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  #1  
Old 06-09-2019, 06:41 PM
rv7guy2 rv7guy2 is offline
 
Join Date: Apr 2005
Posts: 70
Default Alternator issue?????

Hello there.
I was up for a “ tour of the neighbourhood” last week when I noticed a reading on the Skyview Engine monitor that didn’t look right to me. I am wondering if I may have the beginnings of an alternator failure or another pending problem? I was motoring along at 3500 feet and 75% power when I noticed my voltage was showing 13.9 volts while the alternator/amperage reading was 1 amp. Normal readings are 14.3 volts and 2 amps. I shut off the Alternator switch for about 10 seconds with the resultant “low voltage” alarm in my ear from the Skyview EMS. I turned the alternator switch back on and the amps stayed at 1 while the voltage went to 14.0 and then dropped to 13.9 and stayed there. A few weeks ago I had a hard start and the 60 amp alternator breaker popped and refused to stay in so I aborted the flight and went back to the hangar and let things cool down. After 1/2 hr I started up again and the breaker stayed in while the amp reading came down as the battery recharged.
I changed the Odessy battery for a new one last fall and as per normal here in SW Ontario I took it out of the plane and stored it in the warm dry basement for the winter.
The alternator is from Plane Power and up to last Thursday I never had this or any other electrical issue except for the popped breaker as noted above.
So, the question is again, am I in for an alternator failure or is my “”new” battery pooched?

Thanks for any comment
Dave C
RV 7
C-GCPD
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  #2  
Old 06-09-2019, 06:45 PM
RVDan RVDan is offline
 
Join Date: Jun 2012
Location: Frederick, MD
Posts: 636
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Somethings is up for sure. I do question your reference as the amps normally shows +2. But that depends on how you set up the shunt. The voltage should be stable assuming that the engine is turning fast enough so that the alternator can meet the load. So at what engine RPM were you doing this check. What alternator?
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  #3  
Old 06-09-2019, 08:21 PM
Jonathan Alvord Jonathan Alvord is offline
 
Join Date: Feb 2018
Location: Prosser, WA
Posts: 56
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I would check the rectifier diodes if you have any. Mine went out and an after replacing alternator (pull prop, replace belts...). Thought it was good and then everything when black. After checking everything ended up replacing a $5-10 part and haven't had a problem since.
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  #4  
Old 06-10-2019, 07:04 AM
pilotkms pilotkms is offline
 
Join Date: Mar 2007
Location: WARNER ROBINS, GA
Posts: 314
Default Fuses?

I had similar experience over Nowhere Texas. Reached my destination (CA) and worked with a knowledgeable electrician. Verified the battery, the alternator and Skyview were operating correctly. Pulled the 2 1Amp Shunt fuses and cleaned the contacts. Test flite was OK. Returned 1800 miles home with no issues.
Electrical guy surmized that the fuse connections were the most likely culprit as they carry MICRO amps to the Skyview to display the readings. 25 tach hours and So far so good.
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RV 7A RV #9700 May 2017
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  #5  
Old 06-10-2019, 08:35 AM
RVDan RVDan is offline
 
Join Date: Jun 2012
Location: Frederick, MD
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Quote:
Originally Posted by pilotkms View Post
I had similar experience over Nowhere Texas. Reached my destination (CA) and worked with a knowledgeable electrician. Verified the battery, the alternator and Skyview were operating correctly. Pulled the 2 1Amp Shunt fuses and cleaned the contacts. Test flite was OK. Returned 1800 miles home with no issues.
Electrical guy surmized that the fuse connections were the most likely culprit as they carry MICRO amps to the Skyview to display the readings. 25 tach hours and So far so good.
That could explain a low amps indication, but not the voltage variation, which is another input altogether.
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  #6  
Old 06-10-2019, 08:38 AM
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Raymo Raymo is offline
 
