Unknown Engine Temp

[mgf15]

Hi All, since buying my 97' MGF, I've found the engine temp gauge reads real low (barely moves) but occasionally does go up to about 1/4, then seems to drop again. I removed the sensor wire and grounded it out with the IGN on and the gauge moves full scale. So I assume the gauge is functioning normal. I assumed the sensor was the issue, so I bought a replacement. Now fitted, I ran the engine but the gauge again hardly moved. This time it didn't even go up to 1/4 like before. I've got a multimeter that can read temp, so i attached the sensor wire to the water outlet housing (same as where the factory temp sensor mounts). I ran to engine to almost 100c, but no movement on the gauge! Odd thing is the radiator fans didn't come on either? They worked fine last time I drove the car. Do they take their signal from the same temp sensor? Any suggestions on what might be going on?
Thanks, BB

[EllsoJo]

I remember reading somewhere that there are TWO engine temp sensors, one for the gauge, and another for the ECU for engine mixture management & control of cooling fan(s). A picture of a K series out of the car is attached:

Coolant temp & oil pressure sensor locations

I seem to remember that the colours of these changed at some time, so you have to get the right one for the age of your car. Also they can be damaged if twisted?? May be wrong there!

[mgf15]

Thanks for the reply. I bought this one as the replacement for the temp gauge sensor. Have I made a mistake?

https://rimmerbros.com/Item--i-MEK100061P

Thanks,

BB

[EllsoJo]

The only "Safe" answer I can give is: Sorry, not sure. What will be more helpful to you is the suggestion of searching this site by entering something like "Temperature Sensors" into the search box (Top Right of the opening page when you are on this Forum).

I did that and a lot of useful information and relevant threads appeared. You will have to choose which threads apply to your (Presumably Mk1) 1997 MGF.
Good luck!

[Rob Bell]

Thanks for the reply. I bought this one as the replacement for the temp gauge sensor. Have I made a mistake?

https://rimmerbros.com/Item--i-MEK100061P

I think so yes. I have to say that the Rimmer Bros diagram is extraordinarily unhelpful in this instance - although actually not their fault, as they have lifted the original RAVE parts diagram from Rover to build their website. As EllsoJo says, there are two coolant temperature sensors used on our cars, both mounted on the water outlet stub at the top of the cylinder head. One is for the temperature gauge, while the other is for the ECU to adjust ignition timing etc. I think you've replaced the latter rather than the former. The sensor you need, on the Rimmer's diagram, is part 25.

[mgf15]

Hi Rob,
Thanks for your reply. Yes the Rimmer Bros website and details are a bit sketchy to say the least. I'm not sure sensor #25 is the right one either. When I checked the description at the bottom of that page for sensor #25 it says its the "audible warning temp sensor". The one I bought has a description that says "switch has a black plug but it is a replacement for the brown plug as supplied by MG Rover and Land Rover". And it appears recent research indicates that the original brown sensor is the one for the engine ECU not the gauge? I asked Rimmer Bros to confirm but I'm still waiting for an answer. Very confusing for such a simple job! Surely someone has bought a gauge sensor recently?
BB

[mgtfnut]

Try looking at Dieter's site

http://www.mgfcar.de/epc/1524.htm

I replaced one of them years ago, and have forgotten which is which

[Rob Bell]

Try looking at Dieter's site

http://www.mgfcar.de/epc/1524.htm

I replaced one of them years ago, and have forgotten which is which

me too - but the wiring colours on Dieter's website should resolve the question, although which if the sensors to order from Rimmers is another question!