Interior thermostat?

[Scribe]

Heater comes up to temperature but then doesn't maintain it.  Also, the air conditioning doesn't seem to do much even after being re-gassed.  Could this be something to do with the interior thermostat?  Engine temperature is fine.

[steve2006]

Possibly, there is a thermistor temperature sensor mounted behind a little colour coded intake grille on the left side of the driver’s footwell, look at the parking brake then look slightly left on the side carpet area.

Cabin air is sucked past the sensor and that provides the required data to maintain the set cabin temperature.

Problems develop when carpet fluff clogs up the vent and sensor.

A blast with compressed air through the intake grille normally clears it.

[Howplum]

I had exactly that problem on a Mercedes-Benz SL and cleaning the sensor solved the issue.

[Scribe]

Thanks Steve.  I have an MOT coming up so will get the garage to do a few other jobs (including new bonnet struts recently bought).