Ever since I bought my 92 NA I have had the hard steering issue, alongside this has been the speedo & odometer occasionally just not working for short periods of time, initially I thought it was the speed sensor then I started to notice that it was usually when there was moisture around, i.e. after rain, but I have driven thru creeks where the water was up to say mid wheel and the speedo kept working so I figure I can rule out moisture underneath as a possible, anyway last week I changed the PSCU and low and behold my steering was back, Wow what a difference that made, anyway then we had a couple of days of light rain and the speedo went intermittent but was ok more than not but the Steering although not back to bloody hard as was certainly not working as it should have been, it seemed to be somewhere in the middle, today after a sunny day the steering is back to where it should be. So I am thinking that I have a dry joint in the cab somewhere probably in the cluster What's your thoughts?
Could also be your power steering rack is overdue for an overhaul, or the sensor there is one the way out/ dirty / shorting. Could also be a number of issues in relation to the suspension.
Bad joint in the cluster is a pretty likely diagnosis, somewhat common problem in Zs. If you google '300zx cluster repair' you should find some info on how to fix it up or you can just replace the cluster. The speed signal goes through the cluster to the ECU and steering control, sometimes the line in goes so you get no speedo or power steering, sometimes it's the line and the speedo is fine but no steering, yours may be both, or even a loose plug.
