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Electronic Tachs


There was a thread on this a while back, but didn't find it. I have a Horizon electronic tach in an airplane with an O-360, which recently started flashing a red light at me intermittently. A study of the POH for the tach didnt' reveal what this signal meant.

In conjunction with this, started getting weak starts, as in just barely catching, and running grudgingly.

Talked to the mechanics about the issue, and couldn't come up with answers. Mag checks were normal.

Took the mags apart, and the left one was total junk inside, as in pieces of metal rattling around inside. It was still firing, but the mechanics said they don't understand how.

That was the mag the electronic tach was flashing a red light on. So, maybe the tach is better than I thought.

And I liked it anyway. For what it's worth,


Dang, I knew there was something going on that light was telling me.

Might explain why one mag was trash and the other was like new.

Or not.

We missed you the other night, but we talked about you a lot. Whoooeee!

Having never used an electronic tach.... does installing one of these allow you to do away with the mechanical unit?

Same question goes for the digital temp and pressure gages. Is it the right thing to do?? Worth the money?

The tach I'm using is the Horizon digital tach, and it is approved as primary, and is stc'd for various aircraft. There are also a couple other tachs that are approved as primary.

Before buying any of these things, make sure that a) they are approved for primary information. If not, you have to leave the stock gauges in place also, which makes no sense.

And, b) make sure that they are either stc'd for your airplane, or that your mechanic can install them as a direct replacement, under his or her authorization as a minor alteration.

I have the Horizon tach on a O-320, PA-18. It, gets rid of the tach cable and gives some additonal diagonstics. Just installed the BC oil filter adapter and was glad the tach cable wasn't there to deal with. Had enough issues with the big blue capacitor and voltage regulator. Anyway, the diagnostics make the mag check a little different. When you switch mags the digital presentation from the tach kinda processes, with a lag, then displays the RPM for the mag selected. Its something you get used to.

I also have the Electronics Internatinal tach on another airplane and it is great. The EI tach does not have the diagnostics so is very simple read would probably lean towards EI if I was doing it again.

On my Digital Horizon Tach when you the mag check it shows the amount of mag drop. ie: -78 or what ever the drop is on that mag very nice indeed. It is a great tach.
I just installed an EI digital tach. I like it a lot.