Change to HE dashboard and installation of electric speedometer

Rationale

These two modifications were done together for reasons, to me. These were

1. A HE electronic speedometer was required (pre-HE are mechanical only)
2. The dash wiring loom was somewhat butchered, with home made fuse box.
   
3. The newer model dash with wood (elm?) inserts suited the tan interior better

This is the situation I inherited with the car. Starting afresh with an intact pre-HE dash harness would give me more confidence before adding a few new wires to drive the speedo. 

HE Dashboard Install

There are only 4 bolts holding the dashboard in place. To get to that stage, all you have to do is remove the steering wheel, instrument cluster, centre console, stereo panel, clock panel, ++, and disconnect all harnesses.

With another pre-HE harness it is straight forward to match the connectors (the HE harness has different connector plugs with different wiring, experience gained from my red car.) Some experimentation is required with the wire routing though. Some things are also a good idea "while you are there", a phrase that Jag owners know. Odd jobs like LED bulbs, and running a microphone for the stereo up near the rear view mirror. I added the power and signal cables needed for the speed sensor, converter, and signal (see below).

The dash condition was good but the wood inserts were cracked. I thought that I would try vinyl wrapping those, so that I could also match the stereo surround and centre console. The alloy parts were sanded clear, and the ashtray inserts on console levelled flat with some ply and filler. This was my first experience using vinyl wrap and I was pleased with the transformation and end result. (People think that it is all wood until I tell them.) I used a hot air gun and a scalpel set. The corners need to be cut/sectioned on back side, and edges folded in stages.  

The centre console was recovered in tan and got a matching manual gaiter. This first version is too tall. The chrome edge strip brings it back to the 70s a bit.

Other customisations include the DAB/Bluetooth stereo and a SAAS steering wheel reminding me of my early driving days.

Electric Speedo Conversion

Speed transducer

The Toyota part number for the Supra gearbox is 83181-20040. Be mindful not to lose the separate connector shaft.

I had to experiment to match the wiring to the plug so here is the good guts.

• Pin 1 (Yellow): 12V
• Pin 2 (Red): GND
• Pin 3 (Yellow): Signal

Once tested the wires will be routed down past the shifter to the gearbox and the plug reconnected; I wont be making another hole big enough for that to pass through.

Signal Converter

This box is where the magic happens. Earlier experiments on Jaycar provided versions would not work. The converter that worked for me is the SGI-5E. 

This unit can perform several types of transformation and the settings that worked for me are as follows:

The little yellow wire

The circuit diagram to connect these parts looks like this.

All of this effort is to feed the correct signal into the electronic speedo which is an additional yellow wire on one of the cluster connections. I inserted another pin into the dash connectors, taped it into the cluster, and made a separate connection to the back of the gauge (not via the plastic circuit board).

The wiring is installed so that there is length for the passenger to hold the signal converter and calibrate up/down, to be later tucked up under the dash. Passengers sit on the left in our great land.

Commissioning

Before installing the transducer onto the gearbox, do an integration test with the system in the car, using a power drill to check for needle movement.