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Thread: Interav Overvoltage

  1. #1
    Join Date
    Feb 2018
    Location
    Lacombe Ab, Canada
    Posts
    8

    Default Interav Overvoltage

    Good Morning,
    I'm working with an AME (A&P) on this, but we're both getting stumped... Interav alternator, worked fine before engine rebuild - and now has a massive overvoltage. Enough to fry every electrical component in the plane (the nav lights smelled awful). We replaced the over voltage regulator (Interav) with a Plane power O/V regulator and fired it up yesterday - tripped the c/b at 17.5v - (confirmed with Dynon and separate meter checking in ciggy lighter).

    We dbl checked the Plane Power O/V reg to make sure it was set to 12 - NOT 24 v - was good. Turned down the regulator 1/4 turn tried again. Continued this process until the regulator was turned down all the way - according to instructions this is backwards - turn the screw in to adjust voltage down - and it still tripped the breaker at 17.5v.

    We now suspect the alternator is the culprit - but I don't want to spend another bundle of cash without confirming.
    My thought is a pulley got mixed up on install and the alternator is spinning too fast. AME says no way, but how can we confirm this?

    Is there something in the alternator that would cause it to not 'listen' to signal from the O/V reg and stop producing power?

    We have checked and double checked all the brand new wiring - its hooked up right and the connections are new - no corrosion. We have double checked our meters and are convinced they work as the Plane Power O/V reg trips out right where its supposed to.

    I'm perplexed and going broke.... Any help would be appreciated!
    Thanks!
    Jim

  2. #2
    Join Date
    Dec 2015
    Location
    Lexington
    Posts
    16

    Default

    OM?
    If you havent picked up the Denso 100211-1680 alternator yet they're $120. brand new herehttps://www.densoproducts.com/Quickw...spx?zpid=41542

    Another supplier,
    http://powerstartoem.com/021080-0760...o-100211-1680/

    The custom bracket kit to mount it that Niagara Air Parts sold a few years ago with their Denso alternator kit is still available from them for $75. http://www.niagaraairparts.com/

  3. #3
    Join Date
    Oct 2005
    Location
    Graham, Texas
    Posts
    865

    Default

    Here is a lot of information to help you fix what you have.
    http://www.shortwingpipers.org/forum...rAv-Alternator

  4. #4
    Join Date
    Feb 2018
    Location
    Lacombe Ab, Canada
    Posts
    8

    Default

    Hi Rin - thanks for the reply. I'm concerned about using an auto alternator for the reason stated above- how do I know if I'm spinning the alternator at the right RPM. Have heard horror stories about folks having the exact same problems I am. I also checked the Niagra air parts site and they don't seem to have an alternator bracket - but look pretty handy for other things!
    Do you have any ideas how to check RPM of the alternator existing?
    thanks again
    Jim

  5. #5
    Join Date
    Feb 2018
    Location
    Lacombe Ab, Canada
    Posts
    8

    Default

    Thanks Steve - I printed off the manuals and trouble shooting - will bring them to town today and see if we can chase out any gremlins.

  6. #6
    Join Date
    Dec 2015
    Location
    Lexington
    Posts
    16

    Default

    Have a Denso linked above, purs out a constant 14.2 volts all the time. Are you Owner Maintenance?

    The Denso is a fine unit, been used on aircraft for 15 years, hundreds installed on aircraft and working fine. The speed the alternator is turning is not going to affect the voltage, it will affect the amperage. If the voltage is increasing with speed of the alternator I would suspect the voltage regulator.

  7. #7
    Join Date
    Nov 2006
    Location
    Mason, Ohio
    Posts
    307

    Default

    Jim,

    Figuring the RPM of the alternator is as simple as the ratio of the pitch diameters of the pulleys on the engine and the alternator. If you assume you cruise at 2400 RPM and the pitch diameter of the pulley on the engine is 7 in. and the pitch diameter of the pulley on the alternator is 3.625", the alternator is turning at 4634 RPM. A 40 amp B&C alternator is putting out about 32 amps at that RPM.

    Tom Anderson

  8. #8
    Join Date
    Feb 2018
    Location
    Lacombe Ab, Canada
    Posts
    8

    Default

    Tom-
    thanks for the input re RPM. what’s the formula for that? You make it sound far too simple.
    We took the interav alternator to a local shop where he looked at it briefly and tossed it in the recycle bin.
    Bought a new Plane Power alt to go with the voltage Reg and voila! Problem solved (for a heck of a lot of $$ mind you)
    thanks all for your input. I have out about zap hours on the plane since we got voltage figured out and all works well - 14.1 v fairly constant!

    again —- thank you!

