Alternator not putting out, or no Juice to the battery

[Pritch]

Charging system quit working last week so off to the Maintenance Hangar to check it out.  With the initial testing it showed that the voltage regulator was not functioning properly.  Ordered new reg. and installed, test flight, a little better but still not right, the only time I got 14 volts was on short final with next to no rpm's.  I/A said to pull the alternator, now this is a TSIO360 Continental so the Alt is mounted on the back of the case between the Mags.  2.5 hours later I have the Alt. off and back to the I/A to have him look at it.  One quick spin of the gear and he confirms that it is the coupler that has gone bad.  Two days and .9AMU's later I am reinstalling the Alt., another 2.5 hours of close quarters work.  Quick engine run up and everything is POSITIVE for charging.  Worse part is I had just put a new Alt. on two years ago, but used the old couple as it is more expensive than the Alt.  Good thing I am retired and have the time to tinker on the Mistress.

Pritch

[Mcstealth]

8 hours ago, Pritch said:

Charging system quit working last week so off to the Maintenance Hangar to check it out.  With the initial testing it showed that the voltage regulator was not functioning properly.  Ordered new reg. and installed, test flight, a little better but still not right, the only time I got 14 volts was on short final with next to no rpm's.  I/A said to pull the alternator, now this is a TSIO360 Continental so the Alt is mounted on the back of the case between the Mags.  2.5 hours later I have the Alt. off and back to the I/A to have him look at it.  One quick spin of the gear and he confirms that it is the coupler that has gone bad.  Two days and .9AMU's later I am reinstalling the Alt., another 2.5 hours of close quarters work.  Quick engine run up and everything is POSITIVE for charging.  Worse part is I had just put a new Alt. on two years ago, but used the old couple as it is more expensive than the Alt.  Good thing I am retired and have the time to tinker on the Mistress.

Pritch

Please take no offense to this question. 

With the regulator being down stream of the alternator,  why did the investigation stop there? Is the alternator and coupler hard to test on the plane? Do they need to be on the bench to test?

[Pritch]

5 hours ago, Mcstealth said:

.Please take no offense to this question. 

With the regulator being down stream of the alternator,  why did the investigation stop there? Is the alternator and coupler hard to test on the plane? Do they need to be on the bench to test?

The test show that the Alt was good, so next easiest to do is replace the reg. (lot easier that pulling the Alt. which is buried on the back of the case).  Next you have to pull the Alt off to check the coupler. So if you are paying an I/A to pull it a $110 an hour and at least 4 hours to R&R, one starts the easy way.  Fortunately the I/A know my capabilities and allows me to do most of the work under his watchful eye.

Pritch

[carusoam]

Somebody had a similar experience recently...

new alt and VR, to cure a slowly drifting voltage that creeped lower over years....

the wire that controls the voltage was slowly increasing in resistance.

Since wires don’t typically increase in resistance... the connection between the wire ends needed cleaning...

Fuzzy memory... of a PP, not a mechanic...

Best regards,

-a-