Temperature Gauge

Hi, I was wondering if anybody could offer me a little advice please as it seems that the indicator/needle on my temperature gauge on my TD5 is not really moving. When I put the key in and turn the engine on it moves slightly to the blue area, but then doesn't move even if the engine is hot.

I have filled the expansion tank and when I press the top hose it pumps the water in the expansion tank. So i presume there is water in the system?

Of course it would happen when somebody comes round to look at it to buy it... :-(

But now I am worried and have to take it to the garage... But being a women I would just like a little knowledge before i go to garage?

Please help, Thanks in advance, Teresa

gillybmw said:

But now I am worried and have to take it to the garage... But being a women I would just like a little knowledge before i go to garage?

Please help, Thanks in advance, Teresa

Click to expand...

Hi

I'm assuming your coolant level is ok. Also make sure your heater will blow warm, and that the radiator top hose is hot, after a run.

The temperature gauge on the Td5 is driven by the engine management ECU. This takes a signal from a sender unit mounted on the engine, whose electrical resistance changes with temperature.

The ECU works out the coolant temperature from the resistance, and drives the gauge on the instrument cluster. But it doesn't just move the needle in accordance with temperature. If the temperature is within a pre-chosen "safe" range, then it drives the needle to the middle. Thats why a Td5 doesn't seem to get warm when climb a steep hill, or cool down when descending on a cold day.

If the gauge does move a bit then it does sound as though the wire from the ECU to the instrument pack is OK. So most likely suspect is a fault in the sender circuit, perhaps faulty sender, or a wiring problem. It could be something as simple as the wire come off.

The ECU does need to know the coolant temperature, for its fuelling calculations. But in the complete absense of a signal, if the engine has been running for a certain time, then it assumes it must have warmed up anyway, and uses a default value for the fuelling calcs. I can't remember if it drove the gauge up or not, but I doubt it otherwise there's little to alert the driver of the fault.

Hope this helps, Bill

Take the wire off the coolant sender and ground it to the engine. Turn on the ignition.
The gauge should fly up to the hot end. If it does then your sender is kaput if it dont then you have a wiring problem.