Rich Posted December 21, 2015 Report Share Posted December 21, 2015 Good evening, Just took my plane up after 6 weeks of inactivity. Remember on a previous thread, problems with the APIII, MP and RPM issues with my Tru Trak unit. They fixed the manifold pressure issue and the plane seems to fly level with the AP turned on. So bumpy it was hard to nail it down. The RPM readout still reads 700 RPM at 75% power. If it's not the TT unit, can it be the pickup in the engine? Something else? It reads correctly at idle but when the throttle is advanced it goes low again. Really frustrated at this point. Any help would be appreciated as always------Rich Link to comment Share on other sites More sharing options...
Anticept Posted December 21, 2015 Report Share Posted December 21, 2015 What have they done to address this issue so far? Do these steps in order, fixing as issues are found: Is there a trutrak setting that might affect this? Ask TruTrak support for any quick tips. Do you have another tach to plug into the tach cable from the engine as a quick and dirty test? If you don't have one, or the test tach works normally, read on. Make sure connectors are clean and snug (pins should not look deformed, and should have clean and firm engagement). This includes the tach cable from the engine, and the pins to the back of the trutrak unit. If this doesn't solve it, read on. Do a continuity check of the wires and pins. They should read near 0 ohms. Is the back of the engine easily accessed (in other words, is this a CT or is it something a lot easier?)? If so, have the pickup checked. If it's difficult to access, try step 4 first, it might save time. If the problem isn't yet solved, read on. Do you have access to an oscilloscope and know how to use it? The Rotax heavy maintenance manual describes what the tach signal will look like on a scope. Hook into the pins at the back of the trutrak unit. Tell us conclusions from it. If this is the last step for you, you really, really need to check it with a scope, because the last step could be expensive. If the scope is good, read on. RMA the trutrak unit. Link to comment Share on other sites More sharing options...
Rich Posted December 22, 2015 Author Report Share Posted December 22, 2015 Corey, The unit was sent back to Tru Trak for the above posted issues. They repaired both the EDM and APIII which leads me to believe it's some other issue. Will a regular tach be good enough to sense the Rotax pulses or is a special tach needed due to the two firings per cycle? Link to comment Share on other sites More sharing options...
Anticept Posted December 22, 2015 Report Share Posted December 22, 2015 You just need a tach that can sense 6k RPM. There's a small metal tab on the flywheel that the tach pickup senses. When you sent it back, did you tell them about the RPM issue? Link to comment Share on other sites More sharing options...
Rich Posted December 22, 2015 Author Report Share Posted December 22, 2015 Absolutely! That was an important item on the list. Link to comment Share on other sites More sharing options...
Anticept Posted December 22, 2015 Report Share Posted December 22, 2015 Throw an electronic tach on then and see what happens. Link to comment Share on other sites More sharing options...
Rich Posted December 22, 2015 Author Report Share Posted December 22, 2015 Corey, I called TT today and was told the tach system on the unit was checked and working properly. This leaves the pick-up or the connection points. I'm leaning towards the pick up unit. If that's the case, how much do you figure to get it fixed? Link to comment Share on other sites More sharing options...
Anticept Posted December 22, 2015 Report Share Posted December 22, 2015 Call me on my cell Link to comment Share on other sites More sharing options...
Rich Posted January 10, 2016 Author Report Share Posted January 10, 2016 Okay, The problem with the low voltage in the unit was solved and the bench check of the RPM's was done. So why the erroneous readout? When they bench tested the unit, the RPM setting was set to "4" instead of the number "1". I found the problem while waiting on a friend for lunch. Figured I'd take a look in the set-up menu. There are four settings in the TruTrak APIII for the correct tack readout. 1, 1.5, 2 and 4 All is well Finally! Link to comment Share on other sites More sharing options...
Anticept Posted January 11, 2016 Report Share Posted January 11, 2016 So I was spot on with my very first question? Having done IT, settings were the #1 reason things don't work as expected! Link to comment Share on other sites More sharing options...
Rich Posted January 11, 2016 Author Report Share Posted January 11, 2016 Corey, Thanks for your input. I had mentioned to them that it was reading a Rotax 912. If they sent it back with the correct setting it would have saved us some time. After calling them and verifying a good bench test, they said it had to be something not related to the unit itself. I had quite the smile when I put the setting on #1 and the tach responded as it should. Thanks again for you input and time. Very much appreciated Rich Link to comment Share on other sites More sharing options...
Anticept Posted January 11, 2016 Report Share Posted January 11, 2016 Make sure you notify them. It's quite an oversight and I'm sure they would want to know. Link to comment Share on other sites More sharing options...
Rich Posted January 11, 2016 Author Report Share Posted January 11, 2016 I had contacted them as soon as the problem was resolved. Link to comment Share on other sites More sharing options...
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