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Car issue question

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speedin
Posts: 731 - Karma: 131
Just bought a 09 honda crv awd with 65k miles on it.
Runs great. It is completely up to date on all its service. Coolant is full and looks good.

However, I am stumped with this one issue. I am pretty mechanically inclined when it comes to cars. Have built a few motors in the past, so I am not totally in the dark. There are many people that have far more knowledge then I do. Which is why I am posting this thread. I have had no luck on some other forums posting this question. I know there are some mechanics here.

So the other day it got cold here. I decided to turn the heat on. That is when I noticed the radiator fan cycling on and off every 15 seconds or so. When I turn off the heat off it stops. Turn the heat back on, and boom it starts cycling on and off again. I know when you run the A/C that as soon as the compressor kicks in, the fan usually turns on as well.

But why the fan is turning on when using the HEAT is beyond me, and also why is it cycling on and off every 15 seconds.
Oct 30 2014 1:22PM
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howlongcanausern
Posts: 4982 - Karma: 1,737
you have your defrost on. when your defrost is on, so is the AC, hence the fan cycling.

does the fan still cycle when there's no defrost?
Oct 30 2014 1:29PM
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howlongcanausern
Posts: 4982 - Karma: 1,737
oh, and to answer your 15 sec question: the fan is programmed to kick on at a certain temp, so since it's nice and cold out the radiator is cooling down the coolant pretty quickly, so it kicks off quickly. since you're sitting still, the engine warms back up quickly, and the fan kicks off again.

also, this is an electric fan, correct? then why worry?
Oct 30 2014 1:38PM
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speedin
Posts: 731 - Karma: 131
momsspaghettioh, and to answer your 15 sec question: the fan is programmed to kick on at a certain temp, so since it's nice and cold out the radiator is cooling down the coolant pretty quickly, so it kicks off quickly. since you're sitting still, the engine warms back up quickly, and the fan kicks off again.

also, this is an electric fan, correct? then why worry?



The defrost is not on. Just the heat. Once I turn the heat off it stops. Basically acting like I have the defrost on or the ac.

It's annoying to hear, and doesn't make any sense.
Oct 30 2014 3:07PM
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tronned
Posts: 1098 - Karma: 790
seems odd. when you activate the heater flaps in the heater box, the actual heating aspect of the circuit does not change. The heater core is always working as a heat sink in the back of your dashboard... when you activate heat via your controls, all you do is change the routing of the flaps in the heater box to direct hot air to your blower motor instead of cool air from your evaporator.

Like mentioned earlier, if you choose the defrost setting the a/c compressor becomes active which in turn creates rad fan action. The whole premise of running rad fans when a/c is active is to pull more air over the a/c condenor which is located just infront of the coolant rad the front of the car. with the rad fans running the condesor gets saturated and cannot actually perform its cooling requirement.

You had mentioned you did not have defrost active at the time the fans cycle? If you have a control unit where you can control where the airflow is directed, point it only out of the vents facing passengers and if possible. There could be a strategy from the body control module to run the compressor if either the lower or windshield facing vents are selected. Also, have you confirmed that the fans only run on max hot and max cold? Try to find out where the line is that the fans become active. Some engines also have cooling circuits for there alternators when under heavy electrical load but I doubt the CRV is one of those cars. Quite a few Ferrari have a coolant line that circulates around the wire windings in a alternator so it does not melt under load.

Hopefully this helps, let me know if you have any luck or have any more questions.
Nov 1 2014 1:24PM
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