Datsun Roadster Forum-311s.org

So I’ve finally had my radiator recored after trying and failing to buy an aluminum one online (3times!). Filled it up and ran it, but noticed my temp gauge isn’t moving. The other gauges on the cluster seem fine. I checked voltage at the sensor wire with key on, and it pulses from 9V to 0v every second. Is this normal ? I don’t want to run the motor without knowing engine temp. Any thoughts out there on this ? Thanks.

Ground the wire ...it should quickly peg the guage
You can test with ohms too
Did you use a fill funnel to be sure it's full

I did not use a funnel. Just a hose into the fill neck. Than halfway in the overflow tank as well. What’s the purpose of a funnel ?

I assume you have a 1600. Filling the cooling system via the cap on top of the thermostat does not fill the top tank on the radiator. Some folks use a funnel onto the small hose to the radiator by removing it from the thermostat. I prefer to disconnect the upper radiator hose from the engine & fill the radiator that way. You may need to tape yup the radiator hose fitting on the thermostat if you get a lot of water coming out there.

Pulsing voltage on the hot lead to the temperature gauge & fuel gauge is normal.

Possible silly question but are you filling it with the garden hose then a coolant concentrate or 50/50 mix the entire fill cycle?

RussellC wrote: Thu Jun 17, 2021 3:00 pm Possible silly question but are you filling it with the garden hose then a coolant concentrate or 50/50 mix the entire fill cycle?

garden hose is going to leave minerals and crap in your radiator and engine. use distilled.

1970 SRL311. I didn't know that filling from the cap on the filler tube was incorrect. I plan on doing a 50/50 mixture.

jayedeluxe wrote: Thu Jun 17, 2021 4:03 pm 1970 SRL311. I didn't know that filling from the cap on the filler tube was incorrect. I plan on doing a 50/50 mixture.

Someone thought your car was a 1600. I think you are good.

I always just use my fill tank funnel to assure it is completely full, air bubbles will stop it flowing ...certain cases, heater core

As mentioned, my guess is that you have lost the ground connection to the stat. The stock gaskets have a metal tang in them that grounds the unit. This can fail. I have decided to run a ground wire that wraps bare wire around the outside of the sleeve that the sensor slides into and connects to one of the mounting bolts to ensure a good ground.

"I checked voltage at the sensor wire with key on, and it pulses from 9V to 0v every second."

This is normal. The instrument panel uses a voltage regulator which decreases the voltage from 12V to 8 - 9V.