Warning Signal in Temperature Gauge (TD5)

[Dariusz]

As everyone knows, in the TD5 Defender Dashboard the temperature gauge receive its signal from the ECU. This signal tell the gauge what is the needle position, but it also indicates if the shock sensor is activated (the needle will stay full), or does "jumps" to full to indicate that the temperature is hot and outside the normal range.

I like to install a LED that lights up when this happens.

I need to know several things of this signal:

1. What is the range of work? What is the value when going to Full?
2. The signal is a voltage? Positive? Negative?

Thanks in advance for your help,

Dariusz W.

[Graeme]

I do not know if the Defender TD5 ecm produces the same temperature signal as the D2 TD5 ecm but the D2's is 12V pwm with the duty cycle used to indicate the temperature. 76.8% duty cycle for 118 deg C and 78.8% duty cycle for 121 deg C, values documented in the D2 WSM. 127 deg C was the temperature at which the gauge needle dropped to the bottom of the scale indicating gross overheating. At low temperatures the observed duty cycle is not linear to the scale derived from the bove temperatures but inconsequential if monitoring high temperatures as I was.

I flashed the D2's gearbox overheating dash indicator progressively faster and beeped an alarm for longer as the temperature raised from 107 deg to 118 deg, at which temperature my alarm sounded continuously and the light hard on. When idling along in top gear in hot weather and the a/c on the alarm would start to beep prompting me to change to the next lower gear.

[Dariusz]

Thanks Graeme,

I'm not sure to about if the D2 and Defender ECM use the same for the temp.

You say:

... 127 deg C was the temperature at which the gauge needle dropped to the bottom of the scale indicating gross overheating.

Is to bottom or is a mistake and is to the Top of the scale? Bacuse in that situation the Defender go to Top

[Graeme]

The D2's needle would eventually get into the very short top red section but then at a slightly higher temperature would drop to the bottom and an amber warning light within the gauge would be illuminated. This double action was meant to better alert the driver to the excessive temperature although by that time the head was usually destroyed.

[BilboBoggles]

Personally i would make it an independent sensor. One of those 12v ebay thermostats driving the led. and a sensor bolted to the cylinder head. I believe the td5 has a coolant sensor which if you lose the coolant quickly wont react in time to save the engine. A cht will. I run a tm2 in mine and its very reassuring.