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Rotax 912ULS regulator failures

A

Aircore

I'm New Here
I'd be happy to offer some input. Keep in mind I have not read this entire thread on this matter. The regulator is a good part. We have thousands and thousands of hours on them without failures.
First, the rotax manual clearly states that if the R-B regulator terminals are hot and C is open, permanent damage may result. I have ran into 2 failures do to 12v failure to the C terminal. I have contacted Vans and am awaiting for a reply from their engineering to track down the system failure as I am not able to track the exact path through their box via the online schematic. From what I have discovered is that avionics switch controls the 12v input to the regulator C terminal. IMO, this would be a bad thing do to. As it offers the pilot the opportunity to isolate this input resulting regulator damage. As a authorized Rotax repair center. And have done dozens of firewall forward 912ULS designs and installations. My solution until Vans engineering offers one. Is to take the regulator C terminal to the normally open side of the master relay for its 12V source. This offers a better solution then parallel R-B-C as per the Rotax manual, because this isolates the regulator from the battery when master is off. Which will result in a slow battery bleed from the diodes in the regulator. I have done this on 2 RV12's with 100% success. I hope this helps some. I will follow up when I hear back from Vans engineering.
Scott
 
Fantastic Repair

I can confirm the repair works and is relatively easy to do...it was especially easy since Scott at Aircor did the fix...he did it quickly and efficiently..and charged very fairly....can't say enough good things about these two guys at Aircor Aviation...Dick
 
Scott,

I spent some time going through the D-180 schematic, since that's the setup I have and I got curious about it. After half an hour of squinting and head scratching I had to conclude that the schematic was simply incorrect, as there was no sign of anything actually feeding the VREG input.

So, I downloaded the newest Skyview electrical system diagram. That one is more believable. It shows the VREG C terminal fed through one side of the master switch, and the source is a fused wire getting battery voltage from the AV-50001 module (check the P-12 sector of the "Skyview-after-08-25-11" diagram for the VREG circuit). There's a 1A fuse that is not named on the diagram - I don't know if it's on the AV-50001 PCB and not accessible form the panel or what.

If I were designing it, that's almost how I would do it if the regulator were behind the firewall. I'd use the switched side of the master relay if the regulator was on the forward side of the firewall, with an in-line fuse or fusible link. The way it's set up now you're ALMOST guaranteed to have the VREG input hot before engine start. There is a failure mode that would result in a hot alternator and no VREG input. If the 30A alternator fuse is OK but the 1A fuse for the regulator is blown, you'll have AC input and no sense input. The same could happen if one side of the master switch were defective.

So... if you had to run a wire from the master to the regulator, I would say that 1.) you have not fixed the problem, but worked around it; there's probably a blown fuse in the AV-50001 module. 2.) I hope you used a fuse or fusible link to prevent a failed regulator from either catching or causing a fire or creating a lot of smoke.

I went back and looked at the D180 diagram again, having found the answers for the Skyview panel. There's a missing segment of VOLTAGE REG wire on the D180 diagram. Unless there's a missing fuse in there too, there's an unfused wire carrying battery power to the master switch... not a huge deal, but personally I'd rather see it fused.
 
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As stated, yes it was a work around to Vans until I can get an answer. But a correct one per manufacture as stated by the Rotax manual and a method I have used dozens of times before. Positive side of master (relay) was used, not the master switch. If you know where a fuse is in relation to the AV. I'd sure like to know?? otherwise we are still just waiting an answer and for a valid legible schematic to land out per engineered.
 
Fixed

Carl; yes it is fixed, as opposed to flying to Arlington without radio because of to little voltage..on way home I had wing tip strobes, auto pilot, radio etc..and still charging on panel... Scott fixed it very quickly without a lot of fanfair..and considering I have been struggling with this for over a week it was monumental to get it fixed...if in future Van's engineers find a better or different fix we will address that then...thanks Scott
 
Aircor, Scott,
Welcome to Van's Airforce. There is a lot of information available here. You will find hundreds of posts relating to the Rotax regulator.

Your experience with the Rotax regulator is vastly different from ours. I hear your point of view from a lot of IRMT's and I don't understand the disconnect between your experience and ours. This regulator is the weakest link in the RV-12. And the failures have nothing to do with Van's application.

The van's wiring diagram may be hard to follow, but almost everything you need is there. Van's intention is for the builder to generate a custom drawing based on the hardware version(s) and options installed in that aircraft. You need to choose the correct layers in Autocad. This is the builders job, not Van's.

I believe the warning you quoted, along with the temperature restrictions in the Rotax manuals are an excuse to blame the regulators failures on the aircraft manufacturer and owner/operators. I base this on the principle of the regular. This regulator uses a switched rectifier bridge to turn the output power on/off. When the sense input (C pin) is satisfied, the SCR gate power is disabled, this is equivalent to removing the 12 volts from the C input. If the Rotax statement were true, every time the regular was satisfied there is a chance it would blow the regulator.
The power components Ducati choose are rated for 800-1000 volts, more than adequate for this 50 volt circuit. I have yet to examine any regulator with any electricity failed component, all failures are related to component application, assembly and/or fabrication.
 
