# Radiator fan not coming on......



## Laura147026 (Jun 9, 2003)

HELP!!!

My fan is not coming on. I haven't done anything yet because it only heats up in idle. I don't idle much. I want to see if you guys could give me a cheapest to most expensive reasons. I want to start with cheap and see what happens. A friend of mine told me to hot wire it to the battery so it comes on when I start the car but then it would run too cold sometimes. Let me know what you think......Laura


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## James (Apr 29, 2002)

Try wiggling the connectors on the fan... might be just loose.


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## Laura147026 (Jun 9, 2003)

James said:


> Try wiggling the connectors on the fan... might be just loose.



I will try that again..I did it when I first noticed it but it was dark. The wires are original, dirty and old. I will give it another chance before I start taking things apart....Thanks...


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## Gsolo (Sep 11, 2003)

Laura147026 said:


> I will try that again..I did it when I first noticed it but it was dark. The wires are original, dirty and old. I will give it another chance before I start taking things apart....Thanks...


is it overheating at all???


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## Popkorn (Nov 16, 2003)

Mine would only come on after idleing for 5 mins or so. The gage gets just a hair over 1/2 then it clicks on. The fan has a temp sensor in the radiator and a relay as well as a fuse. You can disconnect the fan and put 12v on it direct from the battery (for a fan test)


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## Gsolo (Sep 11, 2003)

Popkorn said:


> Mine would only come on after idleing for 5 mins or so. The gage gets just a hair over 1/2 then it clicks on. The fan has a temp sensor in the radiator and a relay as well as a fuse. You can disconnect the fan and put 12v on it direct from the battery (for a fan test)



thats when the fan is suppose to come on...although i'll admit the gauge is probably about 30degrees off at any moment


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## Popkorn (Nov 16, 2003)

Gsolo said:


> thats when the fan is suppose to come on...although i'll admit the gauge is probably about 30degrees off at any moment


Well, yea. I dint say it had any probs. Just givin Laura a scenario of what these cars act like. She might be overreacting. Even on the hottest days of summer, the fan only kicked on after a long idle. (Hottest days of summer in OR = typical day in FL.)


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## Gsolo (Sep 11, 2003)

Popkorn said:


> Well, yea. I dint say it had any probs. Just givin Laura a scenario of what these cars act like. She might be overreacting. Even on the hottest days of summer, the fan only kicked on after a long idle. (Hottest days of summer in OR = typical day in FL.)



thats what i was trying to back up on. i've only had my one fan on, dont think it's ever gotten hot enough to turn on the second fan. .....althogh dual fan is only on pulsar huh


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## Popkorn (Nov 16, 2003)

Gsolo said:


> i've only had my one fan on, dont think it's ever gotten hot enough to turn on the second fan. .....althogh dual fan is only on pulsar huh


THe second fan is supposed to kick on when when the AC is engaged. Sentras' have 2 fans only if they're equipped with AC.


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## Gsolo (Sep 11, 2003)

Popkorn said:


> THe second fan is supposed to kick on when when the AC is engaged. Sentras' have 2 fans only if they're equipped with AC.


that makes sense.......i haven't used the a/c yet, tried once but it needs charged again.


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## Laura147026 (Jun 9, 2003)

Popkorn said:


> Well, yea. I dint say it had any probs. Just givin Laura a scenario of what these cars act like. She might be overreacting. Even on the hottest days of summer, the fan only kicked on after a long idle. (Hottest days of summer in OR = typical day in FL.)



I'm not overreacting. It overheats and doesn't come on. I am probably underreacting. I will try the hot wire to the battery to check the fan motor itself. That was helpful advice....Thanks to all...Laura


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## Popkorn (Nov 16, 2003)

Laura147026 said:


> I'm not overreacting. It overheats and doesn't come on. I am probably underreacting. I will try the hot wire to the battery to check the fan motor itself. That was helpful advice....Thanks to all...Laura


Laura, you've come to the right place for help. We could use a little more info. When you say it overheats, is it the gage telling you it's too hot or does it actually boil coolant out the overflow? It could be something simple like a radiator cap or a stuck thermostat. Could be something $$$$ like a headgasket starting to go. Check under the oil cap for milk. Also, since you're close to the coast, check to see that your radiator does'nt suffer from electrolosys. I had one you could put your finger right through it.


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## James (Apr 29, 2002)

If you have DSL or some sort of high speed connection check here for a full copy of the FSM. In there you can find how to test for pretty much any problem but specifically you can find how to use an ohmeter and test the fans.


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## Laura147026 (Jun 9, 2003)

Popkorn said:


> Laura, you've come to the right place for help. We could use a little more info. When you say it overheats, is it the gage telling you it's too hot or does it actually boil coolant out the overflow? It could be something simple like a radiator cap or a stuck thermostat. Could be something $$$$ like a headgasket starting to go. Check under the oil cap for milk. Also, since you're close to the coast, check to see that your radiator does'nt suffer from electrolosys. I had one you could put your finger right through it.



The gadge tells me and the radiator water boils. The only time it overheats is at the lights. When I'm moving, it's cool. The radiator is not that old, so I know that's not the problem. I just had the sensor replaced for the gadge. I will check the thermostat but why would that cause the fan not to come on? I understand it would cause the overheating but why would it stop the fan from kicking in? 

