914 Inconsistent Charging

Jeff Blakeslee wrote:

The yellow wire to yellow wire reading is fine, but there should be infinite resistance between either yellow wire and engine ground.  In other words, NO continuity at all so NO reading on the meter.  Are you sure that the reading was not 14.5 Mega-ohms?  Some meters auto-scale and you won’t notice it switched to mega-ohms unless you are aware.

If that was a mega-ohm reading, then that might have been a false reading from current passing through your body by touching the test probe ends while doing the test.  If that was ohms or kilo-ohms then your Stator is shorted to ground and likely needs to be replaced.  Do the ground test again, noting the meter scale, and make sure not to touch the probe ends or bare wires with your fingers during the test.  Your body is a conductor.  

Here is a photo of a shorted stator we pulled out of a 912iS engine a few weeks back. This had similar test readings, the wire to wire test was in spec, but ground test failed.    I’ve not personally seen this on the 914 but I’m sure it can happen.  

I was so hopeful it is just the regulator based on the continuity that I ordered one from Lockwood.

Well, that black terminal is not good and I think the regulator and wire connectors should be replaced no matter how the alternator test comes out. So your new regulator won’t go to waste.  I’m hoping the grounded Stator wires was just a testing problem.

Your avionics and strobes have you at 8 amps, and in the pattern you will have both fuel pumps on so add 8 amps of engine load.  Your internal alternator won’t keep up with that 16 amp load until the engine is over 3500 RPM, so you may show some discharge in the pattern even with everything working properly.  Once you get any problems fixed, you might consider adding the optional (larger) belt driven alternator - which has its own built in regulator/rectifier.  You would need an LOA from BRM, but in my experience they have been good about that.  The US dealer can help your mechanic sort that project out.  

I've just seen your photo of the terminals on the regulator. They look burnt. This usually happens when either too much current has been drawn or there is a poor connection that has resulted in over heating.

You may be able to clean the terminals, but you don't want to scrape off any plating, failing that you will need to replace the regulator. It is highly likely that the mating half of the plug also suffers from the same problem. You can release the crimp terminals from the housing using a small flat-bladed screwdriver. If any of the crimp terminals are damaged then you can cut them off and replace them as necessary.

As Jeff has said, if you have a 16A load at low engine RPM then you will be overloading the built-in generator. I don't know how the system copes with such an overload, I don't have any experience of drawing so much current.

Jeff Blakeslee wrote:

Well, that black terminal is not good and I think the regulator and wire connectors should be replaced no matter how the alternator test comes out. So your new regulator won’t go to waste.  I’m hoping the grounded Stator wires was just a testing problem.

Your avionics and strobes have you at 8 amps, and in the pattern you will have both fuel pumps on so add 8 amps of engine load.  Your internal alternator won’t keep up with that 16 amp load until the engine is over 3500 RPM, so you may show some discharge in the pattern even with everything working properly.  Once you get any problems fixed, you might consider adding the optional (larger) belt driven alternator - which has its own built in regulator/rectifier.  You would need an LOA from BRM, but in my experience they have been good about that.  The US dealer can help your mechanic sort that project out.  

Fortunately i'm a 30 min flight from them in Lancaster, PA and Rich does most of my service.

Tested again it was on MegaOhms