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Electrical failure trim circuit

f1rocket

f1rocket

Well Known Member
While doing my run up, I detected the faint smell of escaping electrons for a brief moment. My first thought was the regulator again. A quick check of the gauges didn't reveal any anomalies so I departed. Once airborne I quickly discovered that the trim wouldn't work. As luck would have it, guess which fuse is the only one that doesn't light up when blown? Yep the 2amp trim circuit.

The fact that I could smell electrons leads me to think there's a short behind the panel. I'll tear into it tomorrow. Anyone else experience a similar problem?
 
It sounds like an electronic component on Van's control board went up in smoke. Do you have the D-180 or SkyView?
 
I have the Skyview.

I suspect the switch module as well. It is very difficult to get out I discovered this morning. Basically it has to come out the front of the panel because it sits in front of the panel braces. Unfortunately that means removing the throttle and other cables as well. This is turning into a big deal now.

I guess it's a good time to swap out the old throttle for the vernier one.
 
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f1rocket said:
I have the Skyview.

I suspect the switch module as well. It is very difficult to get out I discovered this morning. Basically it has to come out the front of the panel because it sits in front of the panel braces. Unfortunately that means removing the throttle and other cables as well. This is turning into a big deal now.

I guess it's a good time to swap out the old throttle for the vernier one.
Click to expand...

I don't think it's on the switch panel. There is really only heavy duty stuff on that doesn't just burn up without blowing a fuse. My guess is that the black box which contains the electronic to convert your switch input for trim up/down into PWM pulses burnt out. That's where I would look first, probably by looking at the trim lines and see if there are any pulses and if they change pattern when the trim switch is actuated.
 
I'm confused. The fuse is blown and shorts immediately. I'm not sure what you are suggesting I check. Can you explain a little more? Thanks Torsten.
 
It is highly unlikely that the problem is within the AV-50001 SWITCH & FUSE MODULE. Just to make sure, disconnect the SWITCH D-Sub connector from the AV-50000A CONTROL MODULE, then see if the fuse blows. If not, reconnect the D-Sub connector.
It is more likely that the problem is within the AV-50000A CONTROL MODULE or the wires that go to the trim servo or the servo itself. To rule out the trim servo or its supply wires, disconnect the FUSELAGE D-Sub connector from the AV-50000A CONTROL MODULE. Now see if the fuse blows. If it does, the problem is within the AV-50000A CONTROL MODULE.
 
Thank you so much. In the hangar right now. I'll give it a go and report back in a few.

I pulled the switch d-sub but not sure it tested anything since there is no power going thru it so obviously, the fuse didn't blow. I reconnected it and pulled the fuselage d-sub and the fuse blew immediately.

So I can conclude its not the trim motor or fuselage wiring. What wires can I check going to the switch d- sub to determine if the control box is bad or some other component?
 
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The wiring diagram shows a trim speed controller. I assume it's built into the AV-50000A Control Module? Is that something that can be replaced without replacing the whole box? Have others had to replace the entire box before?
 
Do another check with the harness D-sub connected at the AV-50001 switch module but disconnected at the AV-50000 end (the switches D-sub connector).
If the fuse still blows then you have isolated it to a problem in that harness.
If it does not blow, then the problem is likely in the AV-50000.

It can be repaired.
If that looks like the problem, contact someone in tech. support and refer them to this thread to confirm what troubleshooting you have done, and then they will give you details regarding how to send it in for repair.
 
Randy,
From your test results, I'm pretty sure that the problem is within the AV-50000A Control Module. I have the D-180 system that is entirely different, so I do not know what is inside of the AV-50000A Control Module. But there is probably one circuit board that has all of various functions on it. If my D-180 control board blew the trim fuse, the LM7812 voltage regulator would be a suspect component.
 
I did receive a very brief "voltage warning" from the EFIS but it resolved itself too quickly and I didn't get a chance to investigate it. Think the VR might have done something to precipitate the problem with the trim or maybe vice versa?
 
Think the VR might have done something to precipitate the problem with the trim or maybe vice versa?
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No
The LM7812 is an electronic component, not to be confused with the alternator voltage regulator. I should not have mentioned that component which might not even be inside of the AV-50000. It is extremely unlikely that the Ducati voltage regulator has anything to do with the trim fuse blowing.
 
Another Option

Randy,

Another option: If you have an inkling of installing the Dynon AP panel this may be a good time to do so. The Dynon AP panel becomes the controller and current source for the trim motor after the circuit from the Switch Module?s 2 amp fuse is moved over to the AP wiring harness.

If you feel confident there are no shorts in the wiring to the trim motor and that the motor itself is OK, adding the AP Knob panel may be a cost effective way to go if all other functions on the AV-50000 are working OK.
 
John, thanks for suggesting that. Not a bad idea. The autopilot remote option is $950. Not sure what it's going to cost me to repair the AV-50000A unit.

Scott, do you have any idea ballpark? It's out of warranty so I know it's on me for the repair.
 