I have been using the A/C fan to help cool the engine too. 

Thanks...Laura


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## Gsolo (Sep 11, 2003)

Laura147026 said:


> The gadge tells me and the radiator water boils. The only time it overheats is at the lights. When I'm moving, it's cool. The radiator is not that old, so I know that's not the problem. I just had the sensor replaced for the gadge. I will check the thermostat but why would that cause the fan not to come on? I understand it would cause the overheating but why would it stop the fan from kicking in?
> 
> I have been using the A/C fan to help cool the engine too.
> 
> Thanks...Laura


if the stat doesnt open up to let the hot water into the radiator, although i've never heard of it happening i'm sure its possible


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## WhiteFox (Sep 4, 2002)

It could also be your fan relay has burned out.. or is missing.. or whatever..

Check that.


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## Popkorn (Nov 16, 2003)

Laura147026 said:


> The gadge tells me and the radiator water boils. The only time it overheats is at the lights. When I'm moving, it's cool. The radiator is not that old, so I know that's not the problem. I just had the sensor replaced for the gadge. I will check the thermostat but why would that cause the fan not to come on? I understand it would cause the overheating but why would it stop the fan from kicking in?
> 
> I have been using the A/C fan to help cool the engine too.
> 
> Thanks...Laura


hmmm
if your thermostat is stuck closed, the water in the block and head will get too hot/boil and it will show on the gage cuz the sensor is on the engine. But the water would not get hot enough for the sensor to activate the fan relay. But, since the ac fan cools the water, I don't think that's the prob. There is another sensor on the radiator that kicks on the fan when the water in the radiator gets too hot. Think I have a used one you can have. New was like 28 bucks and it didnt fix my gage that faked me into thinking it was over heating. So it should be good. But first try putting 12 volts directly to the fan to make sure it's still good. PM if your interested in the used sensor.


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## Gsolo (Sep 11, 2003)

Popkorn said:


> hmmm
> if your thermostat is stuck closed, the water in the block and head will get too hot/boil and it will show on the gage cuz the sensor is on the engine. But the water would not get hot enough for the sensor to activate the fan relay. But, since the ac fan cools the water, I don't think that's the prob. There is another sensor on the radiator that kicks on the fan when the water in the radiator gets too hot. Think I have a used one you can have. New was like 28 bucks and it didnt fix my gage that faked me into thinking it was over heating. So it should be good. But first try putting 12 volts directly to the fan to make sure it's still good. PM if your interested in the used sensor.


ummm....the water in the block can easily set off the fan relay...you're looking at least 220F if its not cooling right.


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## Gsolo (Sep 11, 2003)

heres my thought on what i would do....first check fan by hot wirring it....and unplug normal wire from fan first just to insure you dont blow out something. if the fan works then you got to check the wiring and relay. i think the culprit is the relay more than anything. if you're sure there is hot water in the radiator than the thermostat is probably workin......and a way to keep your car from overheating to bad is leave the heater on full blast.


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## blownb310 (Jun 10, 2002)

Hi all,
I remembered a thread just like this from a while back. I simply clicked on search, typed in "cooling fan relay" and bingo, there it was: http://www.nissanforums.com/showthread.php?t=25569&highlight=cooling+fan+relay
I have cut and pasted my reply here from that thread. Hope this helps Laura!







Now I know some of you already mentioned the cooling fan relay, but no one told Laura where it was, what it looked like, or how to test the fan motor. 

*From May 2002:*
All of the suggestions in regards to flushing and a new thermostat are good ideas before you proceed. If you still have a problem after that, you might check your cooling fan relay for corrosion. The relay is mounted on the driver's side of the engine compartment, on the radiator support, right by the battery. It will be a blue relay that is snapped into a holder. I have repaired my winter beater B12's cooling fan by replacing this corroded relay with a good used one from a parts car. I spliced in the entire connector too, because the old one was full of green corrosion. 

Additionally, if you want to verify that your cooling fan motor is good, simply pull off the two wire connector at the radiator temp sensor [that you already checked out]. Turn the key to the "on" position, and jump the connector with a paper clip on the engine harness side of the connector you pulled off. The fan should run immediately. If it does, go to the relay I mentioned above.


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## SuperSentra4203 (Dec 17, 2002)

If the fan motor is good, just wire a Bosch 40amp relay to a toggle switch. That way, you can control your cooling fan whenever you want


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## 50dollasentra (Jan 11, 2004)

Ok i didnt read all tha replys but if you are runnin a GA16i there is a lil sensor some where near the water pump. It has 2 lil wires runnin frum it, aint hard to miss. well anyway it controls the fans and crap. The wire on mine broke and needed to be replaced. But i had to run around with the a/c runnin so the fans wood run too. SO you shood check that b4 you check anything else!


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## 50dollasentra (Jan 11, 2004)

50dollasentra said:


> Ok i didnt read all tha replys but if you are runnin a GA16i there is a lil sensor some where near the water pump. It has 2 lil wires runnin frum it, aint hard to miss. well anyway it controls the fans and crap. The wire on mine broke and needed to be replaced. But i had to run around with the a/c runnin so the fans wood run too. SO you shood check that b4 you check anything else!


DAMN I KNEW I SHOULD HAVE READ THE WHOLE THING!! dont tell me i didnt read it! THATS HOW LAZY I AM LOL!!!


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