ArtVandelay Posted October 18, 2014 Report Posted October 18, 2014 My low voltage light comes on, flashing or more like flickering, when it's flashing my voltage is a solid 13.4v and ammeter is on the + side. Makes me think it's a indicator problem, the maintenance manual shows a circuit, my questions are: Is my diagnosis correct? Where is this circuitry? Do you really have to replace individual electronic components or is it a black box? TIA Quote
Marauder Posted October 18, 2014 Report Posted October 18, 2014 My low voltage light comes on, flashing or more like flickering, when it's flashing my voltage is a solid 13.4v and ammeter is on the + side. Makes me think it's a indicator problem, the maintenance manual shows a circuit, my questions are: Is my diagnosis correct? Where is this circuitry? Do you really have to replace individual electronic components or is it a black box? TIA Which year Mooney? I think there is a difference between years and models. Quote
ArtVandelay Posted October 18, 2014 Author Report Posted October 18, 2014 Which year Mooney? I think there is a difference between years and models. 78 J Quote
Marauder Posted October 18, 2014 Report Posted October 18, 2014 78 J My F will shows the light when the voltage gets down into the low 12 range. 13.4 is higher than it should be. Does it go out when you add power? Quote
ArtVandelay Posted October 18, 2014 Author Report Posted October 18, 2014 My F will shows the light when the voltage gets down into the low 12 range. 13.4 is higher than it should be. Does it go out when you add power? Nope, it's random, usually takes about 45 mins, then it starts flickering, then it stop, then it flashes, then it flickers, then it goes out, etc etc This is at cruise power, the 13.4 tells me the alternator is working, I pull the alt field, the voltage drops as expected, pushing the CB back in returns voltage to 13.4 and low voltage light continues its erratic behavior. Quote
Marauder Posted October 18, 2014 Report Posted October 18, 2014 This is bringing back memories. I dealt with this way back in the 90s. There is a diode somewhere in the circuit that failed in my case. My annunicator is watered down version of your annunicator. Take a look at the wiring schematic for a diode inline before one of the Molex connectors. Quote
Bob - S50 Posted October 19, 2014 Report Posted October 19, 2014 We've had similar problems with our '78 J. In our maintenance manual on page 12-98 it addresses adjusting the settings. While we didn't bother, it can be adjusted. The light still occasionally comes on. When it does, I just confirm that the JPI voltage still indicates something around 13.5 or so and press on. The manual says...  6. Hi/Low Voltage Waring Circuit - Annunciator Panel. Remove annunciator top cover. Connect a voltmeter to the aircraft bus. Start engine and run at idle. Add load to bus until "Low Volt" light starts to flash. Adjust RPM to obtain bus voltage of 12.5 volts (24-0001 thru 24-2999); 26.5 volts (24-3000 thru 24-TBA). Adjust trim pot located at center, rear of circuit board until flashing light just comes on.  Note: It may be necessary to adjust trim pot to turn out lights at 12.5 volts (24-0001 thru 24-2999); 26.5 volts (24-3000 thru 24-TBA) first. Increase RPM until light goes out and note voltage. Decrease RPM until light flashes on and note voltage. Light should come on at a voltage between 12.4 and 12.6 volts (24-0001 thru 24-2999); 26.4 and 26.6 volts (24-3000 thru 24-TBA).  Good luck,  Bob Quote
Piloto Posted October 19, 2014 Report Posted October 19, 2014 Most likely you have dirty contacts. Remove the back connector and spray contact cleaner on the pins.  José Quote
ArtVandelay Posted October 19, 2014 Author Report Posted October 19, 2014 Re: Jose, Bob, the problem is it's not recreatable on the ground, only occurs after flying for a while, like 45 mins, I'm probably going to have to wait until it fails all the time, I'm guessing when the electronics heat up a little it goes into failure mode. Quote
mike_elliott Posted October 21, 2014 Report Posted October 21, 2014 Clean the master switch terminals. Sounds silly, but try it, you might be surprised. Quote
mbmaksymdc10 Posted October 29, 2014 Report Posted October 29, 2014 My low voltage light comes on, flashing or more like flickering, when it's flashing my voltage is a solid 13.4v and ammeter is on the + side. Makes me think it's a indicator problem, the maintenance manual shows a circuit, my questions are: Is my diagnosis correct? Where is this circuitry? Do you really have to replace individual electronic components or is it a black box? TIA Quote
mbmaksymdc10 Posted October 29, 2014 Report Posted October 29, 2014 Go under the glare sheld and adjust the pod its in the mooney maintenance manual Quote
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