A while back my alternator decided to start cycling on and off every
now and again, mostly when under load.  It will never do it during a
day flight, and only during the day when running strobes.  I can
induce it at night fairly easily sometimes with the navs, fuel pump,
landing light, and panel lights (no strobes needed..they seem able to
induce the problem by themselves).  I was returning from Miss. a few
nights ago and it decided to do this.  I shut down the strobes and
everything was fine (as usual).  I turned the strobes back on and the
last 30 min or so of the flight was uneventful.

I installed a new B&C battery yesterday and the problem occurred
again yesterday evening 1 time near the beginning of the flight, and
more so on the ground after I landed and had the engine at idle
power.  I stayed in the pattern since I had a "known" electrical issue.

Here are  few things I may have forgotten to mention, and I can't be
sure if this could be a cause of my problem.

1)  A while back I noticed my main relay would not power the
panel.  I could hear the "clunk" when the masters were engaged, but
nothing on the panel.  After a few more tries, the     panel engaged
power and no problem.  I put the plane in the shop and they could not
duplicate the problem.  I had forgotten about this, as it has not
happened for a while now     later, it powered on).  Could this be the
root of my problem?

2)  I notice both my EI voltmeter as well as the Dynon (backup to my
gyro ;) )  are reporting about 13.5V when in flight.  I would assume
this should be around 14.5 or so.

3)  The main problem is that if under load, the system will "shut
down" the charging system intermittently and then come back
online.  Sometimes in a rapid (5 secs or so) succession     or sometimes
in more erratic unpredictable intervals. Like the flight back the
other night, it acted up then stayed online for the remainder of the flight.

    I thought I had the alternator tested at one time and was told it was fine.

This problem is driving me crazy.  Any and all input would be
appreciated.  Thanks again

Steve,

 

Here is some input.  At one point in the life of the Skymaster I flew, it had electrical system problems that had some of the characteristics you see.  Of course, the twin engined Skymaster had dual alternators and regulators where the regulators would trade control from one to another (flickering light problem) because they were designed to work in a resistance free environment.

 

Problems with the Master sw/relay:  Cheap Cessna switches would build up carbon on the contacts from arcing, thus introducing resistance in the Master relay holding circuit.  This resulted in weak holding power for the relay, thus its contacts could bounce in flight.  That can also build up resistance (carbon from arcing) on those contacts.  One noticeable result was poor starting because of greater voltage drop with even a small amount of resistance introduced into a high amperage circuit.

 

Problems with alternator:  The same type of cheapo switches were used for the "field" voltage and their introduction of unexpected resistance in that circuit caused regulator problems - of course, the other regulator would pick up the slack momentarily, then they would switch between the two.  Thus, the flickering light problem as they swapped which on was in charge (no pun intended).

 

Poor battery ground:  This creates all kinds of problems and exacerbates the ones mentioned previously.  Here, the aluminum airframe was the "ground" but if the path to the engine wasn't good because of the connection to the airframe, well........

 

When the aircraft was 20 years old with about 3000 hrs, I replaced the master switch, the alternator switches and the master relay.  What a difference as long as I kept the battery ground connection in good shape.

 

So what?  How does this story help you?  It is to point out that your problems may be the result of bad ground connections, bad switches, bad relays and poor connections with respect to the alternator, voltage regulator and bus - not to mention bad components.  For example, I placed my very good B&C voltage regulator on the forward face of the firewall.  Eventually, I cooked it because the temperature in the regulator area could easily exceed 70C, the operating limit for the regulator. The replacement has a blast tube pointed at it that keeps the operating temperature below 50-55C.

 

Good luck.