Electrical Problem - Main Circuit Dead

[Tom Baker]

One thing that concerns me is you said that your CB master switch has been replaced with a toggle switch. If the toggle is not also a CB type switch you are setting your self up for trouble. It was set up that way to protect the whole system. I doubt that it is the different switch though, unless there is a short in the wire that goes to the starter solenoid. Does the engine turn over by hand OK? If it does I would try removing the starter wire and checking things with it disconnected. If your battery voltage is dropping off in a big way when you do this then it almost has to be a short in the starting system.

[Steven]

Thanks for all the suggestions. I will relay them to the mechanic when he begins doing diagnostics, hopefully this coming week ! Disconnecting the starter wire for a test sounds like an excellent idea. One concern about the diagnostic process is that the failure happens only once and then the entire electrical system remains dead for a period of time. It then recovers, as though a circuit breaker resets itself. I don't know if that takes many minutes or hours, but it's not just a few minutes. It may hinder the diagnostic process. Any ideas of what's behind the mysterious recovery ???

 

As for the new master switch, yes I think it has a circuit breaker. I was reluctant to replace the original, but the mechanic gave me a sales pitch so I went along with it. Supposedly it's a better switch, so it must also include a breaker.

[mocfly]

Steven,

A competent mechanic should be able to look at the electrical prints on our aircraft and troubleshoot this in less than an hour. I bet your mechanic who changed the switch to something other than a stock item never made the appropriate electrical print change. This new addition or change to the electrical circuit should be the first thing relayed to the person who will be looking at your aircraft.

Chris

[Roger Lee]

Hi Steven,

I agree with Chris. I would look at what was maintenanced last and that is the switch.

[Steven]

The switch was replaced about 3 years ago, so it's not a recent maintenance item, and has been functioning well thus far. Perhaps a problem has developed with the switch, but I'd guess that it's elsewhere. However I'll certainly alert the mechanic who works on this to check the switch early on in his diagnostics in case that's where the problem is.

[mocfly]

Steven,

Please keep us informed with what you find. If there is something in the switch that would be especially important to know for this group as others may try to replace stock switch

with said switch.

Good luck.

Chris

[Steven]

I'll certainly keep this thread updated with any new developments, but at this point there unfortunately are none. I'm waiting for a mechanic to be assigned to do the toubleshooting, hopefully by later this week !

[ozairangel]

I think there are quite a few of us waiting to hear the outcome of this one......

[Steven]

A mechanic with electrical skills who works for the military at Stewart Airport is going to drive down to HPN (3 hour round trip) to troubleshoot my electrical system, hopefully this week. Evidently it's an issue of FAA regulations and that authorization to work on the plane had to be specifically provided by Flight Design USA. So I presume the local mechanics didn't meet the electrical skill set requirement to get authorization to do the work.

 

It may be a relatively simple problem and this certainly demonstrates the difficulty, at least in my case, of having basic maintenance and repair done on the plane. I wonder if others have had similiar experiences ??? Fortunately I don't really mind if it's expensive to repair. The way I view it is that I paid $145,000 for the plane four years ago, and if this costs as much as 3% or even 5% the cost of the plane, that's still reasonable in the big picture.

[Mike Koerner]

Steven,

 

There is another type of short circuit protection called a Thermal switch. From Wikipedia:

 

A thermal switch (sometimes called a thermal reset or thermal cutout) is a device which opens at a high temperature (often with a faint "plink" sound) and re-closes when the temperature drops. The thermal switch is a bimetallic strip, often encased in a tubular glass bulb to protect it from dust or short circuit. Unlike the thermal fuse, it is reusable, and is therefore suited to protecting against temporary situations which are common and user-correctable.

 

A thermal switch could take 10 or 15 minutes to cool down sufficiently to re-close. But I don't think they are normally used in airplanes where you might not have 10 minutes to wait. I think circuit breakers are most commonly used, since the can be reset instantly. However, as a last ditch back-up, perhaps one has been buried inside the starter motor.

 

Mike

 

 

 

[Steven]

It would seem there must be a thermal switch somewhere, but if it were in the starter motor it would presumably effect only the ignition circuit, not the main circuit. The recovery of the main circuit is certainly a mystery.

