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Radiator fan

Tiny
JACG21
  • MEMBER
  • 1999 HONDA CIVIC
My relay, fuse, coolant temp switch, and fan motor are good. Why wont my radiator fan motor still not turn on at the appropriate time?
Saturday, September 6th, 2008 AT 11:31 PM

40 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Could be the coolant temperature sensor or computer not getting the correct signal from the sensor or the switch therefore not activating the relay or a thermostat that is not controlling the engine temperature.
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Sunday, September 7th, 2008 AT 3:10 AM
Tiny
REDDRAGUN3
  • MEMBER
  • 2 POSTS
  • 1999 HONDA CIVIC
  • 4 CYL
  • FWD
  • MANUAL
  • 170,000 MILES
I just recently installed a complete AC unit from another used 99/00 Honda civic. Also, the radiator was fixed and replace a month before that. Now, when I turn on the AC, the temperature immediately raises up and my car overheats. My mechanic told me that the radiator fan turns off when the AC fan turns on. I can hear the radiator coolant boil and see steam come when I park the car after driving home from work (18 miles) The car also looses coolant after a month or so. I believe this was due to me turning on the AC and not noticing the temperature rise up. I think there might be a leak somewhere but there is no puddle under the car. It might be burning up before it hits the ground. Please help.
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
Hi reddragun3,

Did you check if the radiator fans are working?
If what your mechanic mentioned is correct about the radiator fan turning off when the A/C is turned ON, you have a wiring fault. Check the fuses in underhood fuse box first.

When coolant is depleting, there must be a leakage somewhere. Get a pressure test done to locate the source.
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
REDDRAGUN3
  • MEMBER
  • 2 POSTS
Hi KHLow2008,

Thanks for the reply. The fans are working just not together. I figured that there would be a wiring fault I just didn't know where to start. I'll take you advise and start with the fuse box under the hood. I'm not sure where to get cheap replacement parts for those relays on the right side (small black cube things) but I'm sure I'll find something with a little research online. Or maybe the honda dealer if I get desperate.

The leakage is killing me? I can't find it. Do you know where I can get a pressure test. Maybe my mechanic can do it? Not sure. But I will try this weekend and hopefully have some good news to post. I very happy and grateful someone just answered my post. It was looking hopeless for me. Now I have a direction will do my best to tackle it this sat/sun. 1 more day I guess without AC. I'll post the outcome. Thanks again.
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
KHLOW2008
  • MECHANIC
  • 41,815 POSTS
For manual transmision, the radiator and condenser cooling fans do not work together.

The radiator fan would not turn on until the fan switch operating temprature is breached. There is nothing wrong with the system.

Your mechanic should be able to perform a pressure test.

When engine is cold, check the coolant level in radiator. Top up if necessary.
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
HONDAGRL
  • MEMBER
  • 1 POST
  • 1998 HONDA CIVIC
Engine Cooling problem
1998 Honda Civic 4 cyl Wheel Drive Type unknown Automatic 150000 miles

