Philip Welsch Posted October 11, 2015 Report Share Posted October 11, 2015 What voltages are you guys with EMS 120s seeing: prior to start, at or above 5000rpm, with and without autopilot engaged. My Dynon indicated voltage has degraded from 13.5/.6 at 5000rpm (ap off) in 2008 (730 hours ago) to 13.1/.2 at present. I have replaced the voltage regulator and the battery without significant improvement. A temporarily installed voltmeter wired through a fuse directly to the battery indicates 13.55 - 13.77 volts at 5000 rpm while the Dynon (wired to the power buss) shows .4 to .5 less. When the autopilot (trutrac) is engaged both voltmeters indicate .2 - .3 volts less. Starting the engine is not a problem. Any thoughts? Philip Link to comment Share on other sites More sharing options...
Anticept Posted October 11, 2015 Report Share Posted October 11, 2015 Check voltage from pin 1 (master power) on the db 37 connector to pin 3. The voltage you read is what the EMS will see. Also, check pins 5, 16, 17, and 30 for the hell of it (these are also ground pins). I suggest that as there might be another lower resistance ground. I'm willing to bet that is where you will find a discrepancy. Also, your temporary voltmeter can also be off. Other than that, the obvious: the D120 voltmeter is not be reading correctly. Link to comment Share on other sites More sharing options...
Roger Lee Posted October 12, 2015 Report Share Posted October 12, 2015 Those are fairly normal Philp. Each person may be +/- a tad on individual planes. Link to comment Share on other sites More sharing options...
Anticept Posted October 12, 2015 Report Share Posted October 12, 2015 What is not normal is how his readings have gone down. Link to comment Share on other sites More sharing options...
Roger Lee Posted October 12, 2015 Report Share Posted October 12, 2015 "voltmeter wired through a fuse directly to the battery indicates 13.55 - 13.77 volts at 5000 rpm" "When the autopilot (trutrac) is engaged both voltmeters indicate .2 - .3 volts less." This is still very normal and may be just wear and tear from age, corrosion and parts aging. So long as he isn't having any issues you may be chasing a ghost. The Dynon tends to read .5 volt lower than the system's real voltage for most anyway. Link to comment Share on other sites More sharing options...
Anticept Posted October 12, 2015 Report Share Posted October 12, 2015 That's why I was suggesting checking the pins. It's a really easy test :-). It's not going to do much other than verify that system voltage is actually getting to the dynon, but it would eliminate a bunch of other possibilities. After that, it's up to Phil if he wants to take it any further (which would involve wiring a diagnostic harness in to check voltage while under load to test voltage drop). As you said, it's probably nothing to worry about, but it's always worth a quick simple check. Link to comment Share on other sites More sharing options...
Roger Lee Posted October 12, 2015 Report Share Posted October 12, 2015 I have talked with Philip. He's done a pretty good job of troubleshooting. Link to comment Share on other sites More sharing options...
Anticept Posted October 13, 2015 Report Share Posted October 13, 2015 Good looking out Link to comment Share on other sites More sharing options...
Roger Lee Posted October 13, 2015 Report Share Posted October 13, 2015 I'll see Philip Thursday so I'm sure we'll have some more discussion. Link to comment Share on other sites More sharing options...
Anticept Posted October 13, 2015 Report Share Posted October 13, 2015 Hey roger, if you haven't already, you should make up some diagnostic harnesses. Basically they would be short harness that you insert into the system between the avionics socket and factory harness, with a third socket pig-tailing off for diagnostic hookups. I'm going to be doing that soon, maybe I could make up a couple extra sets for you (I just need to know what socket specification you need). Will make it a lot easier to test the live system. Picture of one: http://img.curiousexpeditions.org/nimg/76/7a/931402d3dc254e0266ba3c13f933-600x600-0/auto_obd_diagnostic_harness_for_japanese_car.jpg Link to comment Share on other sites More sharing options...
Roger Lee Posted October 13, 2015 Report Share Posted October 13, 2015 Hi Corey, Just to do a quick check you just need to unplug the connector in the engine compartment over by our battery and plug a little cheap rpm test gauge in and run it and see if it does it then. If it does it is the trigger coil or air gap and if it is okay then it is the instrument. You could make a test gauge with a cheap tach and some wire. Link to comment Share on other sites More sharing options...
Anticept Posted October 13, 2015 Report Share Posted October 13, 2015 Hi Corey,Just to do a quick check you just need to unplug the connector in the engine compartment over by our battery and plug a little cheap rpm test gauge in and run it and see if it does it then. If it does it is the trigger coil or air gap and if it is okay then it is the instrument. You could make a test gauge with a cheap tach and some wire. Wrong thread ;-) Link to comment Share on other sites More sharing options...
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