Tachos Not Working. Help

[deisel]

I Just Brought 2 New Tachos For My Perkins Diesel Engines, But Cant Get Them To Work. + & Neg Connected, & The Wire
To The W Terminal On The Alternator, Nothing! There Are 2
Connectors On The Tachos Which Go To Sensors On More Modern And Or Petrol Engines Which Are Not Supposed To
Be Used When Using The "W" Terminal, Any One Got Any Ideas?

 

[alan006]

If they are the same type as I have just fitted, you need to set the ratio by moving a little screw on the back. The ones I fitted had a choice of about 5 ratios, it was a suck it and see type job.

 

[deisel]

Yep Tried This But Still Got Nothing!

 

[Anthony]

Did you have any tachos before, were they working, if so do they still work if you hook them back up? Are you def getting a voltage on the laternator signal lines?

Ants

 

[steve28]

measure the voltage on the w terminal, its ac, see if you have output. i dont think you have

 

[alan006]

Sorry if this seems too obvious, but there are two positives on the back of the rev counter. One provides power to illuminate the meter the other powers the meter. If you have only connected one positive that might be your problem.

 

[deisel]

Had Cable Drive Before, Cables Missing! Tachos Seized, Hence The Replacements, Did Try Connecting Both Positives, Havent Checked For Signal From W Terminal (Middle One) Will Do That Tommorrow Morning. Did However Try Both Tachos On Both Alternaters With No Joy. Both Alternators Were Replaced 1 Year Ago. /forums/images/graemlins/confused.gif

 

[chrismulli]

had a simular problem recently. in the end found that the tacho required to be simulated to work, something to do with the old wiring loom. way to test is use a power probe and while the engines running simulate the w terminal either at the altenator or the dial side from the supply. now to enable my to continue i have fitted a push button