Help! Ford fiesta 1991 with temperature sensor problem

[smokingjoe]

Hi chaps.. not sure if anyone can help with this problem but would be grateful for any advice.
I have aFord Fiesta van with a 1.1 petrol engine. About three months ago it developed a overheat reading problem with the guage going off the scale on start up from cold... I checked the coolant which was stone cold so drove the van home... After about 10 miles the guage dropped back to normal temperature (very odd) and stayed there for the next 10 miles. The next morning the same problem.. And again after 10 miles or so the guage dropped back to normal. No problems with starting, running or overheating.. Having talked to a local motor parts co they said it is pretty certain to be the sensor.. which I changed but the problem remained. I have changed the sensor again but still have the same problem. I have disconected the wire to the sensor to see if there is a short anywhere but the guage shows the disconnect and drops off to zero, when reconnected its back up to being off the scale. If anyone can help I really would appreciate. Thanks..

[DennisTheMenace]

Sounds like the sensor has a short , or the wire is earthing somewhere

[smokingjoe]

Hi, thought the same but when switching on the ignition (and leaving it) the reading stays at zero then when starting and running the engine for a few short mins the needle goes into orbit.. Sure it must be the sensor but have replaced it with 2 new ones and the same problem.. Thanks anyway.