Technical [244] Weird behavior of temperature gauge - where to look?

[kotperski]

Hi all.
I'm owner of 2003 Ducato 2.8 JTD. Today I noticed really weird behavior of my temperature gauge. Please let me describe in details:

• During normal motorway driving the needle suddenly went from half of the scale (normal position for warm engine, just below half mark) to the red area. Not exactly to red, just touching its lower part.
• I've made a quick stop to cool the engine. After switching the engine, needle drops to bottom, as usual. After 15 minutes of waiting, I've turn the engine on, needle immediately went to the previous position, touching red mark. Apparently cooling didn't work
• Of course I've checked everything possible - coolant level was proper, temperature of reservoir tank was proper (warm, but far from being hot, easily to touch), no excessive pressure in reservoir tank, cooler warm, but not hot. Hoses in normal condition, excessive pressure. No leaks at all. Didn't manage to reach thermostat though. Engine didn't seem to be unusual hot by touch and/or smell.
• Fans did not start at all.
• No loss of power, no limp mode etc.

Making it short - everything seems to be perfectly OK, except gauge displaying worrying values. So I've connected OBD2 scanner (ELM327), installed few apps on my phone to get some readings. Two apps worked, both gave me temperature reading of 215°C - obviously completely awkward value. Well, intake temp reading was 215°C too. Interesting... No error codes found.

I know I should use Fiat EcuScan for gathering more realistic data, but the issue appeared while being about 5000 km from home, so no way to do it until I return

Please share some thoughts - gauge died, poor instrument panel soldering, temperature sensor died, thermostat died, faulty wiring or what?

Thank you in advance!

 

[Communicator]

Hi and welcome to the forum.

I do not like thanks in advance, as that is not how forums work. A post reporting the resolution is preferred.

OK then a shared thought, faulty sensor, or wiring, including the coonecor at the sensor.

The x244 2.8jts has two temperature sensors., a basic sensor for the ECU, which controls the fans, and another which operates the temperature gauge. This second sensor also contains a thermostatis switch for the warning light. It is this latter sensor that may be faulty.

Both sensors are mounted on the thermostat housing near the air filter and are difficult to see, without removing either the air filter housing, or at least one of the intercooler hoses.

The sensor that is the probable cause of your problem is the larger of the two sensors, and is designated K035 on wiring diagrams, which may not show the common earth connection via the metal body. It an M16 x 1.5mm thread, and is 22mm A/F (spanner size).

When I had my temperature gauge immediately indicating normal temperature with a cold engine, I prepared to change the sensor. Change was not neccessary, as cleaning the connections at the sensor cured my problem.

Below is a photo of the sensors which was posted by @Urco on a similar thread. The gauge sensor is the larger one , closer to the camera.

 

[kotperski]

Thank you for detailed reply. Your suggestion is 100% perfect - the problem is solved and you've earned my deep respect, sir!

I've removed both sensors, cleaned them thorougfully (sockets too), checked wiring and ensured all cables are attached firmly, eye-checked all wires and fired the engine up. Gauge at zero, after short driving engine got warmed up, gauge displayed just below half mark - so exactly as it should do.

Thank you again and have a nice day!