Technical 2016 Ducato based motorhome external temperature sensor replacement

[Hymer544PL]

This thread is to record how I fitted a replacement temperature sensor on our Hymer B544 PL motorhome that is based on a Fiat Ducato X290.
Symptoms: Temperaure shown on the display was extremely high and erratic, often over 80°C, finally settled at ---°C so it looked like the sensor had failed.
A great deal of searching the internet showed that many people had the same problem, and it was caused by failure of the external temperature sensor. Normally this sensor is fitted to the bottom of the mirror on the driver-side, that is OK on a standard van or van conversion motorhome. Many motorhomes (A class) have custom mirrors and bodywork, so the external temperature sensor is placed somewhere else by the builders of the motorhome, and there is the problem, WHERE is the sensor? Eventually I decided that fitting a new sensor was the only sensible option.

Thanks to HughJampton on this forum for the X290 Converter's Manual that enabled me to solve this problem.

Steps in solving the problem

• Carefully studied the Fiat Ducato Converter’s Manual that shows the electrical connections. Established that connector Y001LA was what I needed.
• Found the appropriate connector on our Hymer and established the correct wires that go to the external temperature sensor.
• Cut the wires and attached a variable resistor set to 10k ohms, this is to confirm that these are the correct wires. 10k resistance is 25°C on the display.
• Purchased a replacement thermistor temperature sensor.
• Constructed a new external temperature sensor housing and found a suitable location on the Hymer.
• Attached the new sensor and installed wires to connect it.
• Tested and confirmed it works.

Difficulties:

1. Finding the Y001LA connector on the motorhome, it is behind a lot of plastic fascia and there are NO labels or identification marks on any of the connectors. I had to remove each connector and count the pins carefully.
2. On the socket side of the connector the wires are coded using Fiat wire colours but on the plug side the wires use Hymer wire colours so they are totally different. I did not recognise that for some time.
3. Some of the pins in the connectors are not used, so there is no wire, but you still need to count those pin positions, otherwise you cut the wrong wires, that's what I did and then spent a long time wondering why I saw no change on the temperature display. To ensure that I finally had the correct wires I attached a variable resistor in place of the sensor so that I could simulate the temperature change.
4. Finding a suitable place to locate the new sensor so that it would not be affected by heat from the engine and also finding a place where the new wires could be routed conveniently.

I purchased a sensor via a well-know auction site on the internet, it arrived quickly.
The sensor was attached to a new support bracket as shown below . . .

then attached to one of the rear support brackets of the vehicle using cable ties, as shown below . . .
The sensor should remain dry there.

the wire from the new sensor is routed through and existing hole into the battery box of the vehicle, then to the appropriate connector.

In total this project has probably taken 3 days, if I had known what I now know I would have finished it in 1/2 a day, but that's how things go.
Hope this helps other people with the same problem.
Final result, temperature showing . . .

 

[the green vanper]

Congratulations, good job! And good idea to use the starting battery compartment to run the wires outside

Pity they made the display screen smaller again

 

[Fiatadriasonic]

This thread is to record how I fitted a replacement temperature sensor on our Hymer B544 PL motorhome that is based on a Fiat Ducato X290.
Symptoms: Temperaure shown on the display was extremely high and erratic, often over 80°C, finally settled at ---°C so it looked like the sensor had failed.
A great deal of searching the internet showed that many people had the same problem, and it was caused by failure of the external temperature sensor. Normally this sensor is fitted to the bottom of the mirror on the driver-side, that is OK on a standard van or van conversion motorhome. Many motorhomes (A class) have custom mirrors and bodywork, so the external temperature sensor is placed somewhere else by the builders of the motorhome, and there is the problem, WHERE is the sensor? Eventually I decided that fitting a new sensor was the only sensible option.

Thanks to HughJampton on this forum for the X290 Converter's Manual that enabled me to solve this problem.

Steps in solving the problem

• Carefully studied the Fiat Ducato Converter’s Manual that shows the electrical connections. Established that connector Y001LA was what I needed.
• Found the appropriate connector on our Hymer and established the correct wires that go to the external temperature sensor.
• Cut the wires and attached a variable resistor set to 10k ohms, this is to confirm that these are the correct wires. 10k resistance is 25°C on the display.
• Purchased a replacement thermistor temperature sensor.
• Constructed a new external temperature sensor housing and found a suitable location on the Hymer.
• Attached the new sensor and installed wires to connect it.
• Tested and confirmed it works.

Difficulties:

1. Finding the Y001LA connector on the motorhome, it is behind a lot of plastic fascia and there are NO labels or identification marks on any of the connectors. I had to remove each connector and count the pins carefully.
2. On the socket side of the connector the wires are coded using Fiat wire colours but on the plug side the wires use Hymer wire colours so they are totally different. I did not recognise that for some time.
3. Some of the pins in the connectors are not used, so there is no wire, but you still need to count those pin positions, otherwise you cut the wrong wires, that's what I did and then spent a long time wondering why I saw no change on the temperature display. To ensure that I finally had the correct wires I attached a variable resistor in place of the sensor so that I could simulate the temperature change.
4. Finding a suitable place to locate the new sensor so that it would not be affected by heat from the engine and also finding a place where the new wires could be routed conveniently.

I purchased a sensor via a well-know auction site on the internet, it arrived quickly.
The sensor was attached to a new support bracket as shown below . . .
View attachment 441252
then attached to one of the rear support brackets of the vehicle using cable ties, as shown below . . .
The sensor should remain dry there.
View attachment 441253
the wire from the new sensor is routed through and existing hole into the battery box of the vehicle, then to the appropriate connector.

In total this project has probably taken 3 days, if I had known what I now know I would have finished it in 1/2 a day, but that's how things go.
Hope this helps other people with the same problem.
Final result, temperature showing . . .
View attachment 441254

Hi
I am new in this forum, From DK.
I am having, as Many, the exact same problem with my motorhome Fiat Adria Sonic. Found the wire for the temp sensor, but maybe you could tell me where to buy the new sensor? Dont know the website you are referring to
Hope you can help

 

[the green vanper]

The original FIAT sensor can be bought on ebay, you could also check the dealership. And other companies that sell spare parts for the automotive market. On the photo posted by @Hymer544PL I can see it looks like the original FIAT sensor. The part number should be 1375410080. There are also aftermarket parts available. Check it the connector is correct, there could have been different ones fitted. But if so, replacing one is an easy job.

 

[Fiatadriasonic]

The original FIAT sensor can be bought on ebay, you could also check the dealership. And other companies that sell spare parts for the automotive market. On the photo posted by @Hymer544PL I can see it looks like the original FIAT sensor. The part number should be 1375410080. There are also aftermarket parts available. Check it the connector is correct, there could have been different ones fitted. But if so, replacing one is an easy job.

Okay, thanks.
My dealer says the sensor is part of the mirror which is not correct on my camper. The sensor is mounted in the front fender and it looks like the one in the picture from @Hymer544PL which I haven't been able to find on ebay. But I'll try the number here.

 

[the green vanper]

Originally it is in the driver side mirror, but as you have different mirrors, they decided to put it elsewhere, in your case in the fender. If you look the part number I gave for over the internet you'll see that the sensor has the same shape as the part that @Hymer544PL marked as 'actual sensor' on the first picture he posted. You should be able to cut the heat shrink, pull out the wires through the sleeve and then replace the sensor with cables and add a new heat shrink on top.

Another solution is to cu the wires below the sensor and solder the new sensor in place to avoid playing with the cables. Before you start, check that the problem is not in the plug or the cables!