Nippon Denso tests good, panel indicates overvoltage

cojaken · #1 03-17-2019, 01:15 PM

The title pretty much say it all. The panel indicates the voltage is varying from about 14.5 to 16,5. I decided to take the alternator, which is a Nippon Denso part # 14684 out and have it tested.

O'Reilly and Advance Auto both said it was good including the voltage regulation.

I would appreciate suggestions for next steps please?

rv7charlie · #2 03-17-2019, 03:14 PM

1st thought is to verify instrumentation (no mention of what 'panel' is) by hooking up a known-good volt meter you can monitor in flight.

2nd thought is to check on your hookups to the alternator. 1st link to a wiring diagram I could find:
https://www.goldwingfacts.com/forums...-alt-pix-2.png
The IG terminal must go high to turn it on. The S terminal may or may not be required for stable operation, depending on the specific regulator in your alternator. If needed, it can be jumped directly to the B terminal, or it can be run to the battery + terminal, or to the bus. It's intended to tell the regulator what the voltage is *at the load*, which allows the alternator to deliver setpoint voltage at the load, compensating for voltage drop in the path to the load.

3rd thought (a bit of a stretch, in this case) is poor connections (particularly ground paths) causing false readings in the 'panel'.

Charlie

cojaken · #3 03-17-2019, 04:28 PM

The ?panel? is an Advanced Flight Systems AF3500EM

rv7charlie · #4 03-17-2019, 05:13 PM

Then if everything else is 'nominal', you can probably assume that the engine monitor wiring isn't the problem, though the volt meter function *might* have an issue. Clip an standalone digital meter to the bus, and go fly, to compare the AFS voltage reading to a digital meter's reading.

Or try the 2nd thought, if you don't have a volt meter handy at the moment. No meter needed to check the connections on the back of the alt.

snopercod · #5 03-17-2019, 05:15 PM

That looks like the kind of alternator I have. My external voltage regulator is a B&C LR3C-14 linear voltage regulator. Yours? I'm guessing your problem is either with your voltage regulator or the interconnecting wiring. I agree with Charlie that you should hook up a good voltmeter to eliminate instrumentation error.

rv7charlie · #6 03-17-2019, 05:44 PM

That particular model has an internal regulator, if it hasn't been modified.

cojaken · #7 03-17-2019, 07:13 PM

It has the internal regulator and has not been modified. I will check the continuity of all the connections and hook up an external voltmeter to cross check the AF3500EM as you sugggest. Thanks so much for the input.

vlittle · #8 03-17-2019, 08:54 PM

Quote:

Originally Posted by cojaken

It has the internal regulator and has not been modified. I will check the continuity of all the connections and hook up an external voltmeter to cross check the AF3500EM as you sugggest. Thanks so much for the input.

99.9% certain you have a bad connection, bad breaker or a bad switch on the ALT Field circuit.

Mich48041 · #9 03-17-2019, 08:57 PM

With the engine not running and the master switch turned on and alternator field switch turned on, measure the voltage drop between the main power bus and the alternator field terminal (if there is one). There should be very little voltage drop.

cojaken · #10 03-18-2019, 05:54 PM

I have done some more information gathering, but not completed the process yet.

The only terminals connected on the alternator are the B (output) terminal and the IG (ignition switch) terminal. Terminal L (warning lamp) and S (battery voltage sensing) are not connected to anything.

I downloaded the data from the AF3500EM and note that up until 111 tach hours the voltage was usually less than 14.5v. After 111 hours very brief periods of instability up to 15.5v began to appear. However during the last hour from 118 to 119 (current), 16v, 17v and even momentarily 18 volts were recorded.

Even in the last hour, the voltage stayed below 14.5 for periods, so it does seem like an intermittent fault. I wonder if this suggests an intermittent regulator problem?

I am not questioning the wiring design as everything worked great for 110 hours, so I will be checking for a bad connection, breaker or switch, or voltage drop as suggested. Next time I will be flying with a digital voltmeter to cross check the AF3500 values.