High current alarm

Returning from Oshkosh yesterday, I received five intermittent high current alarms from my D-180. Switching to the electrical screen, the current value bounced around but generally stayed in the green. But it would occasionally spike to 18-23 amps then immediately drop back to normal. The last hour of the flight was uneventful. The voltage remained normal. I did switch off the auto pilot but that had no effect. I did not notice any odors. My first thoughts are a defective voltage control, then maybe a chaffed wire or loose connection. Any other suggestions will be welcome.
Frank

I am suspecting the voltage regulator, mine acted the same way at 250 hours and it was intermittent. The slsa 12's now have the regulator mounted in the cockpit above the passenger's knees. The 12 I am building now will have it mounted there also. I don't have any proof of this, but I think if you have any slack in the conduit that runs from the plenum horn to the voltage regulator (assuming you have the lighting kit), you could pull the conduit in the horn and turn it 90 degrees, secured by a tie wrap into the air stream coming through the scat tubing, thus forcing more air to the regulator. That regulator gets hot. The temp. strip on my previous 12 recorded 150 degrees before the little mod.

If the voltage remained normal, than the dynamo and regulator / rectifier are working fine. If the current spikes, I would suspect either a faulty ammeter (most likely) or an intermittent heavy load. My D-180 ammeter has never worked right. Others have said the same about their D-180 ammeter. I do not know if the problem is within the D-180 or with the shunt inside of the control board. As long as the voltage remains normal, I am not concerned about the ammeter fluctuations in my RV-12.
Joe Gores

shunt??

Timely post. Yesterday I flew my -8 and had the first ever current alarm from my D-180. I looked at the data and voltage remained very steady around 14 or so volts. The current however showed a spike up to about 40 amps, and one spike up around 74 amps.

As it is a 60 amp alternator I suspect faulty readings are the issue. Why?... dunno. The connections across the ammeter shunt are most likely the problem. A very small change in resistance across the shunt can result in huge "amp" swings.

Something to watch in the future.

Don

Mich48041 said:

If the voltage remained normal, than the dynamo and regulator / rectifier are working fine. If the current spikes, I would suspect either a faulty ammeter (most likely) or an intermittent heavy load. My D-180 ammeter has never worked right. Others have said the same about their D-180 ammeter. I do not know if the problem is within the D-180 or with the shunt inside of the control board. As long as the voltage remains normal, I am not concerned about the ammeter fluctuations in my RV-12.
Joe Gores

Click to expand...

I was hoping Joe would comment on this. In thinking back, my voltage was very inconsistent and I was getting alarms regarding it. I know quite a few have had problems with the regulator. Once again, I think Joe nailed it.

Just out of curiosity I wonder what the short circuit current is for the alternator. If the amp reading is higher then it would definitely be an indication problem.

Alternators are self current limiting. If the output is shorted the current would go up, but the voltage would drop. Since the voltage remained normal for Frank, then it is an indication problem (ammeter or shunt).
The way the shunt is wired in the RV-12 with the D-180 (I assume the Skyview is the same), the ammeter shows current into or out of the battery (and the 5 amp cigar outlet). It is very unlikely that the battery was charging at 23 amps. An overload or short circuit elsewhere in the electrical system would cause a voltage drop and a negative reading on the ammeter as the battery tried to help the alternator supply the load.
Joe Gores

I inspected the wiring this afternoon and found that the wire P156 going from the regulator to the starter solenoid had an abrasion or small notch cut into the insulation where it crosses the double bladed longitudinal stiffer on the firewall shelf. See photo. During previous inspections, there was always some clearance but perhaps under operation the wire might have vibrated vertically and contacted the stiffener. After rubber-tubing the wire, a test flight didn't reveal any problems but I will continue to watch for alarms. Thanks to all for your input, very helpful and useful. Frank

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