed important. I believe the catch here is not the engine bleed switches but rather the position of the APU Bleed Air Value. Are there any pprunes out there that could shed some light on the exact location of the APU bleed valve sensor? Is it on the value itself , located downstream of the duct, or on the one way flapper check valve??
I guess closely examining a rise/drop in APU EGT indication would be the only way in which one could determine bleed air valve status?? However, placing the APU off was a quick and effective solution at the time. I was just wondering why Boeing elected to leave this step out ???
Thanks