 

I talked with the mechanic who is going to troubleshoot the problem today on the phone. He works full time at Stewart Airport, but also part time at Westchester Airport where my plane is based. So it's not a special trip down for him. I think he plans to work on my plane later this week or early next week.

[Steven]

The mechanic worked on my plane late this week and found a loose electrical connection on the starter relay (solenoid). He said the negative lead was loose and after tightening it the engine cranked. However, evidently due to repeated failed starting attempts and running the electrical system, the battery could not crank the engine fast enough to start it. He recharged the battery overnight and the engine then started successfully.

 

I'm rather baffled by the symptoms, given that this was the root cause. It's very mysterious to me that the whole system would go dead just because of a loose lead on the solenoid.

 

Another issue I'd like to understand better is battery strength and how to measure it. A voltmeter evidently can show the battery producing 12 or even 13+ volts and yet the battery is weak. I bought an inexpensive load tester which puts a 100amp load on a battery. I took a fully recharged old battery that was reading 13.4 volts on the meter, but that dropped to around 9 volts under the 100amp load. The 9 amp reading was considered "bad to weak". Yet going by just the voltmeter or the charger, the battery was fully charged. haha.

 

Another question I have is whether I can use a car battery jump starter that generates peak amps of 300+. Is that safe to use on the CTLS or could it somehow damage the electrical system ??? Just $39 and it could come in handy for the car too -

 

http://www.amazon.com/Stanley-J309-300-Jump-Starter/dp/B001U04NCA/ref=sr_1_3?ie=UTF8&qid=1336240163&sr=8-3

[chanik]

The catch here is that you cannot, with normal sized wires and ordinary clip leads, make a decent connection to handle 100Amps. You need very thick, 8AWG wires and strong, knarly gripper clamps to get close to that with small connection loss. So the little wire/exhaust stack connections, while fine to charge a few amps, are not adequate for jump starting. Steel is a bad conductor anyway.

[Roger Lee]

Hi Steven,

 

This is why most of us with a lot of experience with composite planes like the CT will tell you anytime you have an electrical problem check all the grounds first.

Kurt is right about the amp loading, but to answer you other question is yes you can use a car battery to start the CT. 12V is 12V and the Rotax starter pulls at least 70 amps on start. The wire out the bottom of the plane is for charging or jumping. The is the positive lead, then connect to the muffler for the negative ground.

[chanik]

But you won't get anything close to 70Amps through that muffler/wire hook-up. You can charge a dead battery that way but not with another battery; you need a running voltage closer to 14V for that. So having a big car battery and jumper cables won't get you started if you have a dead battery. If you could get some solid, direct connection other than the muffler it might work but I think you would need to pull the cowl and commect right to battery - or the grounding strap from the battery. Something very low-loss like that.

[Roger Lee]

Hi Kurt,

 

I have started 4-5 CT's with a car and their jumper cables on batteries that wouldn't do anything but make a clicking noise. These batteries were pretty dead. I jumped one dead CT with the cowl off, just a battery form my fuel cart and the auto jumper cables directly to the dead battery terminals. I'm not by any means an electrician and don't know any loading and amp delivery specs, but these did work okay.

[chanik]

I was skeptical so I took my milli-ohmeter out to the plane. The stacks measure 82mohms to the battery negative through the engine case. Not good, but much better than I thought. So looks like you can jump it with good cables. It would be anemic, but probably more like 30A is really what the starter wants. So with contact losses, you will end up with 4-5V of line loss and 8V at 30Amps delivered to the starter.

[Tom Baker]

I was skeptical so I took my milli-ohmeter out to the plane. The stacks measure 82mohms to the battery negative through the engine case. Not good, but much better than I thought. So looks like you can jump it with good cables. It would be anemic, but probably more like 30A is really what the starter wants. So with contact losses, you will end up with 4-5V of line loss and 8V at 30Amps delivered to the starter.

 

For jumping you don't need to worry so much about the path to the battery. In fact you could remove the ground wire from the battery and still be able to jump start. For cranking you would just need to worry about the resistance between the exhaust and the starter.

