cooling fan

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90 accord 4cyl. Cooling fan doesn't always work. Causing heating problems. Any ideas?

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On 3/4/10 11:34 AM, in article AOWdncGuPqPQchLWnZ2dnUVZ snipped-for-privacy@neonova.net,

Doesn't always or doesn't ever? Makes a difference. Does it always come on with the AC?
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ac fan works fine(seperate fan).radiator cooling fan works about half the time.
wrote:

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On most Hondas, they both come on with the AC. If it works some of the time, the first thing I would check is that the radiator is full.
I have to ask though, how do you know when it should come on but doesn't (given that its not supposed to run all the time)? What are the other symptoms?
On 3/4/10 1:56 PM, in article 0q-dnTsGC6P7jQ3WnZ2dnUVZ snipped-for-privacy@neonova.net,

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Engine heat mostly when idling. Coolant fine. Does this model have a timer? I just heard it come on. Ran for about 30 sec's or less.
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It's not likely the timer. Your problem is most likely the thermo switch in the water jacket.
Disconnect the wires at the switch and short them together. Rad fan should run continuously. If it does, the thermo switch needs to be replaced.
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CLARIFICATION: This should be done when the engine has warmed up to the point when the fans would be on anyway (~205F at the upper rad hose inlet).
Also, your model may have the thermoswitch in the bottom of the rad, so check there too.
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I am not sure the guy actaully has a problem. He said the fan came on. He probably should define "heating problems." The fans aren't suppose to run all the time when the A/C isn't on.
BTW, I don't know of any cars that have a "timer" on the electric cooling fan. All that I am aware of have thermostats (as you mentioned). Some are single stage, and some are two stage (either running the single fan at two different speeds, or running multiple fans as needed). Some cars also have switches in the A/C lines to turn on the fan(s) as needed for the A/C instead of merely running them whenever the A/C is switched on.
I think the first stage in helping this guy is learning what he meant when he said "Cooling fan doesn't always work. Causing heating problems." Is the car actually overheating, or does the gauge just move up the scale but stay in the "normal" zone? The fans are not suppose to always be on.
Ed
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Some Accords have one. It's used under certain conditions to run the fan for five minutes AFTER the engine has shut down. When the timer fails, the fan will not run after the engine shuts down.
This generation of Accord normally has trouble with the thermoswitch itself, or with the relay. If the relay is bad, shorting the thermoswitch wires will not make the fan run. Provided the engine is fully-hot to begin with, that is.
Thermoswitches can fail in five ways: 1) failing to turn the fan on at all, 2) running the fan all the time, 3) turning on the fan too late, 4) turning the fan on too soon, 5) shutting the fan off too soon.

That's a good point. OP should report the position of the temperature gauge needle when the problem is occurring. I assumed he meant the engine was overheating at idle.
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Tegger wrote:

My 1995 Accord does this. Do you know why this is? I have never seen a car that runs the fan after being shut off before and I can't imagine any reason for additional cooling after turning off the engine. That seems like the last time that a fan is needed.
In less than 6 months of driving it, I have had at least 3 people tell me that I left the car on when they heard the fan running, and when I told them that it is just the fan, that confused them as they also can't see a reason for it to be designed this way.
It is irritating enough that it has had me thinking about figuring out a way to make e fan stop coming on after turning off the engine unless there is a good reason for it.
Thanks!
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On 3/5/10 9:36 AM, in article hmr8dp$amd$ snipped-for-privacy@speranza.aioe.org, "pws"

Nothing new. My '79 VW Rabbit did it. I remember most cars were capable of running the radiator fan after the engine shut down in the first few years after transverse engines got popular and electric radiator fans came into common use.
It sorta makes sense, since the engine temperature will go up when its shut down and the coolant stops circulating. New cars don't seem to do it anymore, probably a few too many missing fingers & lawsuits...
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E. Meyer wrote:

I figured that some other cars did it, but it is rare enough that I have never seen it before, and most of my cars have had electric fans.
I would still prefer that it did not do this, but doubt if I will put the effort into making it stop. I have been very good at leaving this car alone except to maintain it.
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On 03/05/10 13:55, E. Meyer wrote:

Bingo, I had a '79 Rabbit as well.
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Actually the runtime is 15 minutes, not 5. I was misremembering in my last post. Also it only kicks in if coolant temp is above about 223F.
The reason for this is that when you shut the engine off, all fluid flow stops. This causes a heat-soak condition that can make block temperatures spike quite a bit (to 223F and above). Heat-soak is a bad thing.
Post-shutdown fan operation does two things: 1) it cools the block and head surfaces with its air flow, and 2) it creates a coolant thermosyphon effect that help lower temperatures inside the block and head. These two together help minimize the damaging effects of heat-soak.
Do not disable post-shutdown fan operation, as annoying as it may be.
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Tegger wrote:

Gotcha, I will not do anything to disable this, but......this does bring up another question or two.
My other car, a Mazda, has an aftermarket turbo setup and runs pretty hot during the summer despite an upgraded aluminum radiator. The exhaust temperature gauge on that car moves up and down almost like a speedometer needle once it has warmed up.
Would this car benefit from having a device installed that runs the fan after turning it off? I am guessing that it runs hotter than the Accord since the turbo gets so hot.
My other question is why all cars with electric fans versus mechanical do not do this.
Thanks!
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On 03/06/2010 05:36 AM, pws wrote:

of course - the pans on your stove boil more vigorously when you turn up the flame.

it might well, but not necessarily enough to make the fan worth while. the turbo is designed to run hot - it wouldn't benefit* and the motor should be something the design team have already mapped.

because it's not necessary. it also depends on the coolant flow design. if you notice, the radiator coolant flow on a honda is still top-to-bottom. this gives a component of thermosiphon just like tegger says. no need for a fan after shutdown.

* - the turbo bearings benefit from not getting heat soaked, but a fan wouldn't necessarily prevent this, though it might shorten it. with a turbo, it's best you do two things:
1. run the motor at idle for a minute or two before shutdown. [some turbo diesel truck engines i used to work on has a three-minute-idle-before-shutdown s.o.p.]
2. use synthetic oil - it's more heat resistant.
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jim beam wrote:

Thank you for the clear answers. I have used synthetic oil as did the person who built the car, and I do let it run a bit before shutting it down, that is what he recommended as well.
When I got the car, I did not understand turbos at all. I thought that the car was running hot and used an thermometer on it that went to 500 degrees Fahrenheit. When it went over max and tripped the thermometer I though that the engine was history, I had no idea that turbos produced that kind of heat.
Now I need to get the blowoff valve installed.
Thanks again,
Pat
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pws wrote:

Make that, when I used a thermometer on the turbo itself, it tripped the thermometer. The engine was considerably cooler.
Pat
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On 03/06/2010 11:11 AM, pws wrote:

it's sitting in the exhaust gas stream, so you would expect the turbo to get warm. you can see them glow red if you have them where you can see them and the load is high enough. like on a dyno.
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Might be a good idea.
I think such a car would also benefit from an after-shutdown oil- circulator, which keeps oil moving through the turbo bearings to prevent coking untl the bearings cool down a bit. The turbo may already have such a device.

No idea. My Integra has no fan timer. I shut down the ignition, the fan stops.
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