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Need help chasing electric gremlins

AHaury

AHaury

Active Member
I could use some input from anyone regarding a nagging issue that may have escalated to a big issue this past weekend. I've got a purchased-flying RV-6A, 557 TT on plane and new engine. Built in 2005, sold to second owner 2008, I picked it up in 2012 and I've put close to 200 of those total hours on it. The second-owner upgraded to a Tru-Trak but outside of that no electrical changes made. My only change has been to put in new stick grips with a new PTT switch which I did about 180 hours ago. The last IFR certification of the systems was done last year, conditional inspection is current as of Oct 2014.

I'm having electrical issues now that I can't pin down. I've had difficult cranking at times (turn the key, just hear a click, turn it back, it starts slowly). Pulled the battery, it seemed to test fine. Coupled with that I've had 3 issues where everything went off, then back on. Like I flipped the master switch off, then on. I one situation I was on an IFR plan and ATC didn't ask about losing transponder it was that quick. The first time I thought I had bumped the switch or something. The last time this occurred just as I hit the PTT switch. I've also noted a low voltage reading in flight at times. Again, the last time this "outage" occurred the voltage was reading low, as I hit the PTT, everything clicked off/on, and when the panel came alive again, the voltage went into the normal range.

I've gone out for hours in the local area trying to determine what is happening. The last situation occurred yesterday as I was turning onto the runway, full power and had an incredibly strong electrical burning smell. I aborted, back to the ramp, pulled the cowl, could find nothing that even appeared to have been hot. Put it all back together, started right up. Flew for 15 mins no smell.

I read Paul Dye's recent post about the starter solenoid and that is another check to make. I'm not very electrical smart, but need some basic suggestions on where to start. Talk slow...
 
AHaury said:
I read Paul Dye's recent post about the starter solenoid and that is another check to make. I'm not very electrical smart, but need some basic suggestions on where to start. Talk slow...
Click to expand...

Or, the master solenoid.

Cheap in the overall scheme of things to just replace.
 
Master solenoid 1st. Starter solenoid is only to spin the starter and should not affect the other electrical systems. But like Mike said, cheap to replace both.

:cool:
 
Could also be the master switch or key switch if so equipped. I would guess master solenoid first.
 
AHaury said:
The last situation occurred yesterday as I was turning onto the runway, full power and had an incredibly strong electrical burning smell. I aborted, back to the ramp, pulled the cowl, could find nothing that even appeared to have been hot. Put it all back together, started right up. Flew for 15 mins no smell.
Click to expand...

Listen to your airplane, my suggestion is you quit flying the bird until you sort out the problem and especially what was burning! Problems never miraculously fix themselves. Continuing to fly an aircraft with a known issue is just asking for trouble. :eek:
 
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It is interesting that you had both a starter issue (slow cranking which is common sign of a weak battery but said your battery tested fine) and total power loss while in flight. Usually those two systems are separate from each other. You should have a starter solenoid installed between the battery and the starter, this allows you to run a smaller gauge wire up to your ignition switch and usually just provides a ground to the solenoid to allow a direct path current to the battery through the ot gauge wire installed. The other solenoid is your master solenoid which allows your aircraft to power up from a master switch when engaged in the same fashion.

From what you are describing this is where I would begin if I were troubleshooting a customers aircraft brought into my shop. The burning smell could have come from one of the solenoids but I feel is a result from another issue in the other aircraft. Have you checked the output of your alternator? It sounds to me that your alternator is failing intermittently (from you comment of noticing a low power output at times) or it is not failing completely but is only outputting a lower voltage (which is why you may have not noticed a warning light on your panel). Have you checked to make sure your belt is tight enough and not slipping which can give the sign of a week alternator. If you were experiencing a lower than normal voltage, it would not be charging your battery and when you pressed the push to talk switch on your stick, there was enough of a voltage drop across the system to power the transmit side of the radio, that there was not enough voltage to keep the contactor solenoids closed and therefore the solenoid opened causing a power failure. When you released the PTT voltage came back up enough to possibly reconnect the solenoid and provide power again. I have seen this before where the voltage was right at the point where the solenoid was opening and closing very quickly due to voltage fluctuations causing the contacts inside to weld themselves together and create a burning smoke smell in the cockpit. Found the alternator wasn't dead but very weak.

Checking the alternator and then checking your grounds on the aircraft as corrosion possibly between grounding straps and frame could produce to high of a resistance path.

Electrical gremlins can sometimes be the worst and hardest to troubleshoot in experimental aircraft because no two airplanes are wired the same and you being the second owner doesn't help just in the fact that you didn't put it in so the original builder could have done something different. Without seeing your aircraft in person, this is the best that I could possibly come up with. Hope it helps!
 
