Mk1 Digi Dash - Boost Gauge Mod

Evening all

After successfully getting the boost gauge on my mk1 digi dash up and running I thought I'd knock up a 'How To' on how I did it in case anyone else is looking to do the same.

Firstly, the signal to drive the little bargraph boost gauge is outputted by the Microplex ECU on pin 23. Usefully, the pin is already connected in the main connector block via a light green cable, as shown in the below picture:



Note: the wiring diagram in the Haynes manual incorrectly shows this cable as being coloured "SN" i.e. pink/black.

Tracing this cable through the loom it ends up within the 3-way spade connector block that connects the ignition loom to the main loom (somewhere behind the battery tray towards the back of the engine bay), as in the below picture:



On a non-Digi-dash car this cable terminates within the 3-way connector block - on the picture above all 3 pins/holes are occupied going in (from the right) but only 2 on the other side are, with the empty hole on the female side being the one you're after to connect to. In my case I was reworking the entire loom anyway and while doing so I added a female spade terminal (with latch) with a length of green cable to run on within the main loom, through the bulkhead and onwards to the back of the digi dash.

Once there the cable needs to be connected to the tab highlighted in green on the below picture:



To do mine I extracted one of the right-angled copper terminals from a spare electric window loom I had so that I could connect to the tab 'properly' and within the original multi connector. There is also a gnd connection that needs to be made, without which the digi-dash won't work at all, to the tab highlighted in black in the above picture.

And that's it - having connected as per the above your boost gauge should work!

Very nicely done mate and are first "how to guide"  

excellant guide

Top work, thanks for making it so clear and solving the mystery of the digi dash boost gauge after all these years"

Glad to help solve this mystery. In a way it's fitting that I sorted this on my new Uno as I retro-fitted the digi-dash to my original one back in the late 90's but never had the boost gauge working. I remember thinking "there must be a wire from the ecu that needs to be connected to the back of the digi-dash" but never got around to trying to identify it and the car was 'retired' without me having sussed it. All these years later I almost got emotional when I finally had it working!