[alanmay0]

Hello I have a 1967 GTO with the gauges in the dash. I am currently taking the dash out to clean the gauges and replace the gauge lens. I don't thing my water temp gauge works. So I need to know what is the resistance in ohms for the sending unit is so that I can check mine. Of course any suggestions on how to check the oil temp sending unit and gauge along with checking the water temp sending and gauge would be appreciated. I have the actual gauges not the idiot lighs.
thanks
alan

[gtospieg]

Contact Pete Serio on here...he rebuilds these and I'm sure he knows the answer to your questions.

[25stevem]

Take your cars battery or your charger if you have one and hook it to the terminals on each gauge.

If the gauge is good it will peg itself.
You could use a 9 volt lantern battery for this test also .

You may even be able to use a common 9 volt battery .

I have never tried this out, but it may have just enough current such that you could atleast see the needle on the gauge jump up a tad which would confirm that it’s not a open circuit.

The way they work is that power first goes to the gauge, and when the sender is cold it’s resistance is very high so no current can flow from the gauge to ground , ground being the motor.

As the sender warms up the resistance starts to drop , current then flows to ground and the meter needle goes up.

This is how the temp gauge works, the oil pressure sender is a tad different.

In this sender the resistance amount is not change by temp.
This resistance is changed by the oil pressure itself.
In a way this is the same thing that takes place when you turn up the volume on your cars radio volume knob ( analog audio wise) in this case the action of your fingers moving the knob changes the resistance/ current flow, and in the pressure sender it’s the oil pressure.

Note that since these run on DC voltage if you hook them up reverse the meter needle will go down and not up, and this action you may not see.

[70GS455]

The oil pressure sender will read 0 ohms at 0 psi and 90 ohms at max psi.

The water temp sender will read 1200 ohms cold and about 90 ohms hot.

Hook those equivalent resistances up to the sender connections and see what the gauge reads.

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