Technical Temperature Gauge issues

[GeX]

Right i have checked my versions of ePER (i have both the old models and new models)

Both use part number 46477022. This the expensive (~£30) temp sender for the ECU i think.

Then the other parts are:
On the Sei : 7588920. This is called a switch.
On the Cinq: 7588802. This called a sender unit.

They both go in the same place and cost the same. With part numbers that similar for very similar devices it would be very easy for someone employed by FIAT to pick up/order the wrong bit.

 

[arc]

yeah, thats why they're coloured coded. Red for variable, and white for not. I seem to have the correct bit.

 

[T14086]

Mmmm another avenue closed!

Theres a table here (halfway down the page) for 'approximate' resistances of temp sender at any given temperature,might be of some help?

http://www.mgcars.org.uk/electrical/body_temp.html#Table

 

[paul_treg]

Hi,
The resistance of my red top sender is 4.95k ohms at about 10DegC and about 150 ohms at about 75DegC. Checked the resistance back through the gauge and its 253 ohms between green wire and engine(ignition off).

Hope this helps
Paul T

 

[arc]

im foncused now. just checked my car, it has a black capped one in.

makes NO sense, will check properly tomorrow

 

[HP]

hmmmm. always thought the red top was for a switch...

 

[dastardly Dick]

Dont know if this will be of any help but my wifes 900cc cinq did this last year, it turned out to be the thermostat stuck open, small engine big rad the temperature never got above the minimum 50 degrees required to register on the gauge. a thermostat sorted it.

 

[fiat500]

The senders for the gauge on my cinqs are white topped

 

[arc]

ok, i think its the wrong part.

the engine is cold, and its givng no reading at all. Next time i use the car, i'l probe it then once warm - but i suspect it is the wrong part now.

probed the wire back to the dash - connected up to the gauge, it read 96ohm between it and ground

 

[paul_treg]

Hi,
Mines the same as the red top(works with gauge) one in the photo's you attached.......you will have to get the switch above 110c to test it as its an overheat warning light switch.....if that is the black one...?

Thanks
Paul T

 

[arc]

im going to give taking the engine to 110c a miss i think.

just going to get a new part from fiat, and test it in a kettle

 

[arc]

just probed it at operating temp, no reading. Its the wrong part. arse

 

[arseofbox]

Woo! getting somewhere!!

 

[Jefflun]

Hi,
Most sender units in modern vehicles operate at between approx. 100 and 300 Ohms resistance with 100 being equal to around 120-130 degress C and 300 being approx. 50 degrees C.
Remove the cable from the sender unit and try putting a 150 Ohm 1/2watt resistor (you should be able to buy this for a few cents at any electronics store like Jaycar etc) between the end of the cable and the frame or body of the car. The gauge should read somewhere around 1/3 or 1/2 scale or approx. 70 - 90 degress C. If this is the case it is fairly safe to assume you have a sender problem. You could also check the voltage at the end of the cable to the sender unit. It should be somewhere between 3 and 5 VDC.
Hope this helps.
Jeff

 

[randomizered]

2005

 

[arc]

it was an incorrect part from FIAT in the end. They gave me the 'switch' sender from a low model punto or a Sei.

All sorted now, but Jeffs post should still be useful for anyone attempting to diagnose similar problems