Flashing alternator lights
 

Hi All:

I have a T337D and both alt lights pulse, one then the other, then the other, etc. My digital voltage gauge shows the volts fluctuating between 26-28. It naturally pulses faster as RPM is increased. I thought it may be a bad regulator but it does it on either regulator. Anybody else ever have this occur? The only place I know where the two systems tie togther is thru the over voltage relay. Thanks, Jim

My first thought is how old is the battery?

Battery is fairly new and doesn't have any problem starting the engines.

I have a T337G and have been having intermittent problems and the only thing I have not looked at that I know of is the over-voltage relay....mine has never pulsed like yours....Hopefully a long term owner will know?

blinking lite
 

Flashing Alt Light My light never flashed and I didn't think I ever had a problem. Ate up a battery and had problem with the rear Alternate. When I installed a Aspen 1000 when my Hsi went tits up and I had some major work on the airplane. Gordon at AirTronics found I had some problems with the regulators not talking to each other and I had to replace something and now from time to time the alt lite will flicker from the the front to rear and Gordon says that is what it suppose to do. Give Gordon a call and drop my name and see what he tells you Gordon (406)-259-5006 Gordon is sarcastic so hang on he is a really smart lad and knows his stuff .
Good luck dave Jarrett

Flashing alternator lights is not an uncommon trait in Skymasters. It is usually caused by a high resistance point in your field wiring. The regulator senses field voltage to change alternator output. A high resistance point (and it might be just an ohm or two) causes "hunting" whereby system voltage is reduced a little bit by the resistance in the field circuit, causing the regulator to boost the output of the alternator, which overshoots. this also shows up as flickering instrument lights at night.

If a volt meter shows that your voltage is changing between between 26 and 28 volts, I would first inspect every connection in the field circuit, and then the bus circuit. Don't forget to measure across your field alternator switches and circuit breakers. They are often the source of the high resistance.

Once your have the path of least resistance verified in the field circuits, adjust each VR independantly to 28.5 volts, then see if the lights stay out. If not, then look at possibly defective VR,s or a problem with one of both alternators.

As far as I know (and I'm not an expert) the OV relay will only trip on over voltage, and then it will have to be reset. It should not cause a voltage fluctuation

That's some great info....Thanks!

blinking alt lights
 

Guys thanks for the replies. Mark your explanation sounds very plausable and a good place to start! And Dave I'll give Gordon a call as well. When we get this figured out I'll post the results. Jim

After reading the service manual I've decided to replace the alternator field fuses as they could be the culprit. Center of the forward firewall #214 fuses. They look good but I've seen that before and still bad...old and could be the cause,,,I'll let you know if that fixes it.

Brent

Had simular problem
 

In our case it was a very small short to ground in the balancing wire that runs between the alternators. Small problem that cost lots to trouble shoot due to its intermittence.
Sandy Loutitt
N81C

I don't know if the alternator field fuses were the culprit or the 6 year old alternator restart batteries, but the problem is now fixed with 10 hours and not a flash.:)

Problem solved
 

Well, I'm happy to report the installation of two Zeftronics regulators solved my flashing alternator lights problem. I still have a 1+- variation (less than the previous 3 volts or more) in voltage as the alternators cycle but that's probably due to some resistance in the alternator switches or circuit breakers.