Amperage spike at full power

[gulfportflyer]

Hi CT owners!

I am the relatively new owner of N169CT, a 2006 CTSW and am a student pilot.

I’ve been flying the aircraft since purchasing it in May 2020 and the only issue has been a defective ignition module which was replaced by the seller. Other than that no issues until now.

When flying closed traffic recently, we saw an amperage spike ranging from +15 - +20 and the alarms on both Dynon devices (D100 and D120) went off. The spikes were not consistent and would cease if power is reduced. 

We immediately landed and proceeded to do a run-up to 3200 (our normal run up) and to 4000 and there was no issue. We then went to take off again, as soon as full power was applied we got a spike and alarm. The takeoff was aborted and we brought it back to the hangar where it sits now.

After going through many articles with seemingly similar issues, we spent the last two days checking every ground connection we could find and ensuring nothing was loose. We also checked continuity of the ground from the Dynon D120 chassis to the engine mount and it is fine. 

Our mechanic is off this week so we’re on the ground until he is back on Monday, but if anyone here has any ideas, your suggestions would be greatly appreciated! Thank you!

Seth - N169CT 

[gulfportflyer]

11 hours ago, Roger Lee said:

If you have the Dynon instruments then remove the left panel. In the back is the shunt. Remove the two small screws on each end and clean those wire eyelets with a scotch pad and where they screw down to. The fasten those two wires back down. Also you have 5 ground wires. 4 in the engine compartment and one behind the right panel that should have a wrench put on them. They may be hand tight, but wrench lose.

Hi Roger! Thank you for your reply. I was suspicious of the shunt as well and hope to check that today. We’re going to do a test high speed taxi first to see if anything we did yesterday on the right side had positive results. I’ve also added a picture of the right side. If you see anything out of order, please share your comments. Thank you! 

[Tom Baker]

Make sure the bolt on the odd shaped metal plate with the Flight Design sticker that has all the terminals attached is tight.

[Skunkworks85]

12 hours ago, Roger Lee said:

If you have the Dynon instruments then remove the left panel. In the back is the shunt. Remove the two small screws on each end and clean those wire eyelets with a scotch pad and where they screw down to. The fasten those two wires back down. Also you have 5 ground wires. 4 in the engine compartment and one behind the right panel that should have a wrench put on them. They may be hand tight, but wrench lose.

The shunt is on the left side dynon?

[johnnyjr]

I recently had a ground issue and it was the wiring that jumped the engine block to the engine mount.  I would make 100% sure that the FWF grounds are on and solid, if they look dirty it's def worth a clean up, if not for the present issue to help prevent future issues.

The reason I brought this up is that all was functioning fine on the ground and while the plane was still cool.  After 45 mins or so of cruise flight once everything heat soaked I would have random issues with gauges, and not being able to shut the engine off with the key.  This was all because I have a un-attached ground wire.

[Tom Baker]

2 hours ago, Skunkworks85 said:

The shunt is on the left side dynon?

On the firewall behind the left side Dynon.

[gulfportflyer]

17 minutes ago, johnnyjr said:

I recently had a ground issue and it was the wiring that jumped the engine block to the engine mount.  I would make 100% sure that the FWF grounds are on and solid, if they look dirty it's def worth a clean up, if not for the present issue to help prevent future issues.

The reason I brought this up is that all was functioning fine on the ground and while the plane was still cool.  After 45 mins or so of cruise flight once everything heat soaked I would have random issues with gauges, and not being able to shut the engine off with the key.  This was all because I have a un-attached ground wire.

Hi Johnny! That’s actually what we were looking for yesterday. More pictures attached of engine compartment here. Please let me know if you spot anything, but we traced every known ground wire and all were secure. Thank you!

[ODowneyEng]

ROGER IS ON HIS GAME

I came across this same issue on a couple of occasions while working on LSAs. Each time it was the shunt. A visual check is useless.

1) Take pictures before disconnecting wires.

2) Mark wires before disconnecting.

3) Clean shunt and wire End rings with the brown scotchbrite.
4) Cover all parts with Vaseline.

5)Reassemble using new lock washers.
Don’t use ACE AVIATION HARDWARE.and don’t forget your other instrument Senders connectors while at it.

 Vaseline was a priceless part of my electric toolkit in my Marine work. It keeps the oxygen out

[gulfportflyer]

1 minute ago, Odowneyeng said:

ROGER IS ON HIS GAME

I came across this same issue on a couple of occasions while working on LSAs. Each time it was the shunt. A visual check is useless.

1) Take pictures before disconnecting wires.

2) Mark wires before disconnecting.

3) Clean shunt and wire End rings with the brown scotchbrite.
4) Cover all parts with Vaseline.

