Problem on my daily car

[Scottcooper85]

Okay so we've got a 1.6 58 reg astra as our family car. About 3 week ago the fault light came on the dash but the car ran fine. I took it to the garage which is owned by a friend he found the fault to be the coolant temp sensor so it was changed and the code reset. About 10 miles use later the fan was permanently running and the car wouldn't fire at all from cold unless easy start was used and then it ran very lumpy until warm, which to me says the coolant sensor was telling the car it was red hot when it was cold. Anyway got another put in which cured it until I got to PVS Sunday and went to fire it and managed to get it out running pants until warm. Then today he's tried a genuine GM sensor but I'm just waiting for it to go again. Any ideas if it goes what else could be causing it as I don't want to start changing needless stuff?

Thanks in advance for any knowledge

[tomfromdelmonte]

Hi, my understanding is that the coolant sensor is a very simple part which shouldnt need replacing often. It is just a variable resistor (known as a thermistor) with a resistance that changes relative to temperature. I think the ecu probably injects a voltage onto one wire and measures current flow to provide a sensor reading. Either way i think its more likely that there is a problem with the ecu and/or the part of the ecu that deals with this sensor. If you have tried several sensors and the problem reoccurs then that should tell you something, btw this is the same engine that i have in my rally car. It might help to have an obd reader handy so you can read engine codes every time the fault appears, dont take someone elses word for it, check the code yourself and make sure it is the temp sensor. You can get a cheap chinese obd reader on ebay for less than a tenner.

[Scottcooper85]

Okay mate I'll look into them, since the first time it hasn't thrown up a light would it still show a fault code through a reader? I did wonder about the ecu as that and the fan are the only parts that really interact with that sensor. Hoping it's not going to get too expensive if it happens again lol