[Sixes350]

Good guess Atari. Has a Rhino alarm fitted. Siren box is switched off but everything else works. Am thinking about getting a new one put in as that will enable me to sort and clean up some of the wiring.

[rick1970]

Interesting....

Anyone like to hazard a guess if this would also work to correct a tacho signal? The tacho is currently run by a 'W' terminal (phase) on the alternator, and due to changing pulleys and alternators, now reads somewhat higher than the engine is actually doing. This is on a Range Rover.

[Sixes350]

Depends on the signal input voltage and if it is linear

[rick1970]

from my understanding, the w terminal is just linked to one of the phase's of the alternator....

[Sixes350]

You will have to find out the signal voltage and if it is a linear signal. Or check if there is a tap off the ECU for a tacho

[rick1970]

not sure what you mean by linear signal. The ECU picks up its engine rpm signal via the coil as a normal tacho would. The ECU is basically a Lucas made copy of the old Bosch L-Jetronic (flapper AFM) system. The setup with the tacho running of the alternator is factory Rover, just the alternator drive ratio has been changed.

Or maybe just machine up a new alternator pulley of the appropriate size would just be an easier way around it.....

[Sixes350]

The Jaycar kit won't work off variable voltage signal (curve). It has to be linear (straigt) similar to a fuel gauge sender if you know what I mean

[rick1970]

ah yeah.....ok. Ta

[fordem]

Sixes350 wrote:

The Jaycar kit won't work off variable voltage signal (curve). It has to be linear (straigt) similar to a fuel gauge sender if you know what I mean

Maybe I'm missing something - as far as I know the jaycar kit is digital and counts pulses - it won't work off a variable voltage either linear or curved - I see no reason why it can't work off of an alternator output provided the signal is suitable conditioned - the output of a single phase from an alternator is going to be a sine wave with the frequency varying with rpm, you'll need to use some sort of a comparator to change that to a rectangular pulse - theoretically not very difficult.

There's also a possibility that you could "out run" the Jaycar kit since the alternator output is going to be running significantly faster than the speedo drive it's designed to work with.

[rick1970]

fordem wrote:

Sixes350 wrote:

The Jaycar kit won't work off variable voltage signal (curve). It has to be linear (straigt) similar to a fuel gauge sender if you know what I mean

Maybe I'm missing something - as far as I know the jaycar kit is digital and counts pulses - it won't work off a variable voltage either linear or curved - I see no reason why it can't work off of an alternator output provided the signal is suitable conditioned - the output of a single phase from an alternator is going to be a sine wave with the frequency varying with rpm, you'll need to use some sort of a comparator to change that to a rectangular pulse - theoretically not very difficult.

There's also a possibility that you could "out run" the Jaycar kit since the alternator output is going to be running significantly faster than the speedo drive it's designed to work with.

Cheers.
a correctly sized alternator pulley sounds like it may be the better approach...