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Justtellme



Member Since: 23 Nov 2015
Location: Ottawa
Posts: 305

Canada 2003 Defender 110 Td5 SW Oslo Blue
Temperature gauge
I know this might be anal retentive and long but…..need some input on a 2003 110 Temp gauge.
I understand the gauge is controlled/ modulated by the ECU and operates like any analogue gauge up until about 1/2 scale. Once overheat condition is detected, it increases output to the red zone in a step function like response.

Until a few months ago, the needle always rested just to the left of center which is what I was used to.
At that point, I had a leaking radiator which I then sorted with a brand new Nissens along with a new aftermarket Motorad thermostat.
Refilled and followed normal procedure for ensuring no air in the system. Out of curiosity, tested the old thermostat in hot water and seemed to be fine.

The gauge then started reading at exactly center scale rather than just below center( approximately 1.5 needle widths higher than normal compared to the last 7 years I’ve owned the truck.)

Replaced thermostat with the original genuine one and tested the motorad which seemed to open only about half as far as the genuine one, so popped the genuine one back in and ordered a new genuine one from the UK.

Gauge then still read exactly center of scale. Plugged in the Nanocom and it never seemed to go above 94/95 and usually stayed in the 91/92 region when moving and up to 94/96 when stationary idling in traffic and fully warmed up.

Drove the truck 1500km home to Ottawa last week (from where I’m deployed in Halifax)with some gear in the back (approx 500-600 lbs worth?)
While running at high speed (120 km/h) in the mountains, the gauge decided to jump to 1.5 needle widths above center and stay there. The nanocom seemed to indicate the motor was running about 1-2 degrees higher fully warmed up, but there were also a number of excursions where it would jump around 5/6 degrees instantaneously. ( suspected the sender might be on its way out….)

After entering Ottawa at the end of an 8 hour leg where it was 32+C, it jumped to around 98/99 according to the nanocom at idle in traffic.

After getting home and waiting for cool down, I swapped the temp sender in the outlet elbow for the diesel temp sensor to see if that would make any difference. According to nanocom, the temp was now rock solid at 91.1 when fully warmed up around town in most conditions with no excursions.

Temp gauge still reads 1.5 needle widths above center. I hate change…….so want it back where it always has been…1.5 needle widths left of center….

Is the temp gauge modulated by any other sensors or inputs? Is there anything else that might be causing the gauge to read higher at normal operating temp even though the nanocom shows all is well?

Relay corrosion somewhere? Ground points on gauge/ bulkhead/ chassis? Seems strange the new permanent change to the gauge when fully warmed up seemed to be related to the truck working hard or following a radiator leak…..no oil in the loom, new Turner head and injector loom about 2 years ago.

Any ideas on where to start? ( I’ve already order a new Bosch sender for the coolant along with the genuine thermostat)

Patrick
Post #955896 19th Jun 2022 1:00am
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miker



Member Since: 13 Sep 2015
Location: Surrey
Posts: 1758

United Kingdom 1999 Defender 110 Td5 CSW Rioja Red
Earthing issues can definitely affect it. At one point my temp guage moved depending on how far I was pressing the throttle pedal down...

I didn't do one specific thing to fix it though, I sorted a whole load of wiring bits at the same time.
Post #955921 19th Jun 2022 12:34pm
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Justtellme



Member Since: 23 Nov 2015
Location: Ottawa
Posts: 305

Canada 2003 Defender 110 Td5 SW Oslo Blue
Thanks,
I’ll pull the gauge cluster first and work my way back to the underseat compartment….
Patrick
Post #955980 20th Jun 2022 12:25am
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A.Rubio



Member Since: 04 Mar 2017
Location: Rocafort -Valencia
Posts: 27

Spain 
Regarding the operation of the temperature gauge, as you said, it is managed by the ECU but when it goes above a certain degree, the ECU controls it and the gauge does not move, it continues in the same range without reflecting that increase in temperature. In order for this instrument to move freely according to the increase or decrease in temperature, some parameters of the ECU must be modified, as I understand it.
Post #956036 20th Jun 2022 7:19pm
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