1998 v70 engine cooling fan runs as soon as the car starts

lab133 · Post by **lab133** » 15 Dec 2010, 05:55

my v70 just turned 150k and for some reason the cooling fan has been running as soon as the car starts. so i went to the dealer and they told me it was probably the relay. so for 78.00 i went ahead and installed it. well it solved the problem at start uu , but when i shut down after my morning commute of about 20 minutes. the fan continues to run for approximately 2 minutes , never done that before,i wonder if the new relay has a different timer, and if it is now going to be this way always? and the car does have a/c with the auto mode

Post by **jblackburn** » 15 Dec 2010, 07:12

A bad coolant temperature sensor will cause this.

Have you noticed the dash temperature needle staying very low (under the normal 3:00 position) when moving?

Post by **mikealder** » 15 Dec 2010, 10:51

My year 2000 did exactly this when the thermostat jammed open although it also illuminated the check engine light on the dash, a new stat soon cured the issue - Mike

hammertime · Post by **hammertime** » 15 Dec 2010, 12:10

My 98 V70 did the same quite recently. Fan on before and after, CEL on, Temp gage only going to about 4 o'clock. Replaced thermostat and reset trouble codes and all is well. I could be wrong but I believe that when the car senses abnormal coolant temps, high or low, it trips into a safe mode where the fan runs all the time.

lab133 · Post by **lab133** » 15 Dec 2010, 19:59

ok the new relay did not work as first thought. the fan comes on as soon as the key is turned on. also noticed the temp gauge moving a little erratic. going to the normal operating temp position in about 2 minutes. popped the hood and felt engine .. cold as ice! so its back to the dealer for a sensor and thermostat..thanks for all the advice and will hopefully have some good results

lab133 · Post by **lab133** » 20 Dec 2010, 05:02

all is good, relaced the thermostat and sensor. runs like new

thehats00 · Post by **thehats00** » 26 Mar 2011, 00:14

Here's an FYI to everyone who has had this problem. I have read countless posts and followed much useful advice. I changed the temp sensor, the fan control relay, the maf sensor and the fan ran continuously. I finally found that none of these parts had been bad. When changing the temp sensor, I failed to notice the tremendous amount of corrosion inside the positive terminal of the sensor connector. Cleaned this, put dielectric grease on it and it sured the hard starting, the fan running and the lack of boost from the turbo. $250 in un-needed parts and several hour in wasted labor all because of corrosion in a connector. Always check the simple things first! Apparently a bad signal from the temp sensor causes multiple problems such as hard starting, fan override that forces the fan to stay on in 'safety mode' and it also tells the ecm to kill the turbo boost. Hope this helps.

Post by **Pauloil** » 26 Mar 2011, 09:00

another fact: you have to unplug a battery cable when you work on the sensor or other electric parts like O2 sensors. this resets the adaptives. a quick way to reset the adaptives is to press the batt cables together for 10sec.

michc927 · Post by **michc927** » 20 Mar 2014, 18:51

Where is the Positive Terminal of the temp sensor?

Thanks, Michelle

Post by **misha** » 20 Mar 2014, 20:44

michc927 wrote:Where is the Positive Terminal of the temp sensor?

Thanks, Michelle

If you're talking about ECT sensor,it's not important.However you connect it,it will work normally.

I don't know why you ask.These cars runs normally ONLY with OEM ECT sensors and oem ect sensors have oem connectors.