Digital Dahs

what else on the dash is not working? is anything intermittant or cutting in and out? You probably have a bad power supply. This can be remedied by sending the unit into Xenonzcar.com for soder repair.
the speedometer on the digi dash is controlled by the speedo sensor located on the passenger side of the engine bay next to the battery. the boost sensor controlls your RPM meter and is located on the drivers side close to the coil and vacuum pack. both of these are availabe from Steve B over at http://www.300zxpartsforyou.com/ these are used parts, but they are cleaned and tested and in working condition. I had to replace both of these units on my 87 and they worked just fine. the gas gauge i'm not so sure about, but you would probably benefit by getting the power supply done. I had to have it done on the dash display in my 84 and now it works great.

cheers,

Bon

like I said, your cars speedo sensor is not working. when it just sits at zero like that, the sensor has failed. you can't get these new, but you can get one used from the above website.

your gas tank sensor could be bad. i've never dealt with this part before, but I believe its in the tank and you can access it from the hatch area without removing the tank. that could be causing the problem.

You pretty much just have to roll with the used parts, man, sorry…

I've gone through 3 speed sensors to get a good one. Unfortunately, that's our lot in car repair life. I haven't figured out how to take apart the speed sensor without damaging the underlying circuit board. (yet)

yes. you did state that. and you also said that you couldn't find parts used that are guarenteed to work and then you asked what guys have done to fix these issues. everyone here has answered your original post, including me. twice.

again, here are your options: you can get the sensors you need from a parts car, you can buy them used from the reliable source website that i have already mentioned, you can swap your digital display unit for an analog one, or you can just not buy any used parts and continue to drive at 0 and empty.
dude, your car is 30 years old. a lot of factory parts are not available anymore and like the rest of us, you have to deal with what IS still available.

better to have a working used part than an original part that doesn't work at all.

Bon

I once had to replace my speed sensor (digi dash) , but it turned out…
it was just the +12v wire that wasn't working on the sensor harness
turns out something behind the dash drives this voltage, I ended up rewiring it to one of the relays that switches on with the car.

So you may have an issue I ran into with the gas gauge, the bulbs behind the dash burned out! Sucked I drove around for 2 years with no gas gauge. These are not simple bulbs to replace, so I ended up with my mechanic that does tons of Z work taking mine out and buying a refurbished one. Not sure where the heck he got it, but the recommention about for Steve's site is your best bet. He tests all the parts. You may also be able to remove the dash (not trivial) and send to a repair place, but sounds like a few issues your having. The gas part is probably bulbs, the speedo are the parts referenced above. There are no parts left for our cars at the Nissan Dealership sadly.

Not quite true.... you can still get the brake light/clutch rubber bumpers.

LOL, that is funny. Last time I needed an alterator they had one but that was a long time ago. I bought out the last of the interior plastic color coodinated parts about 18 years ago from the local parts counter…Steve is huge for this type of stuff now.

All the plastic parts are NLA? Sad, a new era

Been gone for MANY years, Steve's website mentioned above is where I have bought all the parts in the last 15 years unforunately. Heck you cannot buy an Alternator anymore barely never mind a color coodinated plastic piece for interior

i'm glad Steve B does what he does. i don't know where my Z31's would be without him. but it is sad that we can no longer get basic interior parts. although i actually have pretty good luck getting parts from nissanpartsdeal. they still have a lot of stuff available. i managed to get several interior rubber pieces and other hard to find parts from them.

whenever something breaks on the Z, its almost always a part that is NLA and i go right to 300zxpartsforyou.com. Steve to the rescue. even if the part is used, better to have a working used part than a part that doesn't work at all.

Bon

Shoot-- I bought a reman alternator in 2010 from autozone. Had them bench test it before I left the store-- it was a dud. None left in stock. Went across the street to O'reilleys (sp) and had them price match on a good one.

My car is heading for its 10 year timing belt replacement next month and I am thinking of replacing my alternator even though it is still working fine, Z-Expert in Los Angeles still has some Nissan OEM ones that he bought years ago....I have my back-light dash gremlin and gas tank sensor being replaced along with new timing belt, cam seals, water pump, hoses etc being replaced on a 10 year cycle.