Vauxhall Astra running hot and cold

[scottiey]

Vauxhall Astra 1.6 1996 (P Reg)

MY car has a problem with deciding how hot it wants to be, the heating line varies when driving it. When stationary the car temp rises to between 90 and 100 and when driving its below 90 (just above the blue (cold) line)

Also on the dash a yellow light flicks on and off for varied periods of time. (a sketch of an Engine with a spark/lighening flash in the middle. Any ideas?

Cheers Scottiey

p.s Coolant is topped up , fan works oil is topped up

[2 litre]

Vauxhall Astra 1.6 1996 (P Reg)

MY car has a problem with deciding how hot it wants to be, the heating line varies when driving it. When stationary the car temp rises to between 90 and 100 and when driving its below 90 (just above the blue (cold) line)

Also on the dash a yellow light flicks on and off for varied periods of time. (a sketch of an Engine with a spark/lighening flash in the middle. Any ideas?

Cheers Scottiey

p.s Coolant is topped up , fan works oil is topped up
the flickering light is the engine management light you need to get the ecu read for codes temprature sounds normal ;)