Randy,

Actually, if you are on a really tight budget you could get by for about half of the $950 because I believe I read in the SkyView manual the AP Panel works independently from the Knobs Panel, so they are not needed as a "pair" for the AP panel to work correctly ... so you could just install the AP Panel alone.

But being realistic, if the extra few hunderd is not an issue, may as well install the knobs panel as well.
 
Sorry but I'm not much of an electronics guy. A new box is $600 and with my fat fingers, I'm liable to botch things up. I spoke with Van's today and the box is on its way in. Estimate to repair is much less than the autopilot head so I'll take my chances with a repair unit.
 
Just heard back from Van's last night. Scott repaired my box. Cost is $225 plus shipping. They fixed it in a week. Overall, I'm not thrilled about having the failure but I am happy about Van's service and the fact that they are there, solvent, and available to help out. Thank you.

As an aside, there seems to be more than just a few others who have seen the same failure. I'm wondering if there's any idea on what is causing the short? Is there a component failure? Voltage spike of some sort? I'd feel better about the reliability of the box if I understood more about what caused it to fail.
 
f1rocket said:
Just heard back from Van's last night. Scott repaired my box. Cost is $225 plus shipping. They fixed it in a week. Overall, I'm not thrilled about having the failure but I am happy about Van's service and the fact that they are there, solvent, and available to help out. Thank you.

As an aside, there seems to be more than just a few others who have seen the same failure. I'm wondering if there's any idea on what is causing the short? Is there a component failure? Voltage spike of some sort? I'd feel better about the reliability of the box if I understood more about what caused it to fail.
Click to expand...

Randy, I would be interested in seeing the data that makes you think this particular failure is common....

I think there has only been one other failure with a trim control circuit in an AV-50000 box. I am saying that from memory without checking records so I could be off a bit, but with almost 450 Skyview avionics kits produced to date, it is a relatively low number regardless.
Edit - I did a quick check (there are records for every single box serial # listing anything that has ever been done to it) and I was wrong. There is no record of any other AV-50000 box being repair because of a failed trim control circuit. There are a few that required repair because the builder pushed excessively on the trim speed adjustment pot and damaged it, but no others that had an actual failure of the circuit

There have been quite a few people with trim problems (usually found at initial testing) that were convinced that it was caused by the AV-50000, but the actual cause usually ends up being wiring related, etc.

There have been AV-50000 boxes returned to Van's because the customer / builder is certain that it must be the cause of their trim not functioning, but the boxes check out fine and then they are forced to do some actual troubleshooting :rolleyes:) (everyone seems to always assume a problem must be related to a failure inside the box or switch module... in reality, most problems are related to wiring errors or poor/intermittent connections).

As for the cause of your failure? I don't know, but I can say that it is not anything that has been common.

You forgot to mention that the actual repair cost was $75 less than the estimate I gave you ;)
 
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Having just done the back end wiring for 2 12's, I am not surprised that problems stem from wiring issues.

The connector between the cable and the unit uses pins, the size of which I had never seen. I am fine with D-Sub connectors, I have the correct crimp but those little peskies...... I had a stand magnifier and a lupe in my eye to concentrate on those butt crimps ;)

As you terminate the D-Sub connectors in the kit, could Vans do those ones as well ?
 
mike newall said:
As you terminate the D-Sub connectors in the kit, could Vans do those ones as well ?
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Anything can be done if the right process is developed....

The reason those aren't pre-installed is because of the high risk of damage to the pins while routing the wires, and it would require a special part number servo for the RV-12 (with pins already attached).

They may seem like a pain, but they are very popular with home builders.....
do a search in the VAF forums on microfit connectors.

I think Section 5 of the construction manual has details/recommendations regarding an inexpensive crimp tool and the proper way to install the connector.
 
Yea, I have the correct tool - always a believer in that, it was just being able to see the little critters before you squeezed them that was challenging !

All pull tested satis and locked in place and function tested on the main power lines.
 
Well, I'm very happy that my failure is not common and that others have apparently not had similar problems. I have seen a few threads regarding trim issues but never really paid much attention to the final resolution. I appreciate your support Scott.
 
f1rocket said:
Well, I'm very happy that my failure is not common and that others have apparently not had similar problems. I have seen a few threads regarding trim issues but never really paid much attention to the final resolution. I appreciate your support Scott.
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No problem. I hope you are back flying soon.
 
To close the loop, I got my box back from Vans this week. I re-installed it, set the trim speed, and made a few adjustments to the audio inputs. In particular, I turned down the stall warning.

Man I was really glad to get back in the air. I missed it much more than I thought. Makes me glad I haven't sold it and makes me wonder whether I should even sell it. I love the 12. Just love it. I fly about 3-4 days a week and enjoy it very much.

I'm planning a quick trip up to northern Wisconsin to go lake trout fishing with my brother and son next month. Then I'll hunker down for the winter.
 
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