Aircore said:
As stated, yes it was a work around to Vans until I can get an answer. But a correct one per manufacture as stated by the Rotax manual and a method I have used dozens of times before. Positive side of master (relay) was used, not the master switch. If you know where a fuse is in relation to the AV. I'd sure like to know?? otherwise we are still just waiting an answer and for a valid legible schematic to land out per engineered.
Click to expand...
Oh, I certainly wasn't suggesting that the solution is not a valid one (though I'd still want to see a some sort of protection on the wire). Kudos for getting him flying, good show. I just said that it was a workaround in this instance, not a permanent fix. You've bypassed the manufacturer's (Van's) solution without finding the root cause. Nothing wrong with that as a temporary measure until the root cause can be found and fixed.

The Van's download page has PDFs for both the Skyview and G3X flavors of panels; both are legible (unlike parts of the D180 diagram). I believe the DWG files are probably even better, though my freebie DWG viewer quit working and I haven't bothered to find another. I know when I was using the D180 DWG file it was perfectly readable, albeit a little tedious to scroll through. One of these days I should make good on my threats to get a large format printer; some of the really nice older HPs are dirt cheap. But I digress.

  • Battery voltage is taken from the master relay to AV-50001 switch & fuse module through the shunt.
  • On the AV-50001 switch & fuse module there's a 30A ALTERNATOR fuse that feeds the GEN circuit, back to the B+ and R terminals of the regulator.
  • From the fused GEN circuit there's a line to an un-labeled 1A fuse; that feeds the VREG circuit. This is the fuse that I suspect is on the PCB -- since it's not labeled on the schematic, and there is no panel mounted fuse for it.
  • The VREG circuit is switched by the master switch and connects to the C terminal of the regulator.

The POH also shows the VREG (C) feed from the master switch, although it doesn't show the 1A fuse. The diagram shows two more for the shunt sense feeds (AMPS A and AMPS B). Mine is a completely different setup, but I'd love to see the guts of that module... I'd bet a nickel there are three glass fuses soldered to or clip mounted to the PCB in it.

So why bother tracking down the root cause if the workaround works? This is just my opinion, but something is busted, and it's an airplane, and I wouldn't want to keep flying indefinitely with busted stuff... even if you've worked around the busted stuff. I'd give it a 99% chance it's just a popped fuse on the module board, but that other 1% covers a lot fo things that could just ruin your whole day.

But, it's not a spam can so you're free to leave it that way as long as your personal comfort level dictates. :)
 
DaleB said:
  • Battery voltage is taken from the master relay to AV-50001 switch & fuse module through the shunt.
  • On the AV-50001 switch & fuse module there's a 30A ALTERNATOR fuse that feeds the GEN circuit, back to the B+ and R terminals of the regulator.
  • From the fused GEN circuit there's a line to an un-labeled 1A fuse; that feeds the VREG circuit. This is the fuse that I suspect is on the PCB -- since it's not labeled on the schematic, and there is no panel mounted fuse for it.
  • The VREG circuit is switched by the master switch and connects to the C terminal of the regulator.

The POH also shows the VREG (C) feed from the master switch, although it doesn't show the 1A fuse. The diagram shows two more for the shunt sense feeds (AMPS A and AMPS B). Mine is a completely different setup, but I'd love to see the guts of that module... I'd bet a nickel there are three glass fuses soldered to or clip mounted to the PCB in it.
Click to expand...

The three fuses are indeed solder in fuses on one of the AV-50001 pcbs (though they are not glass)
 
Judging by the fact that the master switch light works, I do not think the 1 amp fuse is blown in olderthandirt' plane. If the master switch light goes out after pulling the 30 amp fuse, that will confirm that the 1 amp fuse is good.
 
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Aircore said:
Keep in mind I have not read this entire thread on this matter. The regulator is a good part.
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Well you should read all the threads then. Sorry to strongly disagree with you but these regulators are failing too often to be a "good part". Maybe you will get the info from Van's that allows us to finally solve the problem with why these are burning up. Glad to have you onboard the good ship VAF. Thank you for any help you can provide towards finding a solution.

As an update to my situation, my $70 tractor regulator is going strong 120 hours now mounted in the same original location.
 
Mich48041 said:
Judging by the fact that the master switch light works, I do not think the 1 amp fuse is blown in olderthandirt' plane. If the master switch light goes out after pulling the 30 amp fuse, that will confirm that the 1 amp fuse is good.
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Yeah, good point -- I see that the LED is powered from the VREG signal. That, then, would seem to indicate that it's downstream from there. Nothing left but the master switch, two cables and a PCB trace in the AV-50000A module, so it's just good old fashioned meter work to find it.
 
You are correct Dale, the problem could have been easily pinpointed and repaired the right way instead of bypassing the master switch and creating a new hazard.
 
