Temperature Gauge

Hi all,

Seems to be one thing after another with with my P38, finally stopped it loosing coolant and thought that would be it for a little while but now the temperature gauge on the dash has stopped working so if it does overheat I wont know until it too late. so was wondering if any one here can help.

If I am reading things correctly its the temp sensor with the green plug that feeds info to the dash gauge, the sensor with the brown plug feeds the ECU and both are identical parts I believe.

When I click the ignition on all the warning lights come on as normal (and go off) and the gauge lifts as it always did to just below the blue mark. usually after a few minutes on the road would be raising to its 12 o'clock position, but now stays at the blue.


The wiring to the connector looks OK, I have tried popping the green connector on the ECU sensor as I beleave they are both the same sensor, in a hope that it would show a reading on the dash but the needle did not move.


any suggestions on where to start looking?

thermostat stuck open

Druim said:

thermostat stuck open

Click to expand...

not sure, does not even move on a long run, would have thought the V8 would need to get rid of as much heat as possible via rad. certainly wanted it when over flow was blocked.

gibby_wls said:

not sure, does not even move on a long run, would have thought the V8 would need to get rid of as much heat as possible via rad. certainly wanted it when over flow was blocked.

Click to expand...

have you checked? rad should only be warm after stat opens, no flow at cold start, easiest to feel the top hose or rad outlet
does fan work/stop when not needed?

Druim said:

have you checked? rad should only be warm after stat opens, no flow at cold start, easiest to feel the top hose or rad outlet
does fan work/stop when not needed?

Click to expand...

fan works fine, will double check the rad, will have to wait for it to cool down as its all red hot at the moment (hopefully without being too hot).

I would expect it to heat up to normal running temp after 40min trip home in Friday night traffic even with stat fully open.

Sounds very much like gauge sender,had exactly the same symptoms on mine.
Not sure if senders are the same,diesel has 3 all different colours,though if yours are both the same colour then perhaps.RAVE should tell you hopefully.

I have looked at RAVE and the comment in my post are from what I understand. but could be completely wrong

gibby_wls said:

fan works fine, will double check the rad, will have to wait for it to cool down as its all red hot at the moment (hopefully without being too hot).

I would expect it to heat up to normal running temp after 40min trip home in Friday night traffic even with stat fully open.

Click to expand...

When my stat failed, the gauge barely left blue when hottest

Mine started doing that after I fixed a coolant leak. In my case the rad had a small leak so I took no chances and put a new rad in. Ever since then it has stayed in the blue as opposed to sitting at 12 o'clock pre the new rad.

I have been on many long drives and the temp never shows much more than a needle width above blue. I presumed that the stat had jammed open, or at least partially open.

Opinions on here at the time said it was not a critical to run it like this.

I should probably look into it again but I would prefer it running cool than too hot.

Druim said:

When my stat failed, the gauge barely left blue when hottest

Click to expand...

its hardly getting into the blue, I am hoping not I don't want to have to change it again, only just stopped it loosing coolant and got all the air locks out.

gibby_wls said:

its hardly getting into the blue, I am hoping not I don't want to have to change it again, only just stopped it loosing coolant and got all the air locks out.

Click to expand...

mine was in the hot'ish summer, now it would possibly be lower

just thinking out loud, if I was to short across this pins of the connector with a wire should it send the into the red, proving that at least their is a connection to the dash?

gibby_wls said:

just thinking out loud, if I was to short across this pins of the connector with a wire should it send the into the red, proving that at least their is a connection to the dash?

Click to expand...

If the coefficient is anything like the one illustrated in this thread then I would imagine it should at least show an increased temp.
Need temp sender resistance values (Series 3) - Series Forum - LR4x4 - The Land Rover Forum

I know its a Series III but...... maybe it is the same/similar.

gibby_wls said:

just thinking out loud, if I was to short across this pins of the connector with a wire should it send the into the red, proving that at least their is a connection to the dash?

Click to expand...

i gave that a try ,but on mine the gauge still did not move but i got a "faulty temp gauge" message on the dash.Even tried it with a potentiometer across the pins,but a new sender fixed it in the end.

Buy a resistor between 25 & 50 ohms (for a petrol engine this will give a vertical needle position) and use it in place of the temp sensor. If you have a green temp sensor correct it between the 2 pins of the harness connector. If you have a single wire sensor connect the end of the resistor to the engine block.To check what the actual coolant temp is, buy a cheap infra red thermometer and check the engine block temperature next to the temp sensor. The coolant temp will be within a couple of degrees of the reading once engine block has warmed up.