I have a Felicia 1.3 lxi from 1995. My problem is that the coolant temperature gauge moves to maximum almost immediately after starting (within half a minute).

I have had the problem for awhile, so as an intermediate solution, I have connected the temperature sensor to an ohm-meter (is that the right english word???). I now read the resistance as it changes while the engine gets hotter. I also made a diagram relating the heat of the coolant to the resistance (using a hot-water bath).

The point is that the engine has the correct temperature.

I have tried changing the instrument panel with no succes. I also changed the sensor with no succes.

Any ideas what to do next?

Stefan, Denmark

Check the wire for any breaks in the insulation, if you connect the wire straight to earth the gauge will go to the maximum.

...and by the way, welcome among the Vikings of Briskoda, Stefan!

Check the wire for any breaks in the insulation, if you connect the wire straight to earth the gauge will go to the maximum.

:iagree: - and I may be "teaching my grandmother to suck eggs" as the saying goes, but the temperature guage almost certainly is a voltmeter, just with a scale calibrated in degrees rather than volts.

Does that mean it works in reverse? A short would surely mean 0v and therefore a low reading? But then again resistance increases with temperature, doesn't it?

thank you for the welcome and the reply. I will check it out and let you know.

With regards to:

Does that mean it works in reverse? A short would surely mean 0v and therefore a low reading? But then again resistance increases with temperature, doesn't it?

The resistance decreases with increasing temperature. At least in this sensor.

The resistance decreases with increasing temperature. At least in this sensor.

Oh yeah! What I put would appear to only apply to power resistors!

Try running a new wire from the back of the guage to the sensor & tape it to the existing loom - remember to disconnect the old wire or the problem will persist.

(Edit) Temp guage circuits have a direct 12v feed to the meter (0v when the ignition is off) and an earth through the sensor (hence one wire) which is a temperature sensitive variable resistor. An open circuit from the guage to the sensor will give a "Cold" reading and a short to earth before the sensor will give a "Hot" reading. The hotter the engine, the less resistance through the sender.

The time delay between starting your motor & the guage going hot is a bit of a mystery though.