[Steven]

Good news and bad news.

 

The good news is that I was at my plane this evening and it started easily. So I'm very glad about that !

 

The bad news is that my Dynon EMS (engine monitoring system) is screwed up. I'm getting invalid readings from most of the CHT and EGT sensors .... could they be disconnected or is the Dynon itself having a problem ? The EGT readings were, by cylinder, 850, 905, -99 and 127. I guess the latter two are bad ? The CHT readings were all bad .... -70, 57, -70, 91. Or could this be a customization issue ? Oddly most of the customization parameters seem to have been reset. The green, yellow, red range settings are also out of whack. I doubt the mechanic would have done this unless he accidently hit some kind of "restore factory settings" switch. Is that possible ? Is there such a reset ? Even the tachometer was wrong .... it evidently showed 50% of the RPM. I did find a divisor setting which was set at 2.0. When I changed it to 1.0 the tach reading seemed right.

 

There are other display problems, including new items that I don't recognize. Even the fuel remaining can't be reset to "full" .... evidently the 34 gallon setting is missing. Some of the displays are different than before. There's even a bar for the outside air temperature which was never there before. Strange.

 

Any ideas what happened ????

[Roger Lee]

You still have a bad ground wire somewhere or you have a bad Dynon and that would need to be sent back, but my money still says it's a bad wire. I doubt it was a setting, but you could check under the GLOBAL setting and make sure it is set to Rotax and not something else. The weird and low power you have had lately may have caused the unit to go bad or corrupt the files. You could try an update and re-install the files.

[Steven]

Thanks, Roger.

 

I think it's safe to fly the plane even with some bad Dynon EMS readings, so my inclination is to fly it up to FDUSA headquarters, about an hour flight, and have them check it out. It might even be best if I had them do the annual 3 months early. Safety is my priority and maybe the plane should get a very thorough inspection along with a Dynon fix or lose wire remedy.

 

I'm skeptical that the local mechanics can resolve this since they have no prior experience with the CTLS.

[Roger Fane]

Steven,

 

As Roger Lee said, check to see if the D-120 is still set up for Rotax in the Setup menu. Seeing 4 each of EGT and CHT temps is not usual, as there are only 2 of each probes on the engine. Once you set it for Rotax, it will know which probes are in use, and how to calculate the correct readings. I think your power issues caused the stored settings to be reset.

[Steven]

Thanks Roger (both of you !) -

 

I was at the plane yesterday with the EMS installation guide which contains a detailed chapter on configuration and customization. As you both suggested, the first thing I did was check the global parameters for engine type. It was wrong ! Instead of ROTAX it had "OTHER" - when I changed it to ROTAX, the situation improved, but I still had lots of configuration left to do .... I specified the # of sensors as 2 rather than 4 and also made a correction to the sensor type. Thereafter the EGT and CHT displays appeared correct. CHT may have been a bit low but I was just idling, so I'll check it when I'm flying.

 

I then spent about 30 more minutes correcting other sensor related information. The manual was very helpful and had specific guidelines for the ROTAX 912.

 

At this point my EMS display is nearly back to normal. A few of the color ranges may not be quite right. I still have an odd message taking up nearly a third of the screen - "No HS34 found". I didn't have this message before and I don't think HS34 is in use, so there must be some global parameter still wrong, but I couldn't find it. I'll work on that further next time and may post a question on the DYNON forum about it.

 

Thanks again for all the help !

 

Steven

[Roger Lee]

The HSI message is in the toggle setup screen that determines which screen boots up first and then it's rotation. Go in there and change the rotation of the screens and the boot up screen you always want to come up first.

[Roger Fane]

The HS34 message refers to the Dynon HS34 Expansion Module. It allows you to connect additional items into the system, such as additional sensor, or a Nav Radio and GPS. Some CT's have them, some don't. If you don't have one, and you added anything to the GP sensor settings, you'll get an error. If you have one, and it isn't turned on, you will get an error. Also check the settings under the DSAB menu, to make sure yours is configured correctly.