Cooling Fan running

Hi Victoria ,

1. Low coolant level in radiator.
2. Faulty fan relay.
3. Faulty secondary fan switch.
4. Overheating engine.

This has happened recently as the weather has got warmer. After engine shutdown the air con fan (the B fan I think) stays on. It eventually shuts off after 15 mins or so but even though this may be a helpful feature (built in perhaps) to help cooling after heavy running, 15 minutes of fan running after shutdown seems excessinve and is danger of taxing the battery I would think. The aircon refirgernat is charged ok, the car is kept cool with the air con on so everything with the aircon seems otherwise ok. The car engine temperature remains constantly within an acceptable range and does not overheat. Outside air temp is 23-25 degs celsius so we are not talking desert tempartures here. Any clues?

the fans are controlled by the PCM .. perhaps the temp sensor is the problem .. sending wrong signal to PCM

Hi lord farringdon,

Yup , I agree with Dave about the sensor.

Another possibility is shortage of coolant in the system.

Thanks for your responses guys. My mistake though. It's not the aircon (compressor ) fan which runs on but rather the radiator fan. My bad! Don't worry, I've already kicked myself up the backside several times for wasting your time on that one!! :)

The funny thing is when I checked the temperature gauge the first time this happened everything was normal, hence my earlier comments. Today the engine temperature was way up and the problem occured again when I shutdown. I was towing a lightly loaded trailer up steep hills at the end of my journey and the outside air temp was about 25 degrees celsius. Even so this operational profile has not caused this problem in the past so something is certainly different.

I checked the coolant as you suggested KHLow2008. The coolant is full, no leaks and the anti-freeze is in good shape. I wonder if the thermostat is playing up? I also wonder if I got the ratio of anti-freeze to water correct the last time I changed the anti-freeze? With the weather getting warmer the radiator may not be as efficient if there is too much anti-freeze. Have you heard of this problem occuring at 25 degrees C?

I will also follow the temperature sensor path as you have both suggested. I'll let you know how i get on.

Thanks for your help guys.

hello forum, my honda fans stop coming on, i have replaced two temp sensors and fan are brand new. However, when i turn the a/c on the fans come on no problem. I replace the lower radiator hose the other day and they stop coming on. i check fuses and the relays. I even let the car run for a whole hour before the temp guage was about to reach hot.can anyone help?

Thermostat?

Hi lord farringdon,

With a sore backside you won't be able to sit too long and enjoy a few beers to celebrate the New Year ;)

Towing would increase the temperature but the cooling fans should be able to handle it unless the cooling system is inefficient.

Possbilities of inefficient cooling are
1. Coolant, mixture out of specs
2. Thermostat, not opening sufficiently.
3. Clogged radiator
4. Weak water pump.
5. Clogging in other coolant passages.


HAPPY NEW YEAR

try radiator fan timer

Further to this problem:

Under standard driving conditions the cooling system operates normally but once I start to drive up any lengthy hill (say a kilometre or more) the car begins to overheat (temperature gauge goes from just above a quarter to 3/4) very quickly. If I turn the aircon off, the temperature slowly returns to normal even if still going uphill. If I drive the car without the aircon on, the car does not overheat regardless of operating on the flat or on hills. The problem has arisen since the weather in New Zealand has got hotter, although that might be co-incidence. (NZ is right hand drive, all distances are in kilometres and I think Accord in NZ = Acura in US).


Things I have noticed associated with the problem:

If I don't notice the temparture rise (as I said it happens quickly) my first indication is that the aircon looses its cooling effect like some sort of switch has recognised the need to automatically turn off aircon to help the engine cool itself.

If I turn the car off when it has overheated, the radiator fan comes on for several minutes after engine shutdown. I think this is what it should do to help cool the engine down.

Car Details:

Car: 1998 Honda Accord VTI-L 3.0 V6
VIN: 7A3CG1640WNVG 0066
ENG: J30A113385530
Mileage: 200,340kms


Things I have done so far:

When the problem occurs I have stopped the car, left the engine running, opened the bonnet and checked that both fans are working. No problems there, but of course I don't know if one or both fans momentarily did not work (causing overheat) then started again so that by the time I have stopped the car and checked under the bonnet that are happily spinning!. Due to the potential of expensive engine damage I am reluctant to continue to operate the car in the overheated condition just to just see if by chance the engine will cool again all by itself as a result of intermittent fan operation.

