Trim Tab Indicator Failing

[Ted Christopher]

Last flight my trim tab was operating normally using the switch, but I could not set it for takeoff as the trim tab indicator on the Skyview Touch screen was not working, the bar stayed at the bottom of the graph except for a few minutes when it was functioning normally. All other readings on the Skyview seemed normal. This is a factory built RV12 SLSA.

I'd like to check the connections, can I access these by removing the tail cone or will I need to block up the rear of the plane and climb inside. Can anyone suggest what might be going on other than some corrosion in the connection?

[bobg56]

I had a problem were the trim worked but indication was erratic, look in tail cone and check connections. They used a connector block which is not a great way to ensure a solid connection, I soldered the wires and covered in heat shrink, end of problem.

[Bob Y]

The trim servo and associated connector are inside the tail fairing, so you should be able to determine if the problem is there fairly easily.

[Ted Christopher]

Thank you both, I probably can't solder since this is a SLSA and not a ELSA, but I will clean the connection. I've heard some posts refer to a spray for electrical connections, do you know what it is called?

[DHeal]

I've used DEOXIT with apparently good results. Often just sliding the contacts around creates an improved connection.

https://caig.com/deoxit-d-series/

[RFSchaller]

If it?s an SLSA you could ask Vans for approval to solder and that would be legal if they approve.

[rongawer]

First off, have you physically cycled the trim servo while on the ground? If it’s moving correctly full cycle in both directions, then it’s the trim indicator or connection. If it’s not moving correctly, then it’s off to the troubleshooting races.

If it is corrosion, any good contact cleaner will do the job. They sell CRC Contact Cleaner at AutoZone if you have one near you, or Walmart for that matter.

The thing is, if the issue really is corrosion, you want to prevent it from happening again, so when you reassemble it (or any electrical connection/connector plug for that matter), fill the female plug with a silicon dielectric insulating compound; it will protect and lubricate the contacts and prevent water and oxygen intrusion to the contacts mitigating further corrosion. I recommend Dow Corning DC-4, which has been an a great product for many years. You can buy it off of Amazon and 5 oz tube will be lifetime supply for most folks. The good news is that the shelf life is about that too. As a bonus, it’s a perfect rubber protectant as well; useful for wiping down all of your rubber seals (car doors...) and installing o-rings as well.

While the tail-cone connector is an easy place to start, don’t forget to check connections all the way to the switch and indicator. The simple action of disconnecting, spraying with contact cleaner, applying DC-4 and reinstalling at all points might solve it and is good preventive maintenance too.

Molex style connectors work well, but a little corrosion protection never hurts. If redoing the connector at the trim servo doesn’t do the job, then you need to start basic electrical troubleshooting, which is bisecting the circuit, test connections and components, eliminating the good ones until you find the fault.

The most likely fault is the connections of the circuit or the trim switch, keeping in mind that whatever gets used the most, wears the most. If those prove out, then just keep testing and eliminating the good components from the puzzle. Happy hunting.

[NinerBikes]

Originally Posted by rongawer

First off, have you physically cycled the trim servo while on the ground? If it’s moving correctly full cycle in both directions, then it’s the trim indicator or connection. If it’s not moving correctly, then it’s off to the troubleshooting races.

If it is corrosion, any good contact cleaner will do the job. They sell CRC Contact Cleaner at AutoZone if you have one near you, or Walmart for that matter.

The thing is, if the issue really is corrosion, you want to prevent it from happening again, so when you reassemble it (or any electrical connection/connector plug for that matter), fill the female plug with a silicon dielectric insulating compound; it will protect and lubricate the contacts and prevent water and oxygen intrusion to the contacts mitigating further corrosion. I recommend Dow Corning DC-4, which has been an a great product for many years. You can buy it off of Amazon and 5 oz tube will be lifetime supply for most folks. The good news is that the shelf life is about that too. As a bonus, it’s a perfect rubber protectant as well; useful for wiping down all of your rubber seals (car doors...) and installing o-rings as well.

While the tail-cone connector is an easy place to start, don’t forget to check connections all the way to the switch and indicator. The simple action of disconnecting, spraying with contact cleaner, applying DC-4 and reinstalling at all points might solve it and is good preventive maintenance too.

Molex style connectors work well, but a little corrosion protection never hurts. If redoing the connector at the trim servo doesn’t do the job, then you need to start basic electrical troubleshooting, which is bisecting the circuit, test connections and components, eliminating the good ones until you find the fault.

The most likely fault is the connections of the circuit or the trim switch, keeping in mind that whatever gets used the most, wears the most. If those prove out, then just keep testing and eliminating the good components from the puzzle. Happy hunting.

Ron, off the top of your head, since I've had the tailcone off and ran a DMM off the connectors near the trim motor and everything was good, voltage of 5V down to near zero then up again, end to end.

How many other electrical connectors are there to check, forward of the tail cone assembly. I'm helping out a 72 year old friend, he's not as flexible as he once was, but he built the plane, I didn't.

And the locations? I assume check at the back of the Dynon D1000 Touch, and are their any other black boxes that connections go into also?

I also need to pull the red cube for GPH flow for him and get that working again too. Have De Oxit., but dielectric silicone grease sounds a whole lot better.

[Mich48041]

Pitch Trim Potentiometer
_
5VDC: EMS-220 pin 18, AV-50000A EFIS pin 50, AV-50000A Fuselage pin 22
_
Signal: EMS-220 pin 23, AV-50000A EFIS pin 30, AV-50000A Fuselage pin 4
_
GND: AV-50000A Fuselage pin 25

[NinerBikes]

Originally Posted by Mich48041

Pitch Trim Potentiometer
_
5VDC: EMS-220 pin 18, AV-50000A EFIS pin 50, AV-50000A Fuselage pin 22
_
Signal: EMS-220 pin 23, AV-50000A EFIS pin 30, AV-50000A Fuselage pin 4
_
GND: AV-50000A Fuselage pin 25

Where is that Engine monitoring module normally installed and located in an RV-12? And generally, how does one access it? Pull part of the instrument panel?, or is it mounted behind the glove box, or ???