radiator fan

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.

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.

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.

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.

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.

Engine Cooling problem
1998 Honda Civic 4 cyl Wheel Drive Type unknown Automatic 150000 miles
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I just changed the radiator in my car, I was just wondering why the radiator fan is not working?

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?

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...

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)

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...

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.

when are you sending the electrical diagram for the cooling fans including the fan for the A/C condensor.

Sent it right away yesterday. You should have gotten it by now.

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?

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.

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?

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.

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?

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

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.

Where is the bleeder and the temp sensor located? Thanx I feel better that. U guys are helping me.

Follow the big radiator hoses and you will find a little nipple that takes I think an 8mm wrench. If the fan runs one of these sensors shown is possibly bad. I wouldn't just rush out and replace them. Bleed the system first and then if you have and know how to work an ohm meter I can tell you how to test the sensors.

Engine Cooling problem
1993 Honda Civic 4 cyl Front Wheel Drive Automatic

1993 Honda Civic DX
Radiator cooling Fan will not come on, replaced
everythng possible including radiator. Straight
wired from the fan to the cooling fan switch
in the breaker box and the fan comes on.

Check the coolant temperature sensor or the engine temperature guage sender/switch to include the fan relay-

Already reaplaced the cooland temperature
sensor too

Check the engine temperature gauge sending unit on cylinder head near water outlet cover-if its okay could be the computer that's causing it-

Engine Cooling problem
1994 Honda Civic 4 cyl Front Wheel Drive

If the fan for the radiator is not turning on, is there a way to tell if it's the fan or just the relay?

You can put power and ground straight to the fan motor, if it turns on, the fan motor is fine.

You may also jump the fan switch at the thermostat housing. if the fan comes on, you verified everything in the system is operating properly, except the fan switch.

what could be the problem? we purchased the car used and realized that when the fan came on there was a grinding sound, then the grinding didn't come back for about a week. I am not sure if the fan is coming on at all. Now the car is overheating after only 5-10 minutes on the road. We checked the coolant, and put some in, but it is still overheating excessively (all the way to the red).

Hi OchicabebeO,

When the temperature goes up, you should check if the radiator fans are working.

turn AC on and if fans don't work, you need to test notor and replace if necessary. The noise is normally from a failing fan motor and could have failed already.

My radiator cooling fan will not start, but will turn on if jumped.

It's a pretty new radiator, new hoses, new thermostat, and I just replaced the Relay hoping that would fix the problem.

Another thing I noticed, while the car is over heating, the top hose will be hot, but the bottom hose stays cool.

My car has over heated many times and more than likely the head gasket is ruined, but I'm not sure how else to check (my oil looks clean.)

Any thoughts or ideas on what to check now? And you should know... I really don't know anything about cars!!!

Cooling fan not coming on could be either a defective coolant temperature sensor or the engine temperature gauge switch to include the computer.

Overheating: Could be a radiator clogged-up, defective water pump and air in the system if all okay get it block and pressure tested to rule out a blown headgasket cracked head or block

Air Conditioning problem
1995 Honda Civic 4 cyl Manual
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I have a 1995 Honda Civic 5 speed 4 cylinder, The radiator fan, conditioning fan, a/c compressor won't come on. Do you have a suggestions?

Hi GlennGrammer,

Being a manual version, the radiator fan would only work when the fan switch is activated as the coolant reaches operating temperature. Test the fan relay for power supply to fan motor and test if motor is ok.

If Ac compressor is not working, the condenser fan would not come on.
You need to check if there is enough freon in the system.

I have a 91 Honda Civic si hatchback 1.6L. It has 270,000 miles with 30,000 on a rebuilt engine.

My radiator fans are not coming on. I believe this is what is responsible for the crack that is now on the upper plastic part of the radiator. I have runs wires from the fans to the battery and they come on fine. I have attached a jumper wire to the thermo switch going into the radiator and the fans still failed to come on when the car was turned on. The fans come on when I turn on the air conditioner.

Could the problem be another thermo switch or one of the relays?

Thanks for your help

First of all the A/C will kick on the right fan to cool its own system. This should not turn on the engine coolant fan. There is more than one sensor for the engine coolant system. You have tested the fans as I would have suggested. Without assistance of wiring diagram one of the sensors I think is located near the radiator and the other is located next to the thermostat. I would say that one of those is not functioning properly.

Hello,

I have a Honda Civic EX 4 cyl with 200K miles. I had the radiator replaced after the old one cracked. A few weeks after that I noticed the temperature start to heat up after I was driving it for approx 1/2 hour and slowed down. When I came to a stop and popped the hood, I noticed the cooling fan wasn't running. Another time after I popped the hood when I stopped, the cooling fan ran for about 5 seconds and then cut out even though the temperature was high. It's frustrating getting it fixed because it doesn't seem to do it when the car is cold. Twice I have had it in and the fan comes on when they test it. $150 later and I still have the same problem. It's driving me nuts, what could it be?

Sounds like a short in the wiring.

Try a new fan temp switch.

Hi guys! just want to add something
Two components control the fan:
The thermal switch jack had mentioned and the fan relay.