5)Reassemble using new lock washers.
Don’t use ACE AVIATION HARDWARE.and don’t forget your other instrument Senders connectors while at it.

 Vaseline was a priceless part of my electric toolkit in my Marine work. It keeps the oxygen out

Thank you Odo. Are you literally suggesting to cover the whole shunt with Vaseline after cleaning?

[johnnyjr]

The pics don’t look off. What I can say if the cable that I found not attached was located under the engine mount near the front wheel bracket. There should be a few jumpers that go engine, frame then frame to next point until it gets to the battery and ground block inside. 

[ODowneyEng]

Just the wire connecting points. You don’t want to have oxidation between wire connectors and Shunt

[gulfportflyer]

1 minute ago, Odowneyeng said:

Just the wire connecting points. You don’t want to have oxidation between wire connectors and Shunt

Got it! Thank you again!

[ODowneyEng]

For years Detroit Automakers used Vaseline in bulb sockets.

Put it in ship Navigation lights, lasted years in saltwater environment.

[Tom Baker]

1 hour ago, Roger Lee said:

Use dielectric grease. Vaseline is also flammable. It will burn. Put a match up to a char of it. You don't need grease all over it. Just at the contact points.

Yep, I saw a survivalist using cotton balls covered with Vaseline as a fire started along with a magnesium fire stick.

[Skunkworks85]

14 hours ago, Odowneyeng said:

For years Detroit Automakers used Vaseline in bulb sockets.

Put it in ship Navigation lights, lasted years in saltwater environment.

Being an engineer at the largest OEM automotive lighting supplier. I have never heard of Vaseline being used. But that doesn't mean it wasn't used decades ago. If this was truly a value added process, I am 100% confident that it would still be an accepted practice, and it is not for many, many reasons today.

[Jim Meade]

Stabilant22, if you can afford it.

[sandpiper]

On 7/28/2020 at 7:20 PM, Tom Baker said:

Yep, I saw a survivalist using cotton balls covered with Vaseline as a fire started along with a magnesium fire stick.

My survival kit, years ago, had the  cotton balls you describe. Kept them in 35mm film canisters that used to be so plentiful.

[gulfportflyer]

Hi everyone! I want to share a couple of updates. First cotton balls and Vaseline definitely great fire starter. Second after removing right panel and checking all grounds test flight did not experience the issue nor have subsequent flights. We were already due for a 35 hour oil change and have a new LED landing light and other minor items (including cleaning of ammeter shunt on left side) to address so will definitely be asking for a thorough look at our 35hr oil change this week. I also now have a rectifier on hand ensuring that if the current unit does not test 100% we can replace during this maintenance event. Thank you to everyone for your help advise and comments here!

[gulfportflyer]

12 hours ago, Roger Lee said:

If you haven't you still should clean the shunt wires.

Hi Roger! As noted above, I am definitely going to ask the mechanic to do that during the upcoming maintenance. Thank you again!

[Isham]

Does anyone have a photo of the ammeter shunt?

[ODowneyEng]

 

Remove screws one at a time, clean and cover with dielectric grease.

That way no mistakes reconnecting 

located behind Dynon

 

[Isham]

Thank you for the photo.  I am planning to open it up tomorrow and now I know what I am looking for.

[ODowneyEng]

Your welcome, let’s all know how you make out.

[Isham]

GOOD GRIEF!  I cannot believe the hidden corrosion under the two larger (outboard) terminals.  I'm surprised that any current was flowing through them.  The small wire center terminals were not too bad.  The outboards bigger terminals were so bad that I could not get it cleaned off with a scotch brite pad.  Ended up using my DOTCO with a scotch brite green wheel.  Put on some diaelectric grease so it should be good to go.  It's too gusty (for me) here in central Kansas for the next few days but as soon as I can I will try it out in the air.  I expect this was my problem.

If I was in charge of Flight Design I think I would be incorporating a few cents worth of diaelectric grease in production to avoid problems like this in the field later. 

I really appreciate this forum and the expert advise from the dedicated members.  We all go through a learning process when we have issues, but the advise here is invaluable for keeping our airplanes from becoming hangar queens.  Thanks.

[Anticept]

DC 4 (Dow Corning 4) is a wonderful dielectric grease.

I do want to point out to people who might swing by to read this, and wonder "Why Dielectric Grease? Doesn't that INCREASE resistance?" The answer is yes, IF you didnt tighten them down properly. DC4 is sticky but also really fluid, and it will squeeze right out from between the metal to metal contact.

Never use a conductive grease because of the risk of shorting. Also, never use dielectric grease on any connections that transmit data or radio, it changes the capacitance of the wire.