temp gauge

hi all, all of a sudden my temp gauge as stopped working is there a common cause for this? i have just had the hg done so i would like to know its not getting too hot. it was working fine until this morning. k series

If the MIL light is on aswell the temperature sensor is bust.
Maybe the guage has just broken, try banging it to see if it frees the needle.

rang the dealer about temp sensor and was told there were 2 a brown 1 and a blue 1 changed the brown 1 the fan is not kicking in unless i unplug the sensor. should both sensor plugs have 2 wires running to them? i dont know if it as snapped but the blue 1 only as 1 wire the temp gauge as moved slightly but nowhere near where it should be. i am now running it with the sensor plug off so the fan is always on, is this a bad thing to do?

juleshs said:

rang the dealer about temp sensor and was told there were 2 a brown 1 and a blue 1 changed the brown 1 the fan is not kicking in unless i unplug the sensor. should both sensor plugs have 2 wires running to them? i dont know if it as snapped but the blue 1 only as 1 wire the temp gauge as moved slightly but nowhere near where it should be. i am now running it with the sensor plug off so the fan is always on, is this a bad thing to do?

Click to expand...

The blue one is for the dash temp gauge, check the connection.

Brown controls ECU, ignition/fueling, it is this one that kicks the fans in if unplugged

cheers for that. should the blue one have 2 wires to it?

Only one on mine, green wire

i had the auto electrician as been today says eveything is working fine gauge/sensor wise. however because my coolant is not cuuculating at all so the sensors are not getting hot enough. next question for you all is: could this be a shafted new thermostat or more likely the pump if the later is there any way to check it without stripping it all down??

Before we end up going round the houses, take back to the garage that fixed it and get them to sort it.

In hgf, sensors are not normally changed, so why did they change them?


If the coolant was not circulating then the engine would overheat and the fans would be on.

Stat could be stuck open or removed! In which case it would idle high over 1000rpm for a long time before warm up

i did the hg with a mechanic friend, the car as been spot on for over a week. i changed the sensor because the fan stopped working
i have changed thermostat 2nd 1 in 2 week bled the system and its still the same. tried it without thermostat and it as started to trickle back into the expantion tank, should it be a pretty steady flow without thermost (mine is a very light tickle) could it be water pump? it doesnt seem to be losing any water so hopefully my brand new head gasket is still ok. still no fan kicking in and temp gauge move about 5mm off bottom. i here there is a valve in the inlet manifold that get blocked, where exactly is it? any other suggestions to my problem will be graetfullly received HELLLLLPPPPPP

Hi Juleshs,
I have a 98' Rover 400 - same 16V K series that has also recently recovered from HGF.
My temp gauge also stopped working after the HGF repair - sound familiar?
The brown sensor is for ecu (2 wires - brown top) the other (one wire - blue/black top?) is just for the temp gauge.
This you already know from the 1.8 FL crew.

When I was changing my HG I must have knocked my sensors - both u/s so I changed them, the brown one worked - fans etc. came back correctly ok.
The other one - the (not-so-universal) blue one did not fix the gauge - I checked out the gauge with a variable resistor as in the Rover Rave and gauge worked ok within spec (cold >90ohm to <10 ohm hot range).
Checked out the new blue sensor in a saucepan and it operated over a completely different range (cold >600ohm to 100ohm hot range - from memory) even when hot the gauge would hardly move from its stop.
Took it back to main dealer who exchanged but new one - tested identical?

Seems they must have changed the gauge and sensor set at some point and now only supply the new range parts - main dealer could find nothing about a change tho' he did try to find out?
Check out your gauge with a variable resistor connected between the single wire and engine block to to find it's range and then check the sensor value between the terminal and body in a pan of hot water. If they match - you have another circulatory problem?

Fixed mine by going to a scrappy and finding a working sensor of the correct sort (happened to be a very old black one).
One tip is to check the used/old sensor in situ with an ohm meter and try to rotate the top insulator - I found many scrappy sensors are loose and intermittent, if you see one that changes value as you press on it or twists/moves - walk away it will be corroded inside and erratic at best.

I disected my old one and it was rusty inside even tho' it was not loose and had been reliable right up to my HGF work.
Hope this gives you some ideas for eliminating the electricals from the problem. :confused2:

The little 'jiggle ' valve is a small brass tube at the LH end of the plastic inlet manifold that has a small ball bearing inside the tube that can become stuck. It's purpose is to let air eascape back to the expansion bottle as I undestand. Lots of the Rover crowd suggest removing the ball and leaving the tube open. I did this when I did my HGF and it seems to have helped the circulation of the coolant around the system via the expansion tank so far. Temperature gauge now rises to a steady just below half way point and does not move other than down slightly at high speeds.

thanks for the info but im not good at all with all these figures i just like to plug and play, im only a mere joiner. i have sorted my cuculation problem but i still have no fan kicking in so im having to drive with the fan constantly on. would the temp gauge sensor in any way effect the fans coming on? i know they work off different sensors but just wondered if one could cause the other to fail?

The fans don't come on, hardly ever need to in the k-series that is working well.

I'd leave the jiggle as it is, it works fine and only under pressure

Are you getting heat from the cabin heater within 1-2min of startup from cold?

Td John has given you pointers,

Black sensor - YCB100370
Blue sensor -YCB100420/ GTR270/ GTR 317

They are NEG TEMP coefficient, resistance decreases as temp increases.

Values I have from mgfcar German site

142 ohms - 56 deg, needle at bottom
49-98 ohms - 65-85 deg, gauge 1/3 way
24.6-32.1 ohms - 100-110 deg, 1/2 way
16.9 ohms 125 deg - red zone

Plug the brown one back in and let it run properly

Hi NI, :5bcheers2:
Just had a quick check on the so called 'Universal' Blue (gauge) sensor I was supplied by the main dealer (still new in it's box).
Mine's Coded GTR316 - genuine Rover Unipart.
Measures 680ohms at room temp (~25*C) and drops to around ~100 ohm in boiling water. (result - my temp gauge barely moved when lump got up to normal temp)

From your fig's it looks like the FL gauge is nearer my Original Rover one but still using a slightly higer resistance for the hot end.
So a FL gauge won't work on a GTR316 - never gets hot enough to make the needle move up far enough! (sound familiar juleshs? have you got the right blue sensor?) :confused2:
As the FL setup is also very low resistance for the hot end, any problems with damaged wires or contact corrosion will make the temperature 'sensor-wiring-gauge' system read low. Really good design that!!
I confirm that the fans rarely come on when the water circulations in the K series is ok. So don't worry too much at this point, it's much more relevant that the radiator hoses get warm (top hotter than the bottom) and the heater pumps out heat, than the lump getting hot enough for the fans to kick in regularly (bad thing). :biggrin1:

Two sensor (blue & brown) systems are completely separate. The fans (controlled by the ECU) and gauge (just a piece of wire) are totally separate and do not interact in any way.

Maybe this is good info for anyone sourcing a replacement gauge from the scrappy - as long as they match the sensor range to the gauge range there are other options than the genuine parts?

Good nugget of info TD John,

Those figures are from the German Mgfcar site, which is a fairly accurate source used in MG Rover circles, only because of their German efficiency have they taken the time to catalogue the info in one place.

LR ones will be straight from MG/rover stock, I'd imagine the same range of values.

All the K-series should have the coolant running at around 88-90 deg so not sure what the application is for this GTR316 sensor. It wouldnt be the first time Rover parts have been labelled wrongly or batch is manufactured wrongly.

Put new sensor on mine fans and gauge still don't seem to be working, also keeps going sluggish when low on fuel no visible signs of water in engine