How To Test The Rev Counter?

[pip470 61]

Ok I have a gti-6 running on mbe ignition only ecu. There is a take off from the ecu that you connect to the rev counter.

 

On my drag car this connected to the halfords rev counter and worked fine.

 

the same halfords gauge worked fine being connected to wire 112 from the back of the rev counter when fitted to one of my old gti's.

 

So my thinking is that the rev counter on the standard cluster should work if I connect the output from the ecu to 112.

It doesn't.

 

So How exactly could i test he rev counter to see if it works. I thought I would be able to put a direct live feed to wire 112 and imagined it would go to full deflection on the gauge. It didn't do anything.

So can any one help?

[petert 588]

This has been well discussed in the ECU section, but I'll do it again. There is a large resistor and capacitor which filters out small input signals (12V). The tacho is thus looking for the large back emf (approx. 400V) generated when the coil collapses. To test, you could take the cluster out and try connecting 112 and +12V to another coil/car.

 

Remove (or bridge) the resistor/capacitor and it will probably work fine for you.

Edited March 10, 2009 by petert

[pip470 61]

This has been well discussed in the ECU section, but I'll do it again. There is a large resistor and capacitor which filters out small input signals (12V). The tacho is thus looking for the large back emf (approx. 400V) generated when the coil collapses. To test, you could take the cluster out and try connecting 112 and +12V to another coil/car.

 

Remove (or bridge) the resistor/capacitor and it will probably work fine for you.

 

 

Thanks for that petert, I was aware that there was some kind of mods that could be done but wasn't sure if this was because of the 4 coils instead of the one. After loads of reading after you're promt I carried the mod out and the rev counter now works. I have no idea how accurate it is yet but i hope the rolling road on friday can give me some clue. Thank you very Much.

Phill