Hi all,

I've recently aquired a cheap 1997 4.6 V8 that I've got an MOT on and seems to drive nicely. I've fixed a few issues like high idle, used MAF, new lambdas and bushes but one has me stumped.

The temperature needle on the dash doesn't move, if I short the connector out at the sender the red overtemperature light comes on but the needle is still on cold. Does anyone know if the light and needle movement are independent or if it should move to H when the light is on am I looking at getting some new clocks? I've connected the Nanocom and the engine ECU is seeing 90 degrees when the attached photo was taken.

Thanks, Matt.

As the sender doesn't drive the gauge directly but the signal from it is converted to a serial data signal to drive the gauge, it won't move the gauge when you short it. My theory is that the BeCM sees a dead short as a fault so doesn't try to move the gauge but brings on the light as a warning. It might give you a reading if you put a resistor across it but I've no idea what sort of value you would need. Early cars had a sender with just a single wire while later ones have the two wire green sender which I assume you have which is, unfortunately no longer available new so one from a breaker is you only option.

Gilbertd wrote:

As the sender doesn't drive the gauge directly but the signal from it is converted to a serial data signal to drive the gauge, it won't move the gauge when you short it. My theory is that the BeCM sees a dead short as a fault so doesn't try to move the gauge but brings on the light as a warning. It might give you a reading if you put a resistor across it but I've no idea what sort of value you would need. Early cars had a sender with just a single wire while later ones have the two wire green sender which I assume you have which is, unfortunately no longer available new so one from a breaker is you only option.

Thanks for the reply. I have fixed it by installing the green sensor I got into the pipe that feeds the top hose. The other sensor on the right I had already replaced. I had to swap the wiring over as the gauge cable had been put on the right hand sensor by the previous owner/garage. The sensor I took out of the left hand fitting was black so appeared on first glance to be the same as the right hand one but it wasn't and had a smaller thread so the green one clearly fitted there. I've attached a screenshot I stole from eBay to show what I'm trying to describe. Green on left, black on right. The incorrect black sensor is marked ES120-1 which appears to be "GENUINE ROVER COOLANT SENSOR Fits T SERIES 2.0 TURBO ENGINES."

That is absolutely correct. The green sensor that drives the dash gauge goes into the threaded hole in the top hose outlet, while the black one that feeds the ECU goes to the right in the coolant passage to the cylinder head. They have a different thread so you can't, or at least shouldn't be able, to get them in the wrong place. Plugs on the loom are also colour coded with the green plug going on the green sensor and the other one (which is brown on my car) going to the other one.