Viva 1300 -75 temperature sender ohms

[VauxhallViva75]

Hi. When the viva came to me, it had aftermarket temp gauge. Original temp gauge does not move. Original gas meter works ok.

When I replaced fusebox, I noticed that pin E1 was damaged. And the wire to that pin is missing. Wire goes to the temp sender unit and from there it goes to the aftermarket meter.

So I routed new wire via new fusebox to E1. And from there to the temp gauge. Then I took the sensor wire off sensor and grounded it. Original temp gauge creeped to H. So i thought everything was fine and put the wire back to the sender unit.

However when i went to drive, temp does not rise on the original gauge, not even an inch or millimetre. After driving around, nothing. So i took the sender wire off and measured the ohms. Engine is about 50-60 C. Ohms say 680. After an hour ohms are at 800.

And still when I ground the wire, temp gauge moves to H. So is the temp sender unit faulty? Or the gauge?

Is there anywhere the correct ohm values for different temperatures?

EDIT: Sensor on my 75 viva is with the stump connector, not the Abiko connector (square). I believe that means it is the SU22 7966443 sender unit then?

[Fred Dukes]

grounding the wire which goes to the sensor give the correct result for the gauge - goes to full deflection as you said so it sounds like the temperature sensor has failed.

[1972nail]

As Fred says the sender seems to be the fault. I would also try grounding the brass external part of the sender to see if it makes any difference. There may be a bad connection from the sender to the head.

Also, there may be a thick coating of hard sediment around the wet end of the sender causing it to be insulated from the heat of the water.