Jabiru/Dynon D-180 Tachometer

[N111YX]

Greetings all.

I am having the 1 amp fuse between the alternator and the Dynon tach connection blow repeatedly.

I did just install a new alternator stator but I cannot understand why that would cause the problem when all of the other electrical indications are normal. With a new fuse, the tach reading will fluctuate for about 10 seconds at or just above idle then drop to zero when the fuse blows.

Help me understand please...per my drawings, the fuse and wire to the Dynon tach input is tapped from one of the two alternator wires directly and is apparently not influenced by the regulator despite the same wire going to the regulator. So, how was it that the alternator output which is obviously greater than one amp, not blowing this fuse all of the time (disregarding my problem now) with this setup for 10 years without problems? It has occurred to me that the wires from the alternator may be specific but I am under the impression that it makes no difference with regards to where they go ie., swappable. I'm curious about this tach pickup arrangement and fully admit that electrical stuff is not my specialty.

I have a message sent to Dynon Tech but have not heard back in 24 hours and it seems that they are working from home and perhaps backlogged.

Thanks,

[Panther16]

Normally only 1 alternator lead will work for a tach pickup. Try the other lead first. I have the same eng D180 combination. I use both tach inputs to the D180. One uses the left mag and the other input uses one alt lead. I also switch the alternator on and off with 2 relays, one for each lead. I also had to change the alternator stator with no problem. My alternator pick up is fused and the mag pick up is not.
Keith Rhode
Sonex s/n 1009

[N111YX]

I'll swap the leads and hope it's a simple fix.

Thanks,

Kip

Normally only 1 alternator lead will work for a tach pickup. Try the other lead first. I have the same eng D180 combination. I use both tach inputs to the D180. One uses the left mag and the other input uses one alt lead. I also switch the alternator on and off with 2 relays, one for each lead. I also had to change the alternator stator with no problem. My alternator pick up is fused and the mag pick up is not.
Keith Rhode
Sonex s/n 1009

[sonex1374]

Kip,

If swapping the tach to the other alternator pigtail wire doesn't help, you might consider placing a resistor inline with the fuse. The resistor will reduce the amount of current that can pass thru the fuse and may drop it back down to a manageable level. I use a 10k ohm resistor in my Skyview tach pickup, and it helps smooth out the tach signal as well (without it the tach was a bit unstable and slow to respond to rapid power changes). Even a small resistor (like 100 ohm) should make a big effect on the current that passes thru that fuse, so if the 10k ohm for some reason doesn't allow a reliable tach signal you can reduce the resistor value until you find the sweet spot that does work.

You can splice/solder a resistor into the tach wire directly, or you can crimp the resistor to a male and female fast-on tab (making a short jumper wire with connectors on each end), then insert it at the existing alternator connector.

Jeff

[N111YX]

That's great advice, Jeff.

Thank you!

Kip

Kip,

If swapping the tach to the other alternator pigtail wire doesn't help, you might consider placing a resistor inline with the fuse. The resistor will reduce the amount of current that can pass thru the fuse and may drop it back down to a manageable level. I use a 10k ohm resistor in my Skyview tach pickup, and it helps smooth out the tach signal as well (without it the tach was a bit unstable and slow to respond to rapid power changes). Even a small resistor (like 100 ohm) should make a big effect on the current that passes thru that fuse, so if the 10k ohm for some reason doesn't allow a reliable tach signal you can reduce the resistor value until you find the sweet spot that does work.

You can splice/solder a resistor into the tach wire directly, or you can crimp the resistor to a male and female fast-on tab (making a short jumper wire with connectors on each end), then insert it at the existing alternator connector.

Jeff

[N111YX]

Follow up...

I took both of Jeff's bits of advice. I sought a $0.03 resistor from Amazon (since there are no more Radio Shacks) and I ended up with about 630 of them in a bulk $8.99 package.

However, I swapped the alternator wires first and I have run five hours without the fuse blowing. So, I am left wondering why the wire swap fixed the issue because they are not labeled in any way so it seems they are "equal and indifferent" with regards to installation. No resistor required as of now.

At this point I don't really care about wasted resistor money because everything is running fine and I hope it continues all the way to the 1000 hour mark. Only 140 more hours to go.