Water temp gauge

[DamianS3]

Hello

I think mine is caput, I'm going to check more tomorrow but it flickered to zero a little recently now just stays there.. I swapped sensor just in case but still nothing.

So anyone got a working example the would part with.. I'm thinking you Mike (Philpot) ?

Also feed to sensor was just over 6v where I would have expected 12v does this point to gauge failure or am I misunderstanding how it works.?

Thanks

Damian

[phillpot]

DamianS3 said:

.. I'm thinking you Mike (Phillpot) ?

Sorry, can't help with that one




I'd have thought there should be 12 volts at the sensor, are other gauges reading about right?

[TVRees]

Do you mean this one ? Here it says it operates at 5V at the sensor.

Did you measure the resistance of the sensor ? As it says, this should decrease as it gets warmer.

[GreenV8S]

I expect the sensor will be connected in series with a resistor to form a voltage divider. It may also have a resistor in parallel with it to get the desired voltage / temperature characteristics. I don't know what the normal voltage is but I'm not too surprised that it isn't seeing full battery voltage and I'd view anything over 0V as an encouraging sign. If you have another identical setup you could compare with that to see what's 'normal'. (I'm not volunteering to go out to measure mine.)

If you have any resistors available you could check that the gauge displays a sensible reading as the resistance changes over a range 1KOhm - 10KOhm. It should read hotter as the resistance goes down.

[phillpot]

GreenV8S said:

I'm not volunteering to go out to measure mine.

Wimp

happy to spend a few minutes with a meter on mine............... tomorrow.

[TVRees]

The 5V supply comes from the ECM/EEC.

Expect 4800 to 6600 Ω at 20 °C and 250-400 Ω at 80 °C.
So, voltage 3V cold and about 0.5V hot.

If it's not like this, then the engine may run abnormally when hot or cold.

[phillpot]

TVRees said:

The 5V supply comes from the ECM/EEC.

Expect 4800 to 6600 ? at 20 °C and 250-400 ? at 80 °C.
So, voltage 3V cold and about 0.5V hot.

If it's not like this, then the engine may run abnormally when hot or cold.

Ermm, isn't the gauge is totally independent/different circuit altogether from the ECU and its sender unit?

[TVRees]

Yes it is. I was referring to the sensor, not the gauge.

[tvrgit]

There are 2 separate sensors.

One sends a signal to the ecu, affects engine map etc as above. The other sensor only works the gauge. Which one are you testing?

[TVRees]

Yes, there are two. You are correct.
Sorry, I was going off in the wrong direction a little and was only referring to the ECM sensor.

[DamianS3]

Hello folks, quick update.. yes there are 2 sensors the ECU is happy that it knows the temp ok so no problems there, the ECU is also running the fans so another bonus.

It's the gauge sensor or gauge I have an issue with.. unfortunately I got rained off today so will whip the gauge out tomorrow and see what I can see.

Thanks for your help so far.. will report back.

Damian S3