As explained above, the radiator fan also comes on after engine shutdown when the motor is overheated. In addition, I have noted the aircon fan starting with engine start (and aircon on). It seems the fans are both working as expected.

I have checked the coolant level at cold. Coolant is 50/50 antifreeze and has been relpaced recently. I can confirm the radiator is full to the neck and the header tank has fluid to the minimum mark. There are no leaks and the coolant level remained constant (no top ups required) before and after its replacement.

I have checked the radiator and condensor fins and there are no obvious signs of external blockage or damage that might affect cooling.

I have replaced the thermostat with an OEM part and have also replaced the water pump. I have noted the condition of the antifreeze which was very good and also the cleanliness of the internal passages at the water pump, thermstat and radiator filler neck entrances. There are no signs of any corrosion. I suppose there could still be an internal blockage but it seems unlikely given the shiny/clean nature of all the interanl passages I can see.


I have replaced the radiator cap with an OEM part.

I have replaced the fan control module and have also replaced the radiator and condensor fan relays.

The only items left to replace are the temperature control switches A and B and the engine coolant temperature (ECT) sensor although I think the ECT sensor is unlikley to be the culprit. I say this because the temperature gauge indications of engine overheating, seem to be supported by the fan going on after engine shutdown. The check engine light has not come on either which might be expected if the sensor was faulty. Am I wrong?

If the problem is with one of the temp control switches, which one is it likely to be? A or B and which one is A and which one is B. I don't want to replace more needless parts. Am I on the right track or is the overheating simply a sympton of something a miss in the aircon system? The engine remains at normal operating temparture with the aircon off so could this in fact be a problem with the aircon system for eg, might there be an internal blocakge in the condensor? Does refrigerant block condensor passages?

Thanks for the assistance so far.

Any further help would be most appreciated.


Regards


Terry

Hi Terry,

In US, Accord, Civic, Passport, Odyssey, CRV and Prelude are under Honda. Acura have Legend, Integra, TL, MDX and NSX.

The A/C would cut off when engine temperature exceeds a certain preset value.

The radiator fan is supposed to work at ignition off when the tempearture at the outlet of top radiator hose exceeds the preset switch temperature.

You do have an overheating problem and that is the reason the fan comes on after ignition switch is turned off. When engine ovrheats under strenous conditions, the cause is insufficient cooling. With the A/C on, there is additional strain on the engine and that would increase the heat produced by the engine operations, it should not be the cause. You have replaced most of the cooling system components so there are not many items left to check.

Since both fans are working, it should not be anything to do with the ECT sensor or fan switch, ( You have mistaken the ECT with the temperature gauge sending unit?) ECT fault would cause CEL or starting and performance faults. The Fan switch B is the one responsible for the fan operations at ignition OFF.

The sending unit is only an indicator for the gauge and it is working correctly since it is registering overheating, which is happening.

2 things that you should check.
1. Check for kinking of radiator hoses restricting coolant movement?
2. Did you check the radiator core for clogging? Did you drain off a little coolant from top of radiator and visually inspect the internal core for clogging? With A/C off, run engine till operating temperature and when fan comes on, feel the heat of the fan motor from various portion of the radiator. If any portion seems colder than the others, there could be partial clogging?

Did you use different brands of coolant for the system? Mixing of coolant would cause clogging of the radiator core.

Thanks KHLow2008 for the confirmations and clearing up of some of my statements.

Yes, I'm a little confused about the ECT versus the temperature sending unit. Are they two different sensors? Does the latter provide information for gauge readings and the former information to the computer? What can you tell me about "switch A" and "switch B". You say switch B is the one responsible for the fan operations at ignition OFF. Is that the switch near the thermostat? What does 'switch A' do and where is it located?

