I have a Jap TT where power steering not working nor speedo. Jeff Turner fixed this issue around 18 months ago by adding a new wire from the back of the speedo cluster down to a connector in driver's foot well.

 

The fault came back some months later.

 

Another issue, when I got the car home from when Jeff first fixed it, I noticed the boost gauge was pinned at max and that some of the back-lighting wasn't working. I never got the chance to take it back to Jeff prior to his finishing.

 

I took the Jap cluster apart today and re-soldered all the joints to the chip and the rest (electronics is what I do) but no joy.

 

I had another UK cluster which Jeff let me have and tried that today as well but no joy, again the boost gauge is pinned at max.

 

There are obviously several issues here.

 

Any suggestions as to pin-pointing this and a way forward etc?

 

I noticed the wires/insulation on the plugs to the cluster are somewhat 'crsipy' and fragile!

 

Any help greatly appreciated, tnx!

What happens if you disconnect that extra/new wire that you mention?

Sorry for not explaining, the signal from the speedo system that sets the stiffness of power steering, wasn't there according to the diagnostics on Jeff's laptop. (without it, system defaults to stiffest setting for higher speed driving etc as safety default, according to Jeff)

 

The new wire, remade the lost connection allowing the system to alter the power steering stiffness according to speed. It seems there was a break in that wire somewhere between the binnacle and the connector in the foot well.

 

Without it connected now, no change.

Ok, so if I understand correctly both speedo and signal from speedo (to HICAS ECU, which controls the powersteering) were fixed, otherwise the heavy power steering problem would have still been there.

 

Now speedo (signal) has gone again even with another cluster.

In that case I would have a look or replace the speedsensor (in the gearbox) or trace/check the signalwire from the speedsensor to the speedo.

 

The boostgauge pinned to the right could be a disconnected or faulty boostsensor (under the bonnet) or also a broken wire at the back of the cluster

 

this may help to trace/find the wires you need:

http://300zx-twinturbo.com/cgi-bin/manual.cgi?list=el&dir=&config=&refresh=&direction=forward&scale=0&cycle=off&slide=66&design=default&total=133

Ok, so if I understand correctly both speedo and signal from speedo (to HICAS ECU, which controls the powersteering) were fixed, otherwise the heavy power steering problem would have still been there.

 

Now speedo (signal) has gone again even with another cluster.

In that case I would have a look or replace the speedsensor (in the gearbox) or trace/check the signalwire from the speedsensor to the speedo.

 

The boostgauge pinned to the right could be a disconnected or faulty boostsensor (under the bonnet) or also a broken wire at the back of the cluster

 

this may help to trace/find the wires you need:

http://300zx-twinturbo.com/cgi-bin/manual.cgi?list=el&dir=&config=&refresh=&direction=forward&scale=0&cycle=off&slide=66&design=default&total=133

 

Big tnx for your suggestions, the wires look favourites to check first.

 

I'm not big into car electrics, a different world to audio electronics somehow!

 

Since there are a number of isolated diagrams it doesn't, for me, seem straightforward to understand what to expect on each connector terminal.

 

Possibly more so with the 300 as I understand that many things are at +VE potential and earthed to turn them on.