I seem to have an issue with the Temp Gauge on my Paseo but not sure what is causing the issue. If its the Radiator or perhaps the Thermostat.
When the car starts up in the morning it takes a while for the Temp Gauge to make it to 1/4 position and as soon i as start driving it starts to fall.

So on a cold morning it seems the temp gauge is reading what the external temp is and if i turn the heater on it behaves the sameway.
On a Summers day when i stop at the lights the Temp rises to 1/2 but when i start moving with the traffic doing 60km/h + it falls back to 1/4 or even lesser
if its cooler outiside.I have never heard my Radiator fan come on when the Temp rises. In my 05 Corolla the needle on the gauge always sits on 1/2 when its
warm(running temp) and the fan kicks in if i sit idle for too long.Fan noise is always loud so i would never miss it if it came on in the Paseo.

The reason i have doubts about the radiator is when i flushed it sometime ago it didnt take the full 5 litres of coolant. I think it only took about 3 odd litres.
Maybe there is a blockage in the radiator and the water doesnt heat rapidly when i drive at 100km/hr but i'm not sure if its got anything to do with the temp
fluctuation and this is where i'm seeking advice. The heater/blower blows air according to the temp gauge.So when its at 1/2 its blowers warmer (In Heat Position) and when i'm on the Highway doing 100mk/h it falls (gauge) and the blower blows cold air even when its in Heat position.

Winter mornings are cruel this way especially when l leave for work at 4am.Might as well drive with my window down any freeze myself as the Heater is useless.

Any suggestions would be great guys , just not silly ones ..lol

Either:
*open thermostat
*faulty sensor
Both are easy and cheap to replace, so worthwhile looking into replacing both of them. Drain your coolant, see how much is in there. I don't think there would be a blockage, but weirder things have happened.
My radiator fan very rarely comes on, it's due to the fan-turn on point being set rather high.

Judging by the fact that he said when his heater is on, the air gets cooler as he drives, indicates that it is more likely an open thermostat than a faulty sensor.

thanks guys .
i will tackle the Thermostat first and update with results.

Hi guys ,

thanks for the suggestion regarding the Thermostat.
Changed it yesterday and $28 later problem fixed! Gauge is now behaving like its meant to be .


Accidentally did end up breaking a Housing bolt. Got too carried away tightening it but its cool as there are no leaks yet.