temp gauge reading hot when cold

[oatesy39]

Drove car 3 mile turned of rad fan was on came back after work she wouldn't start battery flat tried turning over fan came on again with ignition of turn ignition on it gos of temp gauge is reading red hot, called break down guy got it going but wouldn't rev at all turn of fan and temp gauge still the same, it's been been plugged in but no faults coming up ..can anyone help...2007 ddis 1.8

[Anton]

Sounds to me like there's a short in your temp sensor circuit. Your temp sensor is (unless I'm going mental) essentially just a thermistor - a resistor who's resistance goes up as temp comes down.

If the live wire and the ground wire in this circuit short together, your ECU will think the temp sensor is about to become molten metal.

The ECU will keep running the fan so that your engine block can cool off.

This will drain the battery.

The ECU will probably also run your engine leanish because it thinks your engine is red hot, and won't richen the mixture for cold starting. It may also be deliberately putting you in a limp mode to limit engine heat and prevent damage to the engine - probably why it wouldn't rev. Maybe. I'm not an ECU expert.

Get someone with a multimeter to check your temp sensor. It might be burned out and offering no resistance at all, or maybe the wires have rubbed on something and now they're shorting. A multimeter will let you know if either of these things are the fault without much fuss.

This is what I *think* is wrong with your vehicle (1.8 DDIS - Grand Vitara?). Hopefully that's it, because it's a relatively simple fix if I'm right. If not, then your ECU might be faulty, and that's a much more expensive fix if it is.

If it's not the thermistor, shower Rhinoman in many gifts, he's the resident ECU expert.

[oatesy39]

Thanks for the reply mate will get the garage to look into it on Monday will let you know how it goes

[oatesy39]

Sounds to me like there's a short in your temp sensor circuit. Your temp sensor is (unless I'm going mental) essentially just a thermistor - a resistor who's resistance goes up as temp comes down.

If the live wire and the ground wire in this circuit short together, your ECU will think the temp sensor is about to become molten metal.

The ECU will keep running the fan so that your engine block can cool off.

This will drain the battery.

The ECU will probably also run your engine leanish because it thinks your engine is red hot, and won't richen the mixture for cold starting. It may also be deliberately putting you in a limp mode to limit engine heat and prevent damage to the engine - probably why it wouldn't rev. Maybe. I'm not an ECU expert.

Get someone with a multimeter to check your temp sensor. It might be burned out and offering no resistance at all, or maybe the wires have rubbed on something and now they're shorting. A multimeter will let you know if either of these things are the fault without much fuss.

This is what I *think* is wrong with your vehicle (1.8 DDIS - Grand Vitara?). Hopefully that's it, because it's a relatively simple fix if I'm right. If not, then your ECU might be faulty, and that's a much more expensive fix if it is.

If it's not the thermistor, shower Rhinoman in many gifts, he's the resident ECU expert.

hi mate the garage is saying the ecu is as good as fucked they disconnected the temp sensor which worked and put the gauge back to cold but motet still won't rev up and the ecu keep going nuts when plugged in. Hopefully they can get the ecu repaired so it don't cost ad much..

[Anton]

Ah. If it's your ECU at fault, then my helpfulness will be at an end as I don't know much about them. I know theory, that's about all.

The reality is something else. I could plug a computer into an ECU and read error codes - that's about as useful as I could be to you.

Hope it's sorted soon!