Engine temperature gauge going full scale

Hi all,
I'm new to this forum and having owned my C3 1.4 SX for many trouble free years, it has developed an annoying fault when standing stationary in traffic for a long time. The engine temperature gauge goes from 3 bars to full scale for about 20 seconds then it goes back down again. Therese no excessive engine heat and the fan doesn't kick in. I'm convinced its not over heating because the gauge doesn't gradually come down to normal its just drops straight back down. This only happens when in stationary traffic. I read somewhere that its one of the temperature sensors at fault but I don't know which one as the petrol engine has two, upper and lower.

Has anyone else had this problem and how was it rectified ?

Thanks, C3mally.

Hello C3mally,

For the petrol C3:
The sensor thats fitted to the head (upper) is the one that sends the signal to the temprature gauge and the one fitted into the coolant oultet housing (lower) send the signal to the ECU/BSI.

The Diesel only has one sensor (the lower)

Hope this helps

Thanks but does anyone know which one I should change?. One costs about £15 the other £30 so it would be nice to get it right first time to avoid unwanted costs.

Thanks, C3mally.

Sorry C3mally,

Its the head (upper) is the one that sends the signal to the temperature gauge on the dashboard display. This would be the one to change IF its faulty. As there may be a problem with the wiring to the sensor, maybe a break or short in the cable or a faulty display on the dashboard and ..

The temperature sensor wiring passes via the coolant level sensor (that is, coolant level and coolant temperature are part of the same circuit), also ECU then BSI.

My first choice for checking would be coolant level sensor (and coolant level),

then upper temperature sensor wiring (plugs, sockets wires), then upper temperature sensor itself, then BSI and then Display Module and ECU lastly.

There is a forum post in this link detailing which antifreeze/coolant to use in your Citroen C3 if it needs topping up or changing.