I've had a second occurrence of my Puma overheating sitting idle in traffic on warm days, thought I'd do a wee write-up of my 'fix/diagnosis'.
From reading bits and pieces here, I found that the temperature sensor is temperature-controlled resistor, essentially a heat-activated valve.
This is it here, right side of the engine, under the coil pack:
With the ignition at position 2 (not turned over) I tested the voltage coming from the fan power connector, ~14V, which is about right.
This is the sensor with the plug removed, I've put some little connectors on it to make it easier to keep my multimeter in contact with the sensor terminals
And with the multimeter plugged in
Removing the plug with a 19mm ratcheting spanner (hard to get at!), and sticking it in some cold water (12 deg.) it reads a resistance about 35K ohms.
Video of it going from cold to hot.
http://www.flickr.com/photos/43278150@N00/9386226360/" onclick="window.open(this.href);return false;
Back in the car, after running the engine hot (4 minutes @ 3000rpm), reading low resistance (<5k ohms).
In my case the sensor is working as it should, I just oscillated from hot to cold and back again 5 times, which combined with unplugging, cleaning contacts and plugging it all back together did the trick.
From reading bits and pieces here, I found that the temperature sensor is temperature-controlled resistor, essentially a heat-activated valve.
This is it here, right side of the engine, under the coil pack:
With the ignition at position 2 (not turned over) I tested the voltage coming from the fan power connector, ~14V, which is about right.
This is the sensor with the plug removed, I've put some little connectors on it to make it easier to keep my multimeter in contact with the sensor terminals
And with the multimeter plugged in
Removing the plug with a 19mm ratcheting spanner (hard to get at!), and sticking it in some cold water (12 deg.) it reads a resistance about 35K ohms.
Video of it going from cold to hot.
http://www.flickr.com/photos/43278150@N00/9386226360/" onclick="window.open(this.href);return false;
Back in the car, after running the engine hot (4 minutes @ 3000rpm), reading low resistance (<5k ohms).
In my case the sensor is working as it should, I just oscillated from hot to cold and back again 5 times, which combined with unplugging, cleaning contacts and plugging it all back together did the trick.
but just so you know, the temp sensos goes both to the dashm and the an, so if it's working on the dash its ok 
