Datsun Roadster Forum-311s.org

I have installed a new temp sending unit twice now, tested my temp gauge ensuring that it works and I still do not get a temp reading. I have heard stories of fixing a ground and or a different sending unit??? not sure what to do.

I pulled the wire going to the temp sending unit and attached it to the battery and the gauge works fine.

anyone had this experience? know how to fix?

Is it a U20 engine?
You need an earth supplied to the sender housing since it can get insulated from the engine and thus ground, by the housing gaskets.
Use a multi meter and check the continuity of the housing to a good ground.
My best guess is there won't be any continuity.
Simplest fix is to add a ground wire.
Attach it to the sender housing, e.g. the sensor itself, and fix the other end to a good ground point on the engine.

Also are the rest of your gauges working properly? If not, suspect the gauge voltage regulator. My bet is on the ground.

I run a ground wire off the outlet. You can just see it in the pic


I ran it down to the frame where the main battery ground is.

Will

"I pulled the wire going to the temp sending unit and attached it to the battery and the gauge works fine."

I'll take that to mean the temp gauge pegged. Therefore there are only two possibilities, the senders are bad or not grounded properly.

I did like Wil, 'cept the pass side alt base is my main ground junction for frame-to-block, frame to alt, so the wire is a real short U-turn.

the original thermostat housing gaskets come with a small copper tab that grounds the sending unit and completes the circuit. I have these in stock. If your fuel gauge is also acting up, it could be the small voltage regulator under the dash by the steering column.

Ross
sports imports

Ross, do you carry the small VR under the dash? I tried the aftermarket one for the 510 I think. It gets hot. My stock one works ok, but my gauges move around sometimes.

I use a small wire and ground it to the back of the alternator.Just need to drill / tap the plug, and add a mounting stud to attach the ground wire.

Arnold

When I make my gaskets I punch a very small hole in them and install my own grounding staple made out of copper wire, then make sure we have a good clean surface with no gasket sealer in that spot... has worked 3 times.

Nissanman wrote:Is it a U20 engine?
You need an earth supplied to the sender housing since it can get insulated from the engine and thus ground, by the housing gaskets.
Use a multi meter and check the continuity of the housing to a good ground.
My best guess is there won't be any continuity.
Simplest fix is to add a ground wire.
Attach it to the sender housing, e.g. the sensor itself, and fix the other end to a good ground point on the engine.

yes its the U20. I will try this!

notoptoy wrote:Also are the rest of your gauges working properly? If not, suspect the gauge voltage regulator. My bet is on the ground.

Yeah they work and I just replaced the voltage regulator in the engine compartment. does the car have a separate regulator for the gauges?

sports imports wrote:the original thermostat housing gaskets come with a small copper tab that grounds the sending unit and completes the circuit. I have these in stock. If your fuel gauge is also acting up, it could be the small voltage regulator under the dash by the steering column.

Ross
sports imports

oh ok gotcha! do you also carry the second gauge voltage regulator?

Thanks!

Yes. It is located near the steering column, under the dash.
If the fuel gauge behaves normally at the moment, leave the instrument VR alone for the time being.
Just temporarily ground the Temp sender sensor plate at the engine and see if that solves the initial problem.

my 1600s temp gauge stopped working,there is a yellow wire attached a the base of the cooling tower just below thr small cooling hose going to the carbs. all other gauges working the wire is connected to the block by an eye hook i believe. should i test the wire the same way by running a wire from the battery?