My Temp guage in my EF Futura goes up and down constantly.

EG, been driving around for 30 minutes, im on the highway, look down at the temp guage, its sitting BEFORE the L (where it says NORMAL)

then about 8 seconds later i look again and its nearly above the A

then i watch it slowly go back down to below L again in the space of 10 seconds.

All this while maintaining a solid speed of 100k/ph

Any ideas?

Not sure if this is the same problem, but my EL would go from a good normal temperature right up into the red (red lights and all) and then after a while back down to normal. Turned out the sensor was dirty, cleaned it up with some carby cleaner and it worked a treat after that.

excuse my ignorance, but where exactly is the sensor?

In the thermostat housing, at the front of the motor, the housing is bolted onto the bbm.

ah yea, cool ill take that off and give her a clean, she's slowly leaking coolant there, so its a good excuse to change the housing gasket.