Trim Questio

[DavePage]

Hi All,

I've got a 94' Bravo, KFC 150 AP.  My elec trim works fine to trim down, but I have to use the manual wheel to trim up.  

Any advice where to troubleshoot, or do I head directly to the avionics shop without passing go or collecting $200.

Thanks & Merry Christmas

Dave

[N201MKTurbo]

It is probably your trim disconnect relay. So, yes head to the avionics shop.

[Fritz1]

or the trim switch, three microswitches in there, $30 each, one of them may be bad or wire broken off, however if the aluminum toggle is worn, no place to hide, new trim switch is about $2,500, you may be able to find a used one, but the toggle is probably worn, too, soldering a new trim switch is a bitch, requires dental skills, I practiced with my old worn out switch, subtle balance between the solder sticking to the posts and you frying the microswitches, avionics shop will be able to figure it out quickly, Merry X-Mas!

[IvanP]

I woud check the switch Fritz mentioned. I have reconditioned mine on 1990 Bravo, including the toggle springs, and it works fine now.   

[Fly Boomer]

44 minutes ago, IvanP said:

I woud check the switch Fritz mentioned. I have reconditioned mine on 1990 Bravo, including the toggle springs, and it works fine now.   

How does one recondition a spring?

[IvanP]

1 hour ago, Fly Boomer said:

How does one recondition a spring?

I reconditioned teh switch by replacing the springs  

[Fly Boomer]

10 minutes ago, IvanP said:

I reconditioned teh switch by replacing the springs  

Please elaborate.  Do you have a drawing of the switch, and a supplier for the springs?  The switches are nearly impossible to replace.

[IvanP]

1 minute ago, Fly Boomer said:

Please elaborate.  Do you have a drawing of the switch, and a supplier for the springs?  The switches are nearly impossible to replace.

I do not have a drawing or pictures of the disassembled switch. It was couple of years ago when I did this. The springs that return the split toggle switch into neutral position are just simple steel spring wires held in place by couple of pins. If I recall correctly, my hangar elf found some steel spring wire that was close enough to replace the tired original springs. Once you take the switch apart, the solution will be self-explanatory. It takes a little patience and skill to do and for someone inclined to tinker with small stuff, the repair can be a lot cheaper than $2.5k what Textron is asking for the switch now. The actual microswitches (3) that make up the assembly can be had from Mouser or other sources for about $30 or so.  

[Fly Boomer]

58 minutes ago, IvanP said:

The springs that return the split toggle switch into neutral position are just simple steel spring wires held in place by couple of pins.

Mine is working fine for now, but they clearly don't last forever.  I'm pretty sure I have some piano wire somewhere that was my grandfather's.  He would have done what you did -- take it apart, bend some new springs, and fix it.  Thanks!

[Fritz1]

yes to all, at $2.5k certainly worth disassembling trim switch, reinstalled best with pigtails that are spliced at the bottom of the yoke, anything in there is repairable or replaceable at little materials cost besides the toggle itself, I ended buying a new switch, there are two toggles, big one and small one, they hit the striker plates of the microswitches with a sharp point, once that point wears off friction increases and the spring cannot return the toggle which is sensed by the autopilot which then checks out, my smaller toggle was worn, if you have a used switch the larger toggle can be milled down to make the small one, same profile, I did not know all this when I started, took me about 20h to figure it out, find new switch and install, with hindsight I would have been better off having my favorite avionics shop do this, while I had the switch out I repaired the stripped threads in the plastic cap that carries the switch, glued in small nuts, think they were 2-56 thread, feels solid now and will probably last 2000h like the first switch