I just changed the radiator in my car, I was just wondering why the radiator fan is not working?
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
RUMBLEFISH_2
  • MEMBER
  • 2 POSTS
I too have just replaced my radiator, but it doesn't seem like the fan is working. I filled the radiator with coolant and left the cap off like the Haynes manual said, then ran the car for a while. The coolant starts to smoke (or vaporize) after a while but doesn't not seem to be moving through the system. The radiator fan never kicks on either. The top radiator hose gets hot, so the thermostat is open right? Why is the coolant not cycling and why won't my fan come on?
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
JASTIDHEERAJ
  • MEMBER
  • 1 POST
  • 1997 HONDA CIVIC
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 135,000 MILES
My probelm is, my engine gets hotter when I am stuck up in the traffic. I know that the problem is with the cooling fan, so I have replaced the thermostat, relay, sensor, stiill the probelm continued. So I got the fan changed also but still the problem continues. The cooling fan on the radiator turns on sometimes and it does not turn on sometimes. I have also checked the coolant level and it is good. Previously when I got this problem 6 months ago I got rid of it when I changed the sensor but this time I could not rectify it. Please help in this matter. Thank you.
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
MHPAUTOS
  • MECHANIC
  • 31,938 POSTS
If all the components are in good working order, start looking at a faulty loom plug somewhere, try bridging out the sensor to stat the fans, and try flexing all the plugs at the fan and sensor, it may be a faulty pin connector in a plug.
Mark (mhpautos)
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
DUNKINDANNY
  • MEMBER
  • 2 POSTS
  • 1996 HONDA CIVIC
I have a problem I fix my radiator I put a new fan on it but the fan is not working. But I test out the fan to the baterie and it works and I put a new sencor to the engine which is for the radiator. And the fan still does not turn on what could it be.
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
BRUCE HUNT
  • MECHANIC
  • 3,753 POSTS
There are fuses and relay. I am sending you a copy of the electrical diagram for the cooling fans including the fan for the A/C condensor.
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
DUNKINDANNY
  • MEMBER
  • 2 POSTS
When are you sending the electrical diagram for the cooling fans including the fan for the A/C condensor.
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
BRUCE HUNT
  • MECHANIC
  • 3,753 POSTS
Sent it right away yesterday. You should have gotten it by now.
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Friday, August 9th, 2019 AT 5:48 PM (Merged)
Tiny
HONDADUDE
  • MEMBER
  • 1 POST
  • 1995 HONDA CIVIC
Having a problem with overheating in traffic for the past few months. Some leakage around the top of the radiator noticed just recently. Cooling fan not turning on while stopped. Thermostat just replaced. No "bubbling" in the radiator or evidence of oil in radiator or anti-freeze in oil. Any ideas?
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Friday, August 9th, 2019 AT 5:49 PM (Merged)
Tiny
BRUCE HUNT
  • MECHANIC
  • 3,753 POSTS
Sounds like the fan or more likely the sensor for the fan. Try shorting the fan directly to the battery to see if it runs. If so and the wiring seems fine you can replace the sensor for the fan, not the temp sensor around the thermostat. Another option I have seen done is to just let the fan run all the time the engine is on. Works as well. Try the motor test and then make your call on replacing the sensor.
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Friday, August 9th, 2019 AT 5:49 PM (Merged)
Tiny
EJACKSON23
  • MEMBER
  • 2 POSTS
  • 1995 HONDA CIVIC
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 30,028 MILES
My car leaks water/radiator fluid from the resevoir when the car is driven for a while. The fan not attached to the radiator comes on when I turn the A/C on but the fan to attached to the Raditor does not come on. I have replaced the fan motor but the fan attached to the radiator still does not come on. The temperature guage in the car doesn't show that the car is overheating but I can see what dripping below. How can I get the fan attached to the radiator to come on so that the car doesn't over heat causing fluids to over flow to the resevoir?
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Friday, August 9th, 2019 AT 5:49 PM (Merged)
Tiny
F4I_GUY
  • MECHANIC
  • 3,302 POSTS
It sounds like you have two issues.

1)the fan, it's common to have to replace the fan switch on these vehicles, however, I would definately check for a blown headgasket first before trying to diagnose a cooling fan issue.

2)a blown headgasket. This is what is causing the fluid to over-flow/bubble or be pushed out of the resevoir. The blown gasket is allowing excess pressure into the radiator, thus pushing the coolant out.
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Friday, August 9th, 2019 AT 5:49 PM (Merged)
Tiny
EJACKSON23
  • MEMBER
  • 2 POSTS
F4I_Guy, Thanks for the reply. I think the head gasket might be the issue is there anything I can do in the mean time until I can get the head gasket fixed?
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Friday, August 9th, 2019 AT 5:49 PM (Merged)
Tiny
SLUG2FACE
  • MEMBER
  • 2 POSTS
  • 1995 HONDA CIVIC
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 104,000 MILES
My radiator fan will not work, making my car overheat. Its not leaking, I put a brand new radiator and water pump and the three belts that are on the right side of the motor, I put all three new, I also put a new thermostat, I dont know how to check this, please help with this question
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Friday, August 9th, 2019 AT 5:49 PM (Merged)
Tiny
BRUCE HUNT
  • MECHANIC
  • 3,753 POSTS
You can test the radiator fan by wiring it direct to the battery. I would suspect that it is fine and the issue will be with the temp sensor that activates the fan. Also, since the work was done it might be nice to check the system to make sure the air is out of it. Purge the air from the system with the engine warm and running by cracking open a bleeder.
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Friday, August 9th, 2019 AT 5:49 PM (Merged)

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