How does the low coolant level sensor work??

[92rrrandall]

Have a 1981 TR8. How does the low coolant level sensor work?? I assume 12v is applied when the ignition is on, and there is a switch inside the metal resivoir which grounds the circuit when the level drops. Can not see inside the tank.

Would like to custom make my own overflow tank/air seperator. Need to figure out the best way to incorparate a low coolant sensor.

Randall

[Odd]

No switch in there...
It's just an isolated spigot that goes into the water and grounds the detection cirquit via the cooling fluid.
When/If the level drops below the spigot the electronics in the little plastic tube lights the warning light.
The reservoir itself is isolated from the car via the rubber strips and the rubber hoses so the only route to
ground is via the fluid itself.

Istr reading somewhere a long time ago that there is supposed to be some resistance in the water circuit
and the electronics in the plastic tube might be harmed if you ground it directly to chassis ground.
But as I said it's a faint memory...

[lebochet9]

Once you have checked the wire for continuity and that the bulb in the dash is working fine, move on to the sensor circuit which is housed in a grey or black plastic tube hidden under the dash. The tube is about 3-4" long and under 1" in dia from memory and has a multi plug in it. It is friction welded shut, but can be opened with deft use of a dremel. There is a small PCB inside with an IC that normally blows. I bought a similar one from Maplins an replaced it, along with, also from memory, a resistor. There was a Circuit diagram somewhere on the web explaining how to do it.

1980 DHC TR7-V8 (was an 8V, then a Sprint)
Back on the road after 3 years restoring...