temp guage jumping about and eratic idling

[Andy1.6hlx]

when driving about the temp needle will be sitting at half then suddenly jump to 2/3 then a minute or so later drop staight back down to half, pulled into fill up and needle was at half, turned her back on and was up at 2/3 so turned her off again and back on, and then it jumped between half and 2/3 a couple of times before settling down

i've also been getting some eratic idling and sometimes it stalls, but only rarely...

i thought the fan wasn't working but it came on today so it obviously does.

if anyone knows what this could be i'd really appreciate some help, thanks guys

 

[andyb76]

could thermostat my gauge was jumping about one minute really cold next minute hot so i change it and its been fine every since

 

[Andy1.6hlx]

it never dipped below half way though :S

and also would the thermostat affect the idling?

i was thinking maybe it could be the temp sensor but i wanted people's thoughts before i buy any parts