# Rad Fans Stay On??



## Max96 (Aug 25, 2005)

Just grabbed an '00 Altima with 56k today. Only thing I notice is that after driving for a few minutes the radiator fans, both of them, come on and stay on. They stay on for approximately a minute after I turn it off also. Its around 45degrees today, most of my driving is highway. This should definitely not be happening. I cant find any leaks, nothing boiling into the reservoir tank, temp guage normal, no clue why. Anyone had this same problem? Any idea how to fix?


----------



## Asleep (Jan 19, 2003)

its actually quite normal. not everyones altima does it but that doesnt necessarily mean that yours is bad. the coolant temp sensor could be a bit weak, but otherwise, you should be ok.


----------



## Matt93SE (Sep 17, 2003)

several issues it could be.. here's what I'd check first:

1. is your A/C or defrost on? the fans run all the time when the A/C is running. defrost also fires up the A/C to remove the moisture from the air and clear the windows quicker.

2. damaged/disconnected water temp sensor or wiring. when the sensor is disconnected or fails, it goes to an open circuit, which the ECU sees as infinite temperature. it then turns both fans on high to attempt to bring water temp down.

3. air in coolant system. bleed system according to FSM to remove air bubbles trapped in the engine and hoses.


----------



## Max96 (Aug 25, 2005)

Thanks crew... bought a Hanes manual, did some research, looks like it the sensor that works with the ECM to start/stop the fans. Gonna grab me a new sensor on Monday.


----------



## Matt93SE (Sep 17, 2003)

check the connection on it first.. often they get green and corroded from moisture in them. clean it up and mash some dielectric grease in there and see how that does.


----------



## Max96 (Aug 25, 2005)

Matt93SE said:


> check the connection on it first.. often they get green and corroded from moisture in them. clean it up and mash some dielectric grease in there and see how that does.


Cool... excellent info. Gonna go out and do that now. Thanks again for all the advice.


----------



## Max96 (Aug 25, 2005)

Changed it with a new one... no help. Gonna change the thermostat next.


----------



## Asleep (Jan 19, 2003)

if the thermostat doesnt help - bleed the system well and then dont worry about it. if youre not boiling over and the fans are staying on for no more than a minute or so, its normal - i wasnt bullshitting you, lol.


----------



## Max96 (Aug 25, 2005)

These F-n fans stay on ALL THE TIME after it hits operating temp. Insane...


----------



## Asleep (Jan 19, 2003)

even with the car running then, huh? now THATS not normal... coolant temp sensor should be checked then as well. its the sensor behind the power steering pump on the intake manifold. check it for condition and then check the resistance against what the manual says for it. btw, go here for an fsm for your vehicle - www.phatg20.com the fsm is a very valuable thing to have when you are working on your car. be sure you dont remove the coolant temp sensor though if the engine is hot, you will get sprayed with burning hot coolant.


----------



## Asleep (Jan 19, 2003)

i think thats the sensor you just replaced... i didnt realize thats the one you did... read my pm, that will help point you in a direction as well.


----------



## Max96 (Aug 25, 2005)

Replaced the sensor, replaced the thermostat, still F-d up. The bottom hose going to thermostat never gets hot which means a stuck thermostat, not true, I changed it. I am sooo frustrated. Driving the Pathfinder until the weekend when I can pull the radiator and check for flow and then possibly run the car without the thermostat just to see of the bottom hose even gets warm. Someone just kill me.........


----------



## Asleep (Jan 19, 2003)

you can also check flow by touching the different areas of the radiator till you find a spot that is noticeably cooler than the rest of the radiator.


----------



## Max96 (Aug 25, 2005)

All fixed... (I think) Checked radiator, all clean and good, water pump was pushing water through, all good. Couldnt figure out why when driving this F-n thing would run with the fans on all the time. I pulled the thermostat, and ripped out the air bleed thingy and enlarged the hole a bit with a drill to allow a tiny bit more flow while thermostat closed. Looks like it worked, drove it for around 20 min on highway and fans never came on yet it reached normal operating temp and heat was working just fine. Even after pulling into driveway, fans not on. Fixed I guess...  I went so far as to let it idle and watched fans come on and off as it got hot. Also verified fan functionality with AC on. Driving to work later, this will be the final test...


----------

