How to enable the stock shiftlight in your tach

[Elv15]

I have a 2003 Caterham with the std gauges. If you look closely, you will see that there is a big LED in the middle of the tach. Well guess what, that's a shift light. Unfortunatly, it is not really useable in its current form as it is always on! I designed a small circuit to invert it's behavior and now have a working shift light.

FYI, the original thread is here: http://www.blatchat.com/t.asp?Id=89522

Here is the schematic:

[Boxologist]

this will work from the 'stock' ecu or will this only be enable from an aftermarket ECU?

[Elv15]

stock ecu

I'm not sure about it working with the "stock" ECU. All that it really needs is an ECU that has a grounding shift light control. I would be suprised if any of the stock ECU's had this functionality (does the focus have a shift light?). Also you would probably want a way to set the rpm at which it turned on.

Sorry, I'm not too familiar with the stock ECUs out there...

[slomove]

At least I can say the circuit would work with the Emerald just the same way. What I don't understand with it is that the voltage of the LED should be still about 4.8V when the transistor is turned fully on [12V * 1k / (1k + 1.5k)]. So it would never turn off, just get a little dim....or am I missing something ? But maybe there are more than one LED in series and the 4.8 V is not enough to turn on?

Gert