Mich48041 said:
You are correct Dale, the problem could have been easily pinpointed and repaired the right way instead of bypassing the master switch and creating a new hazard.
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Oh, I wouldn't be too hard on him. It's a temporary fix; there's really nothing technically wrong with the fix itself and I'd rate the hazard factor fairly low as a temporary thing. If he used light enough gauge wire (like 24 AWG) it will act as a fusible link anyway.

I just wouldn't want to leave it that way permanently. There's something not right. It could just be a D-sub pin pushed in, no big deal and it will probably never cause any more problems. It would also only take a few minutes to fix, once found. On the other hand, it could be an indication of something more severe that isn't obvious yet. There could be a cracked PCB, pinched harness, etc. Until the root cause is found and fixed, I would be most worried about something as yet undiscovered going badly during flight or while away from home.
 
Thanks for your guys input, that is how we all learn. It is my understanding that the AV is just a pass through and is not required for the circuit. The correction that was made was safe and functional. I am an authorized service center for a half a dozen of major SLSA manufactures and a Rotax repair center. And have done full FWF RD with electrical for manufactures you would all know. With the same practices and procedures as previously stated. ELSA is a grand thing. :) So please be kind when suggesting hazards. I was just handed a legible set of schematics, when or if I can find the allusive 1amp circuit protection. I will certainly pass that info along to you guys. Have a fun flying holiday weekend. Be safe out there.

Scott
 
Scott

There was never a doubt the fix was safe...maybe it could be done differently but at least I had a charging system and now could fly using my radio since I had adequate power...if in future the elusive 1 amp fuse is found maybe I can return and we can do it differently, in the meantime I am flying and enjoying a airplane I built that I could not have been enjoying without your help..thanks Dick
 
f1rocket said:
Well you should read all the threads then. Sorry to strongly disagree with you but these regulators are failing too often to be a "good part". Maybe you will get the info from Van's that allows us to finally solve the problem with why these are burning up. Glad to have you onboard the good ship VAF. Thank you for any help you can provide towards finding a solution.

As an update to my situation, my $70 tractor regulator is going strong 120 hours now mounted in the same original location.
Click to expand...

Thanks for the welcome, and happy to learn and help. So the "good part" thing. I have over 80 aircraft in my data base that use this regulator. So that would be a accumulative of untold thousands of hours. Over the years I have replaced 4. 3 of them had loose spade terminals which with current we know generates heat resulting in a failure. I would bet you a condition inspection, that if the D connector pins were not used for the C circuit duties. And an affirmative ground was used directly from the regulator mounting (not the airframe) to the negative side of the battery. Failure rates would be almost nil. I'm happy that you found a solution that is solid ! Experimentals are great are they not ! :) Have a great weekend, and thanks again.
 
olderthandirt said:
There was never a doubt the fix was safe...maybe it could be done differently but at least I had a charging system and now could fly using my radio since I had adequate power...if in future the elusive 1 amp fuse is found maybe I can return and we can do it differently, in the meantime I am flying and enjoying a airplane I built that I could not have been enjoying without your help..thanks Dick
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You are very welcome ! You have a beautiful aircraft. Have a great holiday weekend and try to get some fuel burnt :)
 
Aircore said:
...I have replaced 4. 3 of them had loose spade terminals which with current we know generates heat resulting in a failure...
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Scott what you are seeing is the secondary failure, the primary failure was internal plate to diode separation, this is very common in the 965 347 and 965 345 version regulators.
 
olderthandirt said:
There was never a doubt the fix was safe...maybe it could be done differently but at least I had a charging system and now could fly using my radio since I had adequate power...if in future the elusive 1 amp fuse is found maybe I can return and we can do it differently, in the meantime I am flying and enjoying a airplane I built that I could not have been enjoying without your help..thanks Dick
Click to expand...

Dick,
The fuse is not elusive at all. I already posted that it is a PCB soldered in fuse mounted in the switch module, but that doesn't really matter because as Joe has already told you, if the light on the master switch illuminates it proves that the fuse is not blown.
 
MMiller said:
Scott what you are seeing is the secondary failure, the primary failure was internal plate to diode separation, this is very common in the 965 347 and 965 345 version regulators.
Click to expand...

Curious, how it was and by whom "specifically" determined that the spade was the secondary?
 
Scott,

I came to this conclusion. I looked at three regulators with melted connectors all had the internal failed to diode plate solder connection. It is also possible that operators of these units re-seated the connector looking for a bad connection while troubleshooting erratic operation, weakening the connection. but that doesn't matter, it's obvious that this internal failure did not happen after the "G" pin melted. Remember, this is a regulator, to compensate for the internal losses of a bad connection the unit will draw more input power.

Don't take my word for it, you have three failed regulators, check for yourself. I would like to know what you conclude. Or you can send them to me and I'll let you know what I find...but that won't be an independent review.

This failure mode does not apply to the 965 349 Rotax now supplies, they have there own separate issues.

Here is the case overview
scc5ts.jpg


Here is the failed plate connection, note the damage from arcing
kduxcp.jpg
 
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I just flew a couple hundred mile cross country today with my new Amazon knock-off regulator and cruised along at 14.4 volts. It does seem to operate a bit hotter to the touch than the Ducatti.
 
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