radiator fan switches on when turn car off

[genoff2000]

Hi All

I have a 03 s40 19td, I have read various posts about faulty temp gauges, which my car has, the temp goes from really hot even when i turn it on first thing in the morning, the next minute
cold and then hot again.

the question i have is when i am out driving weather it be a 5 minute drive or a 55 minute drive
when i turn of the car the radiator fan stays on for about 5 to 10 minutes

the fan only comes on when i turn car off, if i start the car the fan goes off.

the fan will operate if i am sitting in traffic

is this normal or do i have a faulty radiator temp switch

any info would be great

cheers

g

[stevo48]

Faulty temperature sensor, do a search for it, theres plenty posts about it on this forum

[mfaw23]

Had experienced this when my head gasket was failing.....coolant lost into engine causing engine too hot. Yours could be different if if u do not experience coolant lost

[Neo123]

Originally Posted by mfaw23

Had experienced this when my head gasket was failing.....coolant lost into engine causing engine too hot. Yours could be different if if u do not experience coolant lost

what year was your car?

i have slight coolant loss, but my car works fine. Its use to happen in my car also the fan running after i switched the car off.

Also it was taking ages for the car to warm up so i've change the thermostat.

[Nickmac]

Had this exact same problem, on mine the wiring was breaking down where it enters the temp sensor plug on the cylinder head. A bit of soldering and it was sorted out.
By the way, always check the plug/wiring before replacing what can be quite expensive sensors, sometimes you can save some money by not buying something that you did not need to replace! (think that made sense! well it did to me anyway!)

[mfaw23]

neo123
mine was not slight coolant lost but rather a lot. when the gasket became totally fail, its like the coolant level suddenly recede as if the engine drank it when idling.

mine was yr 99 and 170K miles and the engine was changed (used one i guess) by previous owner. Its good to keep an eye on that green liquid level.

[rthackery]

Had exactly same symptoms and the cause was exactly the same as that described by Nickmac. Fully endorse his suggestions

[genoff2000]

Hi Guys

checked the wires on the plug and it was broke

made up new connections to the temp sensor sender unit and connected them to the wires a
all seems well at the minute.

I did not think that the temp sensor sender unit was linked the to radiator fan, cause there is a temp sensor on the radiator

but thanks for the help and advice

G

[Nickmac]

The system is connected, the ecu uses info from both the rad sensor and the head sensor to work out what the temp is, if either of them is high or appears to be high (in this case) the ecu switches in the fan(s) as a precaution.
Computers have no way of knowing that a signal is faulty, they just act on the information received, in this case incorrectly.
Glad you got the problem fixed easily, it is a very common problem as the loom doesn't have enough wiring length for the sharp bend it has to turn. Volvo are well aware of this too but I don't think they ever had a recall for it. Much the same as the old loom under the radiator failures!

[wa666ou]

I have T4 and when I had problems with my fuel pump, actually the filter in the tank, fan started exactly the same way.
Car was cold, but when I switched it off, fan started to work...
I guess faulty fuel pump made ECU go crazy.