Cooling Fan running

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?

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?

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

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

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

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

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