Join Date: Nov 2014
Location: Richmond Hill, GA (KLHW)
Posts: 2,019
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Do you have the ALT fail light/indicator hooked up? My PP failed while on approach a couple months ago. Sent it in to Hartzel and they sent back a new unit (under warranty). While waiting for the new unit, I opted to install a B&C alt with external regulator (as have many others here).
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  #7  
Old 06-11-2019, 11:24 AM
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gmcjetpilot gmcjetpilot is offline
 
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My pet issue is turning internally regulated alternators off and on again under load. I don't know the PP brand, but stock Nippon Denso alternators will often fail when you do that. That on off wire for stock alternators is wake up and go to sleep signal and not made to switch Amps while spinning under load.
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  #8  
Old 06-11-2019, 12:06 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,863
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George, you might be thinking about a true 'load dump', where the *load* (the B-lead) is disconnected while the alternator is attempting to drive a significant load. This is a real 'thing'; I've had it happen to me (stupid human trick; not the fault of the alternator). This is not the same thing as using the I terminal to control the internal regulator.

The 'I' ("ignition") terminal (control) acts in different ways on different older ND models. On most I've seen, the internal regulator is designed to keep the alternator 'off' until voltage is applied to the 'I' terminal (after engine start). On some of these, once voltage is applied to the I terminal, the alternator will continue to produce output even if voltage is removed from the I terminal. On others (ex: the model that Ross from SDS uses), the I terminal will truly control the alternator's output: voltage on I = output and no voltage on I = no output. (PLEASE note that this doesn't mean it has positive control; in most of these internal regulators, if the power transistor fails shorted the I terminal cannot control the regulator/alternator.)

Using the I terminal to control the alternator will not cause a 'load dump'; removing I terminal voltage tells the regulator to remove the alternator's field voltage, which means it cannot produce output.

BTW, I've seen the bizarre current readings due to poor (high resistance) connections in the shunt's protective fuses.

BTW #2, if you're using a 60A breaker and your alternator is rated at anywhere near 60A, nuisance trips are a possibility; a probability if you move the alternator status from off to on while there are significant loads and/or the battery is partially discharged.

BTW #3, 13.9V is marginal charge voltage for an SLA battery. I'd want to get that corrected, even if there's nothing 'wrong' with the alternator. But I'd suspect failed diode(s), as others have already mentioned.

Charlie
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  #9  
Old 06-11-2019, 08:08 PM
tkracmer tkracmer is offline
 
Join Date: Jun 2005
Location: Fort Myers, Florida
Posts: 9
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Check your engine to airframe ground carefully. I had similar symptoms and found the ground cable to be slightly loose in the terminal. I cleaned and soldered the cable end to the cable and have had no further problems.
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  #10  
Old 06-15-2019, 02:15 PM
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gmcjetpilot gmcjetpilot is offline
 
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Quote:
Originally Posted by rv7charlie View Post
George, you might be thinking about a true 'load dump', where the *load* (the B-lead) is disconnected while the alternator is attempting to drive a significant load. This is a real 'thing'; I've had it happen to me (stupid human trick; not the fault of the alternator). This is not the same thing as using the I terminal to control the internal regulator.
I know what you are saying, but I am not thinking the B-lead.

Quote:
The 'I' ("ignition") terminal (control) acts in different ways on different older ND models. On most I've seen, the internal regulator is designed to keep the alternator 'off' until voltage is applied to the 'I' terminal (after engine start). On some of these, once voltage is applied to the I terminal, the alternator will continue to produce output even if voltage is removed from the I terminal. On others (ex: the model that Ross from SDS uses), the I terminal will truly control the alternator's output: voltage on I = output and no voltage on I = no output. (PLEASE note that this doesn't mean it has positive control; in most of these internal regulators, if the power transistor fails the I terminal cannot control the regulator/alternator.)
I have heard of this 3 times. just anecdotal mind you, after cycling the (ALT) or "I" ignition switch off the alternator did indeed shut down except in one case. However when they put the ALT switch back on, "I"power, alternator failed immediately. In one case they claimed they got over voltage. Also fun fact not all ND's are original but clones from China. Some models long out of production and no cores to do crappy rebuilds on are new clones made in China. Who knows what is in the IR, rocks and dry wall dust. They are potted so you can't take them apart easily. However there are good quality replacement IR's and clone alternators. I bought two brand new genuine mini ND alternators intended for Kubota tractors... I am sure of the quality.