BobTurner said:
check all ground straps, especially at the battery, for corrosion. Check both ends.
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I second this and it's worth check the alternator as Patrick said also. It sounds to me like very possibly a loose or corroded wire that sometimes makes contact and other times not.

I had a weird problem with a first engine start where we had been running the panel without problems for hours, then we cranked the engine and it fired right up, but then the panel powered down and the Dynons went into backup battery mode. In the end, the ground wire from the battery to the airframe was bolted through a hole drilled in a plate, but the paint wasn't scraped off, so the only contact to ground was the edge of the inside of he hole to the bolt. When we cranked the engine it arced and burnt the contacting portion and then everything was dead. Removed the paint around the hole for a good ground contact and replaced the bolt and the problem was solved.
 
Check the tension on the alternator belt. If that is fine your alternator is likely on its last leg.
 
Master solenoid and battery ground.
Then both wires coming off of master solenoid.
 
AHaury said:
had an incredibly strong electrical burning smell.

I'm not very electrical smart, but need some basic suggestions on where to start.
Click to expand...

A burning smell....whoaaa. I recommend that if you are not, by your own admission, savvy about electrons, then get out your cheque book and engage a professional. An avionics pro will probably locate your problem in a few minutes. Left to your own devices you might just end up with an inflight fire or an avionics failure during an IFR flight (or both !!!).
 
Something loose

Also, remember there are so called crimps in those heavy power wires. The standard pull test for a AWG2 termination is 500 pounds, yes, five hundred.

Think about where the power goes, and what the starting and power supply function have in common. Check everything, look for shorts, wrench, pull (hard) and wiggle every single connection. Power and ground side. This is just to begin.

You can check charging after finding the source of the disconnects. If you don't have a good handle on how to do the diagnostics, and proceed with a definitive plan, then employ a qualified person to lead the effort. (or keep asking here :)) Guessing will let to several expensive parts replaced until someone stumbles on the real cause. Don't assume anything.
 
Edit, saw Bill's post above after I typed this, so here's my sample of what he was talkin' 'bout… ;)

Another item you might add to the list of checks is the wire crimps on the related wire fasteners. I had a wire break inside a spade fitting on my original alternator, which caused intermittent drops to zero amps (and the resulting drain on the battery and electrical system). Looked fine from the outside, but in flight it would vibrate loose at times. A gentle "pull check" found it, and solved the mystery. So along with the components all have listed to check, I'd just add the wires and fasteners. Good luck!

Cheers,
Bob
 
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BillL said:
Guessing will lead to several expensive parts replaced until someone stumbles on the real cause. Don't assume anything.
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Roger that. Hope is a horrible strategy. I have today off and the prediction is rain so off to the hanger to start checking things.
 
electrical Gottchas

Please first confirm that the ground from battery negative to engine block is less than 3 milliohms and that the airframe to negative post is the same or less. The engine controls i.e. throttle, mixture, and prop becomes ground and can get very hot if the engine to airframe ground id not correct. Note that the lack of good negative connection is often a source of the issues you describe. Electrons flow from negative to positive.

After determining the negative connection is good move to the master then starter solenoid. There the best best method is remove and replace as the cost low compared to alternator regulator issues. The suggestion about the alternator connections are the net step.

Tyler
A&P, FCC GROL
N174MT
 
solenoids

I'll just throw this out there for consideration. I have actually seen this on an airplane in our shop. Master solenoids are designed for continuous duty. Starter solenoids are for short engagements. I saw a case where a starter solendoid was installed as a Master. It worked for awhile but began giving trouble after a few hundred hours.
 
To add to the good advice already given.

You may just have more than one discrepancy. Best to check all the way through these primary circuits from battery to ground, battery to starter, alternator to battery and primary bus. You may find several termination points that can be cleaned and/or tightened, reducing resistance and increasing voltage available.
 
Something is burned

Suggest that you don't fly until you find and replace the burned component. This may be in addition to the real cause of your problems. Also, look for the reason that the burned component apparently wasn't fused properly. You don't have to look 'way out there' for the solutions to these problems - they are right there in front of your nose - use it to help you find the burned component. Good skill!!!
 
TylerII said:
Please first confirm that the ground from battery negative to engine block is less than 3 milliohms and that the airframe to negative post is the same or less.
Tyler, these connections are secure, but how is that checked?

