Testing Rev Counter/Tachometer - How?

[Richard10002]

Before I spend £220 on a new rev counter:

In another thread AlanB and someone else provided a method of testing my rev counter with a 12v supply, and a 9v supply. I just want to confirm exactly how to do it:

Here is the back of the rev counter VP Part No. 873688 VDO No. N 02 070 109

There are 4 connections inside the "plug hole" where the top two are marked left - S+ and right S- . The bottom two are marked left + and right - . The connector to the right of the plughole has no markings, but had a red wire connected to it, (I wonder if this is for the hour meter.

My understanding was that I connect the 12V supply to the bottom + and - terminals, (does polarity matter?). I then connect one wire from the 9V supply to S+, and pulse the other wire from the 9v supply "where" ?

I've got 6 second hand rev counters and pulsing the 9v wire on S- had no effect on the 2 I have tried. It's obviously possible that they are all not working - hence the question.

Many Thanks

Richard

 

[Refueler]

Better to spend a couple of quid on something like this ...

Hand Held Tacho

I bought one ... told another guy - he bought one and before I tested mine confirmed it was spot on !

It's quick inexpensive way to verify readings. No use to check the Rev counter for why not working ... but once you have one reading something - this will calibrate.

 

[Heckler]

Richard
as i understand it the 8v is AC and it needs this to work, if you want to meet me in pwllheli you can do a straight swop in my panel to check them to see if they are working or not
Stu

 

[earlybird]

How are you pulsing the 8 or 9 volts? The tacho works by measuring the AC frequency output of the alternator. Just to move the needle off zero is likely to need a maintained frequency of several tens of pulses per second.