93 Corolla 4A-FE running very cold

[NeilMH 11]

I have 3 E10 Corollas (amazing but true!) all with 4A-FE 1.6 engines. I know the weather is cold but one of them is now showing very low engine temperature when on longer runs - i.e. between the bottom line and the first line on the gauge. The others both show higher readings (between 1/3 and just below centre) in exactly the same conditions. Is that anything to be concerned about or is it just likely to be a deteriorating sensor through age? I realise that running cold is a lot better than being too hot. I just want to make sure I'm not missing something that could be more serious.

[frizzbee30 30]

Usually this is down to the thermostat failing open, typified by taking longer to warm up from cold, obviously on a long run the airflow will exceed any fan capacity. 

It can be down to a sensor issue too, but generally mechanical stats fail first 🙂

[NeilMH 11]

Thank you frizzbee30 - I'll have to keep an eye on that and will probably get it changed as a precaution.