Alternator Trouble

Any DA40 related topics

Moderators: Rick, Lance Murray

Post Reply
User avatar
vontresc
3 Diamonds Member
3 Diamonds Member
Posts: 85
Joined: Mon Mar 30, 2015 3:51 pm
First Name: Peter
Aircraft Type: DA40
Aircraft Registration: N569DS
Airports: KMSN
Has thanked: 1 time
Been thanked: 22 times

Alternator Trouble

Post by vontresc »

I am the maintenance officer for our flying club, and I've had nothing but issues with alternators this year. So far the Da40 has been good to me, but the last two flights the alternator kicked out early in the flight

https://www.flightdata.com/flights/N569DS/E4/2331576
https://www.flightdata.com/flights/N569DS/E4/2331580

I had the local shop look at it, but of course it won't replicate on the ground. I'll have them recheck the grounding wires after reading Arnaud's thread, but I am suspecting the voltage regulator. Before buying a new one is there anything else I ought to have them check? I just don't want to throw parts at this and hope for the best.

Thanks

Peter
User avatar
astaib
5 Diamonds Member
5 Diamonds Member
Posts: 616
Joined: Mon Feb 26, 2018 9:00 pm
First Name: Arnaud
Aircraft Type: DA40
Aircraft Registration: FGNJX
Airports: LFPX
Has thanked: 244 times
Been thanked: 51 times

Re: Alternator Trouble

Post by astaib »

Hi Peter,

You can send your voltage regulator to the manufacturer for bench inspection (Lamar).
I did that during my trouble.

If you need the contacts, ask me.

Arnaud.
Arnaud
DA40 Star 180 / 40.026 / 2001
Wingtip, landing and taxing LED (Whelen)
Skitube
GNS430 NON-WAAS
Steam gauges
Non certified ADS-b
User avatar
smoss
5 Diamonds Member
5 Diamonds Member
Posts: 742
Joined: Sun Dec 12, 2010 12:18 am
First Name: Steve
Aircraft Type: DA40
Airports: KVGT
Has thanked: 57 times
Been thanked: 134 times

Re: Alternator Trouble

Post by smoss »

It is also very easy to replace the brushes without removing the alternator. The kit was $92 from Aircraft Spruce about 7 years ago.
Steve
DA40 XL
User avatar
astaib
5 Diamonds Member
5 Diamonds Member
Posts: 616
Joined: Mon Feb 26, 2018 9:00 pm
First Name: Arnaud
Aircraft Type: DA40
Aircraft Registration: FGNJX
Airports: LFPX
Has thanked: 244 times
Been thanked: 51 times

Re: Alternator Trouble

Post by astaib »

I forgot to tell that the diodes can be also faulty but depending on which alternator you have, you can or you cannot change them.

There is a test to diagnose if the diodes are guilty: plug the accessory plug on the panel and mesure the tension in alternative current and in direct current. The direct current has to be similar to what the G1000 says and the alternative should be very small (less than 1,5 v). The best is if you have an oscilloscope to mesure the shape of the signal.

Arnaud.
Arnaud
DA40 Star 180 / 40.026 / 2001
Wingtip, landing and taxing LED (Whelen)
Skitube
GNS430 NON-WAAS
Steam gauges
Non certified ADS-b
User avatar
Rich
5 Diamonds Member
5 Diamonds Member
Posts: 4592
Joined: Mon Aug 30, 2010 12:40 pm
First Name: Rich
Aircraft Type: DA40
Aircraft Registration: N40XE
Airports: S39 Prineville OR
Has thanked: 145 times
Been thanked: 1180 times

Re: Alternator Trouble

Post by Rich »

Brushes are the component that are most inherently wear-out items. They are pressed against their respective rings with springs. The brush material wears over time and the springs slowly become weakened by heat. This can produce an intermittent problem until finally they quit working. The brushes and the various connections can be inspected visually. How old in Hobbs/Tach hours do you think the brushes are? I've been sitting on the replacement brushes for mine for a number of years. I know some here have reported needing brush replacement around 1200 tach hours. Mine is at 1324, but I'm reluctant to change something that's working. When I travel I do carry those spare brushes with me.

The one additional thing I wanted to look at in your posted data was amps, but that's not plotted. I will say that the ability to go through these graphs is something I wish I had available for my plane :(
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
User avatar
vontresc
3 Diamonds Member
3 Diamonds Member
Posts: 85
Joined: Mon Mar 30, 2015 3:51 pm
First Name: Peter
Aircraft Type: DA40
Aircraft Registration: N569DS
Airports: KMSN
Has thanked: 1 time
Been thanked: 22 times

Re: Alternator Trouble

Post by vontresc »

It's a relatively newish alternator 550 hours or so. VR is original to the airframe at about 3500 hours. I am just reluctant to throw $900 at parts and hope it fixes it.
User avatar
smoss
5 Diamonds Member
5 Diamonds Member
Posts: 742
Joined: Sun Dec 12, 2010 12:18 am
First Name: Steve
Aircraft Type: DA40
Airports: KVGT
Has thanked: 57 times
Been thanked: 134 times

Re: Alternator Trouble

Post by smoss »

Peter, the brushes can be easily inspected by just removing 2 screws and pulling out the little assembly from the back of the alternator. If you look at the part on Spruce, you'll see what you're dealing with. https://www.aircraftspruce.com/catalog/ ... -13833.php
If there's no carbon left on the sticks, that's probably the issue.
Steve
DA40 XL
User avatar
vontresc
3 Diamonds Member
3 Diamonds Member
Posts: 85
Joined: Mon Mar 30, 2015 3:51 pm
First Name: Peter
Aircraft Type: DA40
Aircraft Registration: N569DS
Airports: KMSN
Has thanked: 1 time
Been thanked: 22 times

Re: Alternator Trouble

Post by vontresc »

Well taking it to a competent mechanic helped. Turns out it was some bad grounds.
C5405F7F-1281-4FAF-806E-DA3EE34BC4AC.jpeg
I am quite pissed at the local shop on the field that claimed they checked the wiring. So we wasted $800 on a new voltage reg we didn't need after all.
Post Reply