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More Tri-Pacer Generator Info

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jnmeade

Joined: 27 Sep 2012
Posts: 12

Posted: Sat Dec 21, 2019 4:59 am Post subject: More Tri-Pacer Generator Info

The generator is an Aerotechlou rebuilt and installed in 2014.  It is  

almost certainly a Delco Remy 35 amp and I'm assuming it is a type "A"  

circuit as described in their literature.  We're trying to run down the  

paperwork.  There is a vision port which can be viewed and from that the  

brushes look well seated and the commutator is clean and serviceable.  The  

VR is a Zentronic G1350 which looks to be of modern design (no mechanical  

points).  Troubleshooting on the Aerotechlou site says remove the field  

wire and jumper the field terminal to aircraft ground.  Remove the  

armature wire and measure the voltage to ground with a DC voltmeter and  

the engine running.  The voltage should follow engine RPM.



I'm going to do this by taking the wires off of the voltage regulator,  

which is on the firewall, instead of the governor.  The governor is  

virtually inaccessible.  To get at it one must pull the prop and the front  

cowl.  Not inclined to do that until it's the only choice.  I understand  

this does not isolate the wires, but if the wires are the problem the prop  

and cowl have to come off anyway or get someone with smaller fingers.

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat Dec 21, 2019 9:20 am Post subject: More Tri-Pacer Generator Info

At 06:56 AM 12/21/2019, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "James Meade" <jnmeade(at)southslope.net>



 The generator is an Aerotechlou rebuilt and installed in 2014.  It is  

 almost certainly a Delco Remy 35 amp and I'm assuming it is a type "A"  

 circuit as described in their literature.  We're trying to run down the  

 paperwork.  There is a vision port which can be viewed and from that the  

 brushes look well seated and the commutator is clean and serviceable.  The  

 VR is a Zentronic G1350 which looks to be of modern design (no mechanical  

 points). 	


   EXCELLENT!  An updated system . . . nice that your

   vintage bird can stay as close to original as

   possible/practical.



  	  Quote: 	
		    Troubleshooting on the Aerotechlou site says remove the field  

 wire and jumper the field terminal to aircraft ground.  Remove the  

 armature wire and measure the voltage to ground with a DC voltmeter and  

 the engine running.  The voltage should follow engine RPM. 	


   An excellent data point . . . but this only says

   the brushes are 'mostly' in good contact. Since

   system charging currents flow in the brushes,

   a voltmeter falls way short of duplicating

   a 'proof load'.  When you do this test, add

   at least one, if not 2, 55 Watt head lamps to

   the load. Adding this load makes flaky brushes

   more likely to demonstrate their problems.



   And this test isn't a sure bet . . . you've described

   situations where the system DID produce adequate power

   for significant periods of time . . .



 

  	  Quote: 	
		  I'm going to do this by taking the wires off of the voltage regulator,  

 which is on the firewall, instead of the governor.  The governor is  

 virtually inaccessible. 	


   Good idea.



  	  Quote: 	
		    To get at it one must pull the prop and the front  

 cowl.  Not inclined to do that until it's the only choice.  I understand  

 this does not isolate the wires, but if the wires are the problem the prop  

 and cowl have to come off anyway or get someone with smaller fingers. 	




 

   Sounds like your on a promising track to discovering

   root cause. Run the traps on the manufacturer's

   recommended troubleshooting procedures. If no

   joy, get back here and we can offer further advise

   on how to track down the problem.



   Do you put a lot of hours on this a/c? That generator, under

   moderate loads should have a brush life on the order

   of 200-300 hours . . . maybe better. But your inspection

   window should confirm/deny brush wear as the problem.



   The symptoms you describe DO suggest that it's

   a brush problem. If the VR is solid state, then

   probability of failure is low . . . probability

   of intermittent failure lower still . . . but

   not zero in any case.



   Keep us appraised of your progress . . . we don't

   often get to witness the detective work on

   vintage problems!



 

   Bob . . .

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jnmeade

Joined: 27 Sep 2012
Posts: 12

Posted: Sun Dec 29, 2019 8:10 pm Post subject: Re: More Tri-Pacer Generator Info

The problem is a 25A circuit breaker that seems to have  become intermittent.  I say that based on it having "reset" itself at least once.

Removed field wire and jumpered it to ground.  Removed armature wire and put a DC voltmeter in series with it to ground.  At idle the voltage was about 6 VDC.  At 1500 RPM the voltage was 28VDC.  This seems to prove the generator is producing current.  All electronics were off and we only ran this test for a couple of seconds.

Reinstalled the voltage regulator and observed that the green VR light was off at low RPM and the GO red light was on because generator voltage was below battery voltage.  Advancing RPM the green VR goes on and the red GO light goes off.  Seems like the VR is OK.

Why does ammeter show discharge when charging system tests good?

Started fiddling with generator circuit breaker (probably original in 1955 airplane) and found it would engage and the ammeter showed an appropriate charge and response to RPM and load changes.

For now, I'll treat it as a transient and watch it, but if it recurs the circuit breaker will need to be changed out.

Thanks for the tips and encouragement.

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skywagon185(at)gmail.com
Guest

Posted: Sun Dec 29, 2019 9:32 pm Post subject: More Tri-Pacer Generator Info

I have seen CB's, especially old ones, do some strange behavior; like stuck open after reset, permanently stuck closed.

You maybe on to the problem about needing to change out the CB....



On Sun, Dec 29, 2019 at 8:16 PM jnmeade <jnmeade(at)southslope.net (jnmeade(at)southslope.net)> wrote:



 	  Quote: 	
		  --> AeroElectric-List message posted by: "jnmeade" <jnmeade(at)southslope.net (jnmeade(at)southslope.net)>

 

 The problem is a 25A circuit breaker that seems to have  become intermittent.  I say that based on it having "reset" itself at least once.

 Removed field wire and jumpered it to ground.  Removed armature wire and put a DC voltmeter in series with it to ground.  At idle the voltage was about 6 VDC.  At 1500 RPM the voltage was 28VDC.  This seems to prove the generator is producing current.  All electronics were off and we only ran this test for a couple of seconds.

 Reinstalled the voltage regulator and observed that the green VR light was off at low RPM and the GO red light was on because generator voltage was below battery voltage.  Advancing RPM the green VR goes on and the red GO light goes off.  Seems like the VR is OK.

 Why does ammeter show discharge when charging system tests good?

 Started fiddling with generator circuit breaker (probably original in 1955 airplane) and found it would engage and the ammeter showed an appropriate charge and response to RPM and load changes.

 For now, I'll treat it as a transient and watch it, but if it recurs the circuit breaker will need to be changed out.

 Thanks for the tips and encouragement.

 

 

 

 

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