I have done as you suggested and checked to make sure there is no kinking or misalignment in the radiator hoses. When I had everything apart and coolant drained for the water pump and thermostat replacement I was able to see into the radiator filler neck and couldn't see any condition which even vaugally looked like rust or corrosion on the top of the fins. Coupled with the condition of visible surfaces and passages around the thermostat and the water pump, the general impression I got was a very clean water system. Still, one can't see much at all down the filler neck so one can only really make an educated guess based on what can be seen. So, I can't discount there might be something clogged in there. I will try your suggestion for feeling the temperarture of the airflow around the fans to see if that indentifies anything. In the meantime, anything you could tell me about the fan switches A and B (the only things I haven't replaced yet!) would be most appreciated. Are they immersed in the coolant or are they simply resting on metal and taking block temperatures?.

Regards


Terry

The engine is where the heat builds up and is the source of the heat. The fans won't come on unless they are asked to. So, I might suspect that the thermostat is faulty.

Hi Terry, Yes, you are correct about the functions of the ECT and sending unit. Switch A = On thermostat housing. Sends a ground signal to radiator fan control module when it heats up, at the same time activating the fan relay which would start the fan operations, when engine is running. Switch B = On front of left cylinder head. It operates at a higher temperature than Switch A and when it contacts, it grounds the fan switch B terminal in radiator fan control module when engine is not running. This would inform the radiator control module to send power supply to the radiator fan relay which operates when the PCM grounds the relay coil circuit. Both are immersed in the cooling system passages. I have attached a wiring schematic for your perusal as I believe the previous one could be for a different model.

Hi KHLow2008. Thanks for that schematic which makes much more sense than the first one. Thanks also for the A and B switch explanations. Frankly, this tells me that the switches are operating as expected by turning the fans on and off at the appropriate times. What more could I ask for!

All things considered, and with nearly all the parts in the system replaced it really looks like the radiator must be the 'core' problem (ok , pun intended).

I tried out your suggestion of checking for cooler or warmer portions of air coming from the radiator but it all just seemed universilly hot. In addition, as I stated earlier in the thread, I had "checked the radiator and condensor fins and there are no obvious signs of external blockage", but your suggestions have driven me to go back there again and look a bit harder.

There is very little space between the condensor and radiator, you can't even get your fingers down there. When I originally looked down there I was looking for the obvious obstructions like a plastic bag, newspaper or build up of leaves that would cause a severe restriction of airflow, but as I said there was nothing obvious. On your suggestion I have looked more carefully and have noticed what appear to be darker patches on the external fins covering about 30-40 percent of the radiator. An even closer look suggests these patches might be consistant with build ups of insects,grass,dust etc actually inside the fins. I can't be sure until I get the radiator out but there does seem to be some foriegn matter there alright.

So, I'm hopeful we might have found the problem. (fingers crossed). Now I can't do the job untill this weekend. In the meantime, if the radiator is in fact clogged in this way, what is the best method for cleaning those fins out once I have the radiator out? I have a small compressor but its old and pretty shot so I don't expect it to have much blow. Can I put the radiator in any kind of 'bath' to dissolve any buildup?

Thanks

Terry

Hi Terry,

You do not need very high pressure to get the grime or dirt etc off. Soaking it in a bath would be the best option but you must not use any substances that are too acidic. Dishwashing liquid would be a good choice for the soaking to soften the grime before cleaning.

Before soaking, use compressed air to clear off as much dust as possible to reduce the layers of dust.

We should be on our final stretch to victory.

Thanks KHLow2008.

I'll do the business this weekend and let you know early next week after I have taken it to work a couple of times, how I got on!


Regards

Terry

Hi and sorry to take so long getting back to you. I have attached a photo of the rear of the radiator and the front of the radiator. I could always see the rear of the radiator through the fans and so thought it was pretty clean. The very limited view of the front of the radiator by looking down the small gap between the radiator and the condensor also didn't suggest any problem. But, when I pulled the radiator back from the condensor preliminary to removing the radiator from the vehicle, boy did I get a shock! Anyway, cleaned the radiator as you suggested, reinstalled and road tested ok. Thanks for your time and patience. Much appreciated by this Kiwi! The first photo is the rear of the radiator while the second photo is the clogged up front.