Quote:
Using the I terminal to control the alternator will not cause a 'load dump'; removing I terminal voltage tells the regulator to remove the alternator's field voltage, which means it cannot produce output.
I think you alluded to the "I" (lets assume I = ignition) does not directly control the FIELD. Power to the IR (internal voltage regulator) comes from the B-lead. So we agree it is just a signal line ON or OFF... When you turn the ignition on, the "I" pulls down a transistor and powers the IR. The alternator is not spinning at this point or just starts spinning as you crank. Many IR's have soft start and will ramp up the field. OK. However when you are at full RPM, have a high load and cycle the "I" switch OFF and back ON it overloads that transistor (my theory). So you get nothing or get erratic operations including OV.

In a car when you turn the car ignition off, this kills the "I" and IR, but then alternator also stops spinning. If you could leave "I" (12 volts) and the B-wire is still on the battery hot, parked, you get parasitic drain as the IR is being powered trying to excite the field. So it is the go to sleep signal. In theory if you wired the "I" to the B lead it would be a "One Wire" alternator. You really don't need the "I" if the battery switch kills the Alternator B lead to the battery. However it is good to wire the "I", but I suggest you have it so when BAT is off the "I" is off. Bat is on "I" is on. I use a double poll single throw switch for battery alternator. together. If I want to KILL the "I" a pull-able CB will do the trick. As mentioned below I have the B-lead to it's own pull-able CB.

You can just wire the "I" to the B-lead in theory but I would not. In fact some brands of alternators (for racing) are ONE WIRE. B-lead only.

Quote:
BTW, I've seen the bizarre current readings due to poor (high resistance) connections in the shunt's protective fuses.

BTW #2, if you're using a 60A breaker and your alternator is rated at anywhere near 60A, nuisance trips are a possibility; a probability if you move the alternator status from off to on while there are significant loads and/or the battery is partially discharged.

BTW #3, 13.9V is marginal charge voltage for an SLA battery. I'd want to get that corrected, even if there's nothing 'wrong' with the alternator. But I'd suspect failed diode(s), as others have already mentioned.

Charlie
Those are all awesome tips. Thank you.

The big argument is IR alternators are bad and inferior to external VR alternators, because you can't control them and they could have an OVER VOLTAGE.... It is unlikely. I know of only one claimed OV and the guy cycled the "I" power in flight under load. The "I" is for sleep when you turn the car off and waking it up before you start. It is not intended to control the alternator under load. However the way I handled my IR OV concern is a 50 amp CB on the B - lead for my 40 amp ND alternator. I can pull the CB if needed. However the avionics buss has dual OV relays in parallel. I could put a massive CROW BAR on the 50 Amp CB, however I'm not that worried about OV. Also most avionics today work up to +30 volts with their own internal regulation. Some say you don't need an avionics master and can start with avionics on... To each his own. I rather have avionics and EFIS off for start.

How many cars have alternators go OV? Never heard of it. Again not scientific but it's not a runaway problem (Pun intended). Computers and electronics in cars need more protection than ever. However today cars alternators are computer controlled by ECU. My VW voltage varies, so it does not cook the battery or waste fuel by making more power than needed. Marine alternator and regulators do that as well... Dumb airplane alternators and regulators (internal or external) are fixed voltage still.

Some insist on external VR like a religion. I do see an advantage in that the VR is not as hot or being vibrated. However the rectifier is more likely to go, and that has to be on-board the alternator (unless you want to run a bunch of 3 phase wires).

You can modify your IR alternator and get an external VR. Transpo V1200 is one I recommend. It has adjustable voltage with OV protection. If you want state of art marine battery gear, alternators, regulators are sophisticated. However they tend to be a bit big, heavy and bulky.
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Last edited by gmcjetpilot : 06-16-2019 at 06:36 PM.
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