C208B G1000 acu troubles

[airwrench]

Hi all

Been having some difficulties with the ACU's on one of our caravans, seems to like going through ACU's and cannot find a reason. First was on delivery, then about 2 months later, next 2 lasted only a day, next one a week, next one 2 weeks. Been through wiring, changed alternators, changed GCU's. Anyone else have this problem, any suggestions. The aircraft is a G1000 model, but not sure if has anything to do with it.

Cheers

AW

[longjon]

Sorry,, was that air conditioners? ACU??

which component

[airwrench]

sorry alternator control unit for the standby alternator system

Aw

[longjon]

ok then we bought a new from the factory 208 and the biggest problem was the autopilot, it would porpose up and down , was told its an inherant problem from the cheap Cessna autopilot system.

[airwrench]

yeah the old autopilots were junk, the ones on the G1000's much better

[fixin]

What leads you to beleive your Caravan is eating up ACU's. What Trouble Shooting have you done on the systems affected. Have you checked the alternator output against the generator output. The procedure is right in the book I cant remember the voltage split but it's in the book. You can check the Gen right off the GCU but ACU you will need to run wires off the Alternator into the cockpit, pull the pilots seat and run the airplane from the co-pilots side. With two multi meters and two people in the cockpit this job is no big deal. In the past adjusting the ACU to GCU voltage split has fixed the problems I have ran into with the STBY PWR problems of the Caravan. You can also build a break out box for these power generation systems it's in the M/M too but I have never had to go that far.

[Bulawrench]

service bulletin has been issued. I think CAB09-6. a free data card to insert and then a wiring change.

[airwrench]

yes checked gen and alt. outputs are within 1 v, gone through all the wiring as well. cab 9-6 is the sftware update, and cab9-8 the wiring mod. checking into these, the wiring mod may have been carried out but not the software update. thanks for input

[Bulawrench]

I will re-read those bulletins as the software must be done before the wiring.
I have the same issue on two aircraft. Fill out the form on the back of cab09-6 and Garmin
will send the card free of charge.

[revr]

what is the snag?
alternator will not come on line?
inop light stays on?
alternator will not come on line but inop light is off?
will the alternator come on line with the generator tripped?

a little more info will help.
have you checked into the diodes for the relay?
what about the drive belt tension. i have seen a couple times where the belt will slip on the alternator pulley.

ok then we bought a new from the factory 208 and the biggest problem was the autopilot, it would porpose up and down , was told its an inherant problem from the cheap Cessna autopilot system.

this sounds like a pitch servo problem.
the autopilot systems may be cheap but they work good if everything is working properly.