Regards Terry

Hi Terry,

You are welcomed and thank you for the feedback. It would be valuable for future reference.

Glad that problem had been solved. Cheers.

I know the problem is resolved, but I decided to add one more thing to the discussion for future reference. In my 99 Accord Coupe V6 the fan switched on with the engine off even during cold days when the engine was nowhere close to overheating. The reason was air trapped in the cooling system. It worked its way to the top (the engine head) where sensor "B" happens to be located. It fooled the sensor so it switched on the fan for 10 - 20 minutes each time eventually leading to battery failure. While there may be a few reasons for air in the system, including serious (and costly) ones such as a head gasket needing to be replaced, in my case the explanation was very simple. The cause was that the little rubber hose dipped in cooling fluid inside the reservoir tank detached from the cap, to which a hose leading to the radiator is attached. When engine was cooling off and the fluid reduced its volume, it sucked in air, instead of the fluid from the tank. The air remained in the radiator and other parts of the system causing the problems described. I hope this post helps someone.

Cheers

That's good to know gdereck. That would be one of the last things I'd ever check if I had the problem again yet now it will be the first thing I'd check!

Terry.

Cooling system bleeding is something that is often forgotten when overheating or cooling fan issues are encountered.

When removing the radiator cap at cold engine temperature, the level should be at the top of the neck. While bleeding the cooling system, the heater should be turned to maximum to allow any air trapped in the heater coil to be expelled.

When any coolant depletion is discovered while no repairs had been carried out, system should be tested for leaks.

i am using honda accord coupe 1997 car for the past 12 years.i put up in kuwait and the temperatures here right now are as high as 50 degrees centigrade.i use coolant for the radiator.my query is that the radiator fan remains on even after the car engine goes off for arond 10-15 minutes?is this normal because im worried that this drains off my car battery....

This i feel will be normal in extreme temp conditions, you will have a problem if the fans keep running, as they shut down after the coolant temp falls to a lower level, this system sounds ok, you must remember that after the engine has shut off the coolant temp will rise as there is less cooling effect and the engine temp soaks into the coolant raising the temp, the fans running after shut down help drop the coolant temp quickly.

Just ensure the coolant level is correct and it should be ok as explained.

I have a 1997 Accord Wagon....runs great, have maintained it well, at least mechanically.

The odd thing happening lately is that AFTER I turn the engine off, a fan comes on under the hood. It doesn't ALWAYS come on, just every now and then. Sometimes it will come on after short drives (to the grocery), but will NOT come on after long drives (say 10-15 miles)...And while driving, I never see the temperature gauge start to indicate that the car is running hot....

Any ideas what this sound/fan could mean?

Might want to go ahead and replace the engine temperature switch-The fan coming on is normal but maybe the switch is out of calibration and its not reading on the temperaturre gauge.

Thanks boss....will look into that...makes sense - just seems that timing is off somehow...not a particularly hot motor, no smoke coming out, etc...

hello, i recently had my engine washed with some engine cleaner and pressure washed it , i got the engine nice and clean .. i did this round 9 at night ..after i parked it in the garage now its cold and snowy out here but its in da garage.... oh and i air hosed it dry ok .....now the next day i went to work and all was good ....i parked it in the parking lot ..after 10 hrs my shift was over and now i drive the car home now here when the problem starts........When i turn my car off the coolant fan still is going and the heater blower is on in the dash....where as before i turn the key off and everything is off ......ok the fan goes for a little bit thats normal and shuts off but now it just stays on... just stays on completely and the heater still has power li turn it off on the dash but still i can turn it on without the key ...i replaced the coolant relay switch so its not the relay ....and i checked the fuse and its not that so i just took off the fuse now all is off ......but i put the fuse in and everything is on .....so if someone knows whats going on with my coolant fan being possessed i surely would appreciate it ..thanks

Hi tiresmoke, Thank you for the donation. The blower motor receives its power from the blower motor relay in underdash fuse box. There is a possibility the relay is faulty and sticking causing it not to cut off when power is disconnected via the ignition switch. Try swapping the relay to see if it works.

your welcome ....but i found the problem out yesterday 1-9-10 surfing the net... because i didn't feel like waiting for a tech to answer back .....which im glad i didn't because that's not what the problem was ......the problem is ......when i read in another website ......is under the hood there"s an accessory relay or coolant relay on top of the right side of the radiator corner ....which there's two of them which i replaced it which cost for each one $32.00 and that was the answer to my problem.....the fan shuts off and the inside power is cut off the the ac/heat......so for any one else who has this problem as i did ...don't put all your eggs in one basket waiting for an answer ...do alot of research first which is free ...thank you anyways

Thank you for the input.

