[Paul 5r4]

N729PG first flew a month ago. Have been working out the little bugs that come up during/after that first flight. One of mine was the dynon tach was erratic. First I had done the resistor value increase per the dynon manual. Got all the way up to almost 100k with no change. Then I put in the hall effect sensor like some of the others had done on here. That at first seemed to have fixed the problem. Then after a couple of flights, it was back however after a minute or two after takeoff it would be rock solid thru all rpm ranges. I had kinda resolved myself that I may just have to live with it. Then a few days ago, my egt reading on number 3 shot up to 2000 degrees! I knew this was an electrical problem as the engine sounded no different and was running fine. So one more time I took the cowling off and looked around. I had read about electrical interference from one wire to the other. I looked at the egt wire run and the hall effect sensor wire run and sure enough they were in close proximity... about half inch apart... for about 4 inches before each split off to go their own way. My son, (X F-18 electricians mate in the navy), had told me to try wrapping a little foil wrap around one of them to shield the wires from each other where they were in close proximity. I cut some strips of foil and wrapped the hall effect sensor wires just like I was wrapping them with black electrical tape then re zipped tied them in pretty much the same place they were in. WALA.... both the tach and egt issues are gone!!! I'll also bet that if I had tried this back in the beginning when I was still using just the dynon leads to each tach, it probably would have fixed the problem. Anyway.... hope this helps someone in the future. Keep pounding the rivets... it is worth it!

 

[vlittle]

My guess is that will not fix your problem. You seem to have a grounding problem.

Alternatively, your comm radio may be interfering when you transmit.

You may want to dig further.

 

[Paul 5r4]

Again.... really!

Looks like you're right Vern. After a flight or two of good readings, the tach and egt issue is back. Like you said, I'll be digging a little more.

 

[Pmerems]

High EGT solution

I believe you will find that one of the #3 EGT probe wires is not making a good connection. When this happens the reading goes to approximately 2000 degrees. I had this happen after about 20 hours into my phase 1 testing. The failure was a loose factory crimp on the probe wire. I replaced the Faston connector and made sure the crimp was good.

If you crimped your own connectors on the probe wires check them first. If you don't find any issues look to the back of the connector on the Dynon. You can investigate this on the ground with the Dynon turned on. Just don't short the wire to ground (if you find one loose).

I hope this helps.