Installing a Horizon P-1000 tachometer
I just replaced my old mechanical tachometer with a shiny new [http:// www.horizoninstruments.com Horizon P-1000 digital tach].
Certification
The P-1000 is STC'd as a replacement for our mechanical tachs, so the paperwork is minimal: log book entry and 337 approved by an IA.
Ordering
I ordered mine directly from Horizon Instruments and, with 2-day shipping, received it in a couple of days. When ordering be prepared to provide all the specifics of the aircraft: make, model, serial number, N-number, owner, and engine model number. Horizon can set the hour meter on the new tach to match your old one if desired, so have that number handy as well. I had my airplane down for annual at the time, so it made sense to match the meter readings and avoid more math going forward.
In the box
The package came with almost everything needed, including a circuit breaker, wiring harness, and paperwork.
Installation
The installation was straightforward, and followed the supplied installation instructions. The only thing I had to work at was getting the circuit breaker installed, since the supplied breaker is a different size and configuration than the original breakers. I have room where the original factory breakers were installed on my 1979 Tiger, but I could not obtain a 1-amp breaker in that form factor. I ended up mounting the Horizon-supplied breaker there, and used a short bit of wire to connect it to the bus.
The instructions say to not cut the mag wires. I was concerned that the extra wire under there might cause some interference in the audio system, but none was observed when the system was tested.
I thought about removing the old tach cable housing intact, but after noticing all the other wires and cables going through that hole, I decided to just cut it and remove the pieces.
Operation
On run-up the tach performed as advertised, although the 1-RPM resolution seems to make it a bit jumpy. I think we were seeing RPM changes just from the wind that wouldn't be noticed on a mechanical tach. I'll report more after we get a chance to fly it.
