Temp gauge problem? 307 SW

Hi all:

the following happens with a 2002 307 SW (1600 cc): the temp gauge used to
run steady at 90 degrees (Celsius, approx 194 Fahrenheit) when the motor was
warm. All of a sudden the temperature indication has dropped to 75 (Celsius)
when warm. The temp instrument seems ok. The dealer cannot find anything
wrong with the car. But obviously something MUST BE wrong. Can it be a
faulty thermostat instructing more coolant flow through the system? Please
suggest things to look for. TIA,

Nikolas

ps. The drop in temp indication cannot be attributed to weather conditions,
which have remained steady over the period of this change. The coolant /oil
has not been replaced either.

 

They do have problems with the temperature sender unit, which supplies
the gauge. As it's under warranty, they should be able to sort it out
using the Diag 2000. It will probably mean a new sender unit (the
green one).

 

Sincere thanks for the tip. For my education: is the Diag 2000 their
diagnostic equipment? Where is the temp sender unit located? I was just a
bit confused by the statement "As it's under warranty, they should be able
to sort it out using the Diag 2000".

Thanks again,
Nikolas

PS. Unfortunately, the car is not under warranty... :-(

 

Ah, right, so you're not from the UK then!
The Diag 2000 is the diagnostic equipment.
The sender unit is on the thermostat housing.