What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Alternator Fail Light

iamtheari

Well Known Member
I have the IO-390 recommended for the RV-14, circa 2018. Not the fancy new one. And I have the RV-14 kit alternator. I wired the alternator failure wire from the alternator to my Garmin GEA 24 discrete input. Today, I took the maiden flight, and the alternator failure warning came on intermittently. The voltage and ammeter both looked healthy throughout the flight. Adding electrical load (pitot heat) did not clear the failure warning.

Has anyone had this happen to them? I fear a loose wire, but I want to rule out any other potential causes before I go digging in the panel again. I spent too long under that panel in 2020 and don't want to go back in just yet. :)

P.S. Build on! The end result is indescribably awesome.
 
I will have to think about the specific issue ( how the discrete is set, value the good/bad voltage of the alternator provides etc:how it works), but . . . voltage is the parameter that can determine if the alternator is working, even turned off. The G3X has a voltage alert/alarm setting and should be set to identify an alternator issue. Then you can use that discrete for something else.
 
Last edited:
Alternator fail light circuits are designed for a low impedance load such as an incandescent light bulb. You will likely have to add a resistor to ground to get the indication to work properly.
 
What mine does.

On my -4, I have a basic Denso alternator i bought through VANs. The "fail light" is a simple red LED I bought from Radio Shack. When engine is off and master is on the light is bright red, when running and operating normally, it is a dim glow. I have had the indicator light lead wire spade fitting break and the light goes out completely. I also had the field wire spade break and the light becomes very bright warning me as designed. I have replaced all the cheapo spade terminals with good ones. I have heard others that have the same dim light or flickering at low RPM.
 
Congratulations on your 1st flight! :D

I have a low-voltage alarm on the G3x to alert for alternator failure. Works well.
 
Alternator fail light circuits are designed for a low impedance load such as an incandescent light bulb. You will likely have to add a resistor to ground to get the indication to work properly.

Thanks. I’ll look at the alternator manual a bit closer. And as others have pointed out, the voltage reading is probably a better source for an alternator failure warning, so I may just abandon that wire and configure the G3X to light up my yellow annunciator when the voltage is below 14V.
 
Back
Top