Intermittent High Voltage

I had my first flight of my plane today. The only issue I had was an intermittent high voltage warning 15.0 volts. Amps were always in the green at +2-3 amps. I landing the plane and checked the grounding between the voltage regulator and the battery. It was OK, but I went ahead and removed the VR and made sure the ground to the airframe was good. I also added a ground strap from the VR to the engine. Second flight, same thing, intermittent High Voltage. Could I have a bad battery?? Help

One time I had intermittent high voltage but my amps were also oscillating. It turned out to be a loose connection where the fat wire tied into the buss bar.

Danny King said:

My orginal Voltage Regular was a low cost solid state unit purchased from Van. On a very cold day it locked up sending full voltage to the alternator field, triggering a high voltage spike like you experienced. That fried power amplifier in my RC Allen electric DG which cost $400 dollars to repair.

Realizing that I was very lucky to only fry one item, I learned my lesson and ordered the B&C LR3C-14 Alternator Controller/Regulator, 14v for $288 dollars. That unit is liner not an on/off switching type, and will not allow over voltage spikes. I was trying to save money by using the cheap VR but the RC Allen repair was much more expensive than the B&C regulator.

I doubt that your battery is the problem!

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This is in the RV-12 forum, so B&C regulator wouldn't be an option.

No, the problem is NOT a bad battery. The problem is either a bad connection in the regulator terminal "C" circuit or a bad regulator. Remove the electrical connector from the regulator. Connect an automotive taillight bulb to the female "C" faston and to the regulator case and turn on the master switch. The bulb should light up. Measure the voltage across the light bulb using the regulator case as the reference point. The voltage should be pretty close to the same as the battery voltage. If not, measure voltage at various places to find out where the voltage is being dropped. The taillight bulb puts a load on the circuit to make a bad connection show up better.

Joe,

When you die we will have to preserve your brain for this forum!

Rich

Joe,
so, if there is a break in connectivity, the voltage will read high? I was getting 15.0- 15.8 volts. (Intermittently) I would logically think if there was a break in connectivity my voltage would go to zero.

Jim

jsenft said:

Joe,
so, if there is a break in connectivity, the voltage will read high? I was getting 15.0- 15.8 volts. (Intermittently) I would logically think if there was a break in connectivity my voltage would go to zero.

Jim

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Think of that wire as a voltage sense/detection line.
If it sees the voltage on the wire go below a specific value (buss voltage low because of a low battery, excess load, or both) the charging system attempts to compensate by raising the voltage.
So, if the wire has a poor connection somewhere (causing a voltage drop) or intermittently disconnects entirely, the regulator sees a reduced voltage and attempts to compensate by raising it. If it is getting false information, it can raise the voltage higher than the normal value.

so, if there is a break in connectivity, the voltage will read high?

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No, aircraft system voltage will drop to battery voltage.

I would logically think if there was a break in connectivity my voltage would go to zero.

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No, regulator output will go to zero, but aircraft system voltage will be at battery voltage.
According to what Bob Nuckolls posted message 6, if the voltage on regulator terminal "C" goes to zero, then the regulator will shut off. Terminal "C" is both an on-off control and voltage sense. If the regulator shuts off, the electrical system voltage will be equal to battery voltage.
Like Scott said, a poor connection will cause the voltage to go high. A poor connection means there is unwanted resistance in the circuit, but not an open circuit.
Have you done the test that I suggested in post 5 above?
Here is another idea: SV-EMS-220/221 pin 2 is an unused voltmeter input. Connect a wire from pin 2 to regulator terminal "C' and go flying. If the aircraft system voltage goes high, then land and download the SkyView data log and analyze the voltage on pin 2 to see if it varied. If the voltage on regulator terminal "C" is always equal to aircraft system voltage, then the regulator is at fault if the voltage goes high.

Joe & Scott,
You nailed! It was a loose ?C? connector. This tab on the spade connector was not engaged in the housing. Pulled it out, bent the tab, Bingo Fixed. Thanks
Jim