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Aspen ACU 910-00004-001

force5

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I think the ACU linking my Aspen to my Century2000 autopilot is faulty. Anyone recently upgraded to a digital autopilot who has a no longer required working ACU?
 

philiplane

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It is more likely that the autopilot has developed a problem. The ACU only feeds course and heading datum to the C2000. You can feed those voltages to the C2000 connector CD175, bypassing the ACU. Any competent radio shop should be able to do this for troubleshooting. The first thing to check is the 4.8 vdc reference signal from CD175 pin 19, going into ACU P3 pins 23 & 25. Without this signal, nothing will come back from the ACU to the C2000.
 

force5

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It is more likely that the autopilot has developed a problem. The ACU only feeds course and heading datum to the C2000. You can feed those voltages to the C2000 connector CD175, bypassing the ACU. Any competent radio shop should be able to do this for troubleshooting. The first thing to check is the 4.8 vdc reference signal from CD175 pin 19, going into ACU P3 pins 23 & 25. Without this signal, nothing will come back from the ACU to the C2000.
Hi Philiplane - You seem to know quite a bit. I tell you why I think its the ACU.
The C2000 passes all its self diagnostics at start up. It will fly in NAV mode, so follow the GPS course with GPSS OFF on the Aspen (I'm not sure it will follow the GPS course in GPSS mode, autopilot in NAV mode - can't remember, certainly won't anticipate turns) and it will intercept and track a VOR. It will not follow the heading bug from the Aspen and will not follow the GPS course in GPSS mode (C2000 in HDG mode). In HDG mode it will stay wings level and if I use the CWS yoke button I can roll the plane onto a new course release the CWS and it will stay wings level

Also the ACU P3 pins 23 and 25 both have 4.8vdc on them.

If you can offer any more insight I would be most grateful. I am stuck in St Maarten in the Caribbean. Fiddling on a hot ramp under the panel. At this point I think if I could swop out the ACU I could at least eliminate that (If I haven't acquired a bum ACU!!)

Edit - and just to add. It was operating flawlessly, then the heading mode became intermittent and now stopped working altogether
 

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