You are correct, the relay tends to short out when water gets to it, especially if the relay has detached themselves from the mount and becomes inverted. Water would collect and penetrate into the relay and cause it to short resulting in fans and blower to work.

When the car would not start and would not take a jump, my father discovered that there was a battery fuse that was burned out. We replaced the fuse and the car took a jump and starts fine but when you shut off the engine a fan continues to run. My father was able to disconnect this fan but we are not driving it in case overheating will result. I see from other posts that a faulty fan relay is often the cause for this. I am wondering if you would diagnose the same here and if so, can we replace this relay on our own or do we need to take it in to the garage?

Hi tlamberts, Yes, the problem seems to indicate a faulty relay and the replacement is simple which you can do it. Pull it out and plug in the new unit and it is done. However you should test if it is the cause first as the fan switch or it circuit if shorted to ground would cause the same problem. Turn ignition switch ON and pull out the relay, if the fans stops, replace with another and if fan does not operate, the relay is faulty. The power window relay is similar so you can try by borrowing from it to test. The diagrams I have is for a 2.2 liter and hope it is the correct one.

I just finished replacing the radiator and thermostat in my Honda accord. I believe I bled all the air out of the system through the coolant bleed valve by squeezing the hose, but I am not sure what is meant by "fill until a steady stream comes out". All I ever got was a dribble. The problem came when I hooked everything back up. The first thing I noticed is that the cooling fans didn't come on unless I turned on the AC. Upon further inspection, I found that the upper radiator hose was getting really hot and the lower one was hardly even warm to the touch. I figured it was the new thermostat I put in, so I replaced the old one (which I tested with the boiling water method and it was fine). The problem persists and I am unsure of where to go next. The relays were all working fine when I took the old radiator out.

The top hose is ALWAYS much hotter than the bottom, this is the water coming out of the engine to bee cooled in the radiator. The lower hose supplies the engine with cooled water If the fans don't come on they may not be needed at the temp the engine is at, or the ECT may be defective. But because they run with the a/c on means the fan is good...!

hello i hav a 96 honds accord and both cooling fans wont turn on.i thought i was getting poor coolant circ i changed the thermo and they still dindnt work. if you turn the ac on it doesnt work, i tried to test the resistance of the coolant switches and i get nothin.it seems like my engine is over heating but my guage reads normal on the cool side. wich if the engine isnt worming up the coolant enouph the switches wont hav resistance.other test ive done the relay in the fuse box is good i think. if you unplug the wire at the coolant switch b and jump the terminal with a wires the relay clicks but the fans dont com on. does this mean that the problem is from ther to the fan relay to the fan. the motors are good,also when you jump the green whire on the fan control box behind the glove box the fans do come on.or could i have a wirng problem or could an open ground couse this problem? thx

Sounds like the fan motor(s) have failed. Try applied direct power and ground to the fan. If they don't turn on, replace them.

[quote:408c5801df="F4I_guy"]Sounds like the fan motor(s) have failed. Try applied direct power and ground to the fan. If they don't turn on, replace them.[/quote:408c5801df] i have tested the motors ther good both of em did you read the whole post i jumped the wires at the fan control box behind the glove box and the fans came on when you jump the wires at the coolant temp swith you can here the relay under the hood fuse box click but the fans dont come on so should the fan relay on the side of radiator click and turn the fan on or is it electrical

i have a 1995 accord ex that had a blown motor when i bought it. i put a new motor in with new radiator and fans. neither fan comes on with the ac on or off. the fuse inside is good and the cooling fan relay is good. my repair manual mentions other relays, but is not clear on their location or how to test them. help?