Thanks to all for the input and for those who are "plight following" here's an update. Pulled the cowl this morning and started at the battery checking all connections. Didn't take long to find a loose connection between the starter solenoid and the connection on the firewall. This also has a score mark on it like it may have sparked. Cannot find anything that even looks like it was burned or hot. Looks like I probably have a loose alternator belt also.
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Click to expand...
 
Well you certainly got everyone's attention with the burning. That sounds serious and you should definately find that before flight as others have mentioned.

To me it sounds like you might have a couple of problems, but its hard to say. The burning problem and the other one they may or may not be related. The first thing I noticed in your description was that you said you checked that the battery was ok. How did you do this? Checking the voltage is not a sufficient test of a battery. It would need to be tested under load in some manner. Is this how you checked it?

Now the burning problem. If you can smell it in the cabin then its not just a little spark. Loose connections or broken wires cause a higher resistance and will often spark. This sparking can melt the individual strands of the wires and intern cause higher resistance and more heat. More heat means even higher resistance and it just keeps getting worse until the wire melts or the circuit protection (fuse or breaker) limits the current. As others have mentioned there are some high current paths that don't have protection like the battery ground strap. I would carefully look around. You will see some burnt wire or a connection to the frame with carbon on it. Personally I would check the wire that turns on your master solenoid.
 
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rapid_ascent said:
The first thing I noticed in your description was that you said you checked that the battery was ok. How did you do this?
Click to expand...

I took the battery to a local battery shop to have it checked on one of their test machines.

Yeah that burning smell got my attention also. Still a few things to check as far as sniffing for evidence of what caused it. Spent a fair amount of time up-ended on my back looking behind the panel but saw nothing that seemed out of order there. Thanks, I'll give another look at the wiring that runs the master solenoid.

Headed back to the hanger for more...
 
I?m probably coming in a little late but in case no has mentioned it among the numerous excellent suggestions for direction, I encourage you to remember the old adage ?Do one thing at a time, do it very well, check what you have done and do it over if not either perfect or nearly perfect, then move on??or put another way - confirm to a certainty that each item or thing of interest works perfectly and if not fix it to a certainty, double check it, then write down what you have done, and move on to the next thing.

Keep us all apprised as I think your issue(s) has raised a lot of interest.
 
+1 on the crimps ....

BillL said:
Also, remember there are so called crimps in those heavy power wires. The standard pull test for a AWG2 termination is 500 pounds, yes, five hundred.

Think about where the power goes, and what the starting and power supply function have in common. Check everything, look for shorts, wrench, pull (hard) and wiggle every single connection. Power and ground side. This is just to begin.

You can check charging after finding the source of the disconnects. If you don't have a good handle on how to do the diagnostics, and proceed with a definitive plan, then employ a qualified person to lead the effort. (or keep asking here :)) Guessing will let to several expensive parts replaced until someone stumbles on the real cause. Don't assume anything.
Click to expand...

In the middle of doing a lot of electrical work on my RV8 (purchased). Just about everything with electrons is being changed.

To my GREAT SURPRISED I noticed that the crimped lug on the positive battery terminal had FALLEN OFF!! And it had a nice looking hexagonal crimp with heat shrink. Looked great.

Had had some slow starting issues earlier and decided to just get a new battery. That loose crimp MAY have been my problem.

It sure was GOING TO BE a major problem some time in the future as a lot of thing depend upon that connection remaining true.

Try to rip them all apart with your bare hands.

James
 
One of my first thoughts when I read your original description of the problems you were experiencing was that your alternator belt was slipping. I wonder if you were smelling burning rubber rather than burning electrical? Either one will really get your attention!

I've had two alternator failures that caused belt slippage and an intense burning smell, both times over water (of course). Popping the master turned off the smell almost immediately.

If your belt is loose it can slip when you have everything powered up or your battery charge is low.
 
"Personally I would check the wire that turns on your master solenoid."

If properly wired, the wire that turns on the master cyl, is a ground wire, and not subject to burning.
 
Tugged and tugged

Thanks to all those who took the time to offer wise and much appreciated advice. If you're in Fayetteville, beer is on me.

I spent another couple of hours this evening tracking wires, pulling on every connection under and behind the panel and engine area, and have checked all the points people have suggested. Even removed the grips and inspected the wiring in the sticks. Unfortunately (?), no brittle coatings or anything burnt looking. I wish I had found something to explain that smell.

In total I found two issues: the loose alternator belt, and the loose power cable leading to the starter. Fixed both and did a ground run up with everything electrical running. Nothing out of place or smelling funny in the cabin. The only thing suggested that I haven't done yet is just replace the master solenoid. Leaving town tomorrow so I'll have to pick up the trail after Sunday.

Thanks again all.
 
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