Temp gauge not working

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Aussiecsi

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Guys, until recently, the temp gauge on my csi seemed to be working but now seems to have stopped .

When the key is turned on ( prior to starting engine ) , the temp gauge needle will flick slightly about 1 to 2 mm and that's about it . It doesn't move even when engine is hot .

My "gut" instinct is that it might be a grounding issue but not sure where to start ...tried alternative temp sender and no change . Help please . Thanks , Simon
 
If memory serves, you just touch the sender lead direct to earth. The guage should show max deflection. If it does the sensor is at fault, if nothing happens its the feed to the guage.
 
The gauge reflects voltage in the circuit. The sender is a variable ground. The sender is designed to vary the ground in the circuit; when the engine is cold the sender allows very little voltage to flow; as the engine warms to normal operating temperature, the sender provides a better ground, allowing an amount of current flow that enables the gauge to show the needle at 3 o'clock. If the temp rises above normal operating range the sender allows a full current flow and the needle on the gauge goes to max deflection.

This is why the gauge will show max deflection if you touch the sender wire to earth. If you don't get max deflection, which you may not because you have already tried more than one sender, you may have corrosion in the wiring, or perhaps a broken wire, somewhere in the circuit.

Given that you have access to the back of the gauge, I suggest two tests. First, disconnect the sender wire from the gauge and check the continuity of this wire. If this is ok, disconnect the power wire to the gauge and measure the voltage to the gauge (with the ignition switch on). If you don't have twelve volts, then you need to check the continuity of this wire. We can help you find the other end of this wire if you provide more info on your car.
 
Well gents , just to wrap this up ; did the various tests but the "red herring " was using a sender that was known to work on another car but didn't work on mine . So, today , while doing other bits and pieces, our Forum friend Wally suggested he substitute his sender for a "second opinion "...yes, the gauge worked !

The vagaries of these mistresses continues . Thanks again for your input . Cheers, Simon
 
Hi Simon -- You don't need to seek out a sender that is specific to our cars. I last year replaced mine with the VDO aftermarket sending unit, and it works fine. I don't recall whether it is a 12 or 14 mm opening (VDO makes two of them), but you should be able to just measure the thread on the unit you have that doesn't work.
 
Ohmess said:
Hi Simon -- You don't need to seek out a sender that is specific to our cars. I last year replaced mine with the VDO aftermarket sending unit, and it works fine. I don't recall whether it is a 12 or 14 mm opening (VDO makes two of them), but you should be able to just measure the thread on the unit you have that doesn't work.
Click to expand...

Thanks Chris, ended up adding new sender to Walloths order but good to know it's generic. Cheers, Simon
 
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