I think I noticed one of the D581 type have weak spark
shortly before complete failure. I am still using three of the D581's
just to proove to myself that it was a heat problem that caused several
failures before I put a cooling plenum around them.
I have heard no reports of the D580 type failing
(even without a cooling plenum) but I still recommend an enclosure with a
supply of cool air to them. We are pushing them pretty hard in aircraft
use.
My coils are mounted on top of the
engine where the temps are typically about 140 -150F range, and have operated
there for about 60 hours. Early in the test program I did not have an aux fan
on the in-cowl rad, and I’m sure the temps after shutdown went higher. I
now leave the aux fan run for awhile after shutdown.
On testing them the other day using mode
8, all 6 still jump a spark 1 ¼”+. I was concerned earlier when I had
checked than while cranking with the starter, and it was hard to getting more
than 1/8” jump. Have no problems starting, but it seems the output is
quite sensitive to voltage; and may be among the first reasons for loss of
power following an alternator failure.
I guess I have D580’s, but I don’t
know what the difference is from a D581.
Al G