  9. #9
    Join Date
    Nov 2006
    Location
    Mason, Ohio
    Posts
    307

    Default

    Jim,
    It's rea simple. If ARPM = Alternator RPM, ERPM = Engine RPM, Alternator Pulley Diameter = D1 and Engine Pulley Diameter = D2, then:

    ARPM = ERPM x D2/D1. The output amperage came from a chart of RPM vs output amperage that I received from B&C when I put one on my plane.

    Glad it worked out for you with Plane Power. I assume you moved the oil cooler to the baffling behind the #4 cylinder. If my recollection is correct, Plane Power's STC requires it. An alternative may be to use flexible oil cooler lines, but that's a modification of the STC.

    Tom

  10. #10
    Join Date
    Oct 2005
    Location
    Graham, Texas
    Posts
    865

    Default

    Quote Originally Posted by Tom Anderson View Post
    Glad it worked out for you with Plane Power. I assume you moved the oil cooler to the baffling behind the #4 cylinder. If my recollection is correct, Plane Power's STC requires it. An alternative may be to use flexible oil cooler lines, but that's a modification of the STC.

    Tom
    I spoke to Plane Power about this. It was not required by the STC but the installation per their STC didn't cover any modification to the oil cooler or brackets. I do those with a logbook entry.

  11. #11
    Join Date
    Nov 2006
    Location
    Mason, Ohio
    Posts
    307

    Default

    Steve,

    Thanks for responding. If you check out the AML list for STC SA10862SC http://rgl.faa.gov/Regulatory_and_Gu...ight=sa10682sc, you will see that for PA-18s, PA-20s and PA-22s it says "When modified with FAA approved rear mounted oil cooler". I am not surprised that Plane Power and now Hartzell don't realize this. A few years back before Hartzell while at Oshkosh I asked Plane Power about it and they finally after much head scratching said to use the STC for the rear mounted oil cooler available from the Stewarts. I am sure there are other ways around it, but this is what their paper works says. This is why they don't give instructions for modifying the oil cooler brackets.

    Tom

  12. #12
    Join Date
    Oct 2005
    Location
    Graham, Texas
    Posts
    865

    Default

    I have never seen anything official (within their STC) that the oil cooler had to be mounted on the rear baffle just a note on their website. They just had no data for modifying the oil cooler bracket so they put that note on their website. I had the discussion with the owner. I use to go over to Granbury and visit with them. I like the B&C alternator myself. Hopefully it will be STC'd by Oshkosh.

  13. #13
    Join Date
    Oct 2005
    Location
    Graham, Texas
    Posts
    865

    Default

    Quote Originally Posted by Tom Anderson View Post
    Steve,

    Thanks for responding. If you check out the AML list for STC SA10862SC http://rgl.faa.gov/Regulatory_and_Gu...ight=sa10682sc, you will see that for PA-18s, PA-20s and PA-22s it says "When modified with FAA approved rear mounted oil cooler". I am not surprised that Plane Power and now Hartzell don't realize this. A few years back before Hartzell while at Oshkosh I asked Plane Power about it and they finally after much head scratching said to use the STC for the rear mounted oil cooler available from the Stewarts. I am sure there are other ways around it, but this is what their paper works says. This is why they don't give instructions for modifying the oil cooler brackets.

    Tom
    Tom, I don't see anything in that AML that says you must have a rear mounted oil cooler. I see on their website where it says that but no where is the STC can I find the requirement of the rear mounted oil cooler which was my conversation with Rich at Plane Power/SkyTec when they were owned by Rich and his Dad and based in Granbury, Texas. I tried to upload the STC document but the file is to large to be uploaded to the website. Here is a link. http://planepower.aero/wp-content/up...14-0000-PP.pdf Curious if you found something I missed.

  14. #14
    Join Date
    Nov 2006
    Location
    Mason, Ohio
    Posts
    307

    Default

    Steve,

    I have attached the AML and highlighted where it indicates the oil cooler location must be modified. I took this off the FAA web site for STCs where it shows the compete AML.

    I agree with you about the B&C. I put mine on in 2006 with a field approval and it has been trouble free.

    Tom
    Attached Files Attached Files

  15. #15
    Join Date
    Oct 2005
    Location
    Graham, Texas
    Posts
    865

    Default

    Quote Originally Posted by Tom Anderson View Post
    Steve,

    I have attached the AML and highlighted where it indicates the oil cooler location must be modified. I took this off the FAA web site for STCs where it shows the compete AML.

    I agree with you about the B&C. I put mine on in 2006 with a field approval and it has been trouble free.

    Tom
    Yep, don't know how I missed that. They screwed themselves with that statement. Too bad, it is not that hard to modify the oil cooler bracket.

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