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02 Forester
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51 Posts
Discussion Starter #1
Hello all. My '02's radiator fan is constantly cycling on and off, usually for very short periods (10 seconds or less). It starts as soon as I start up the car, whether it's 40 degrees out or 75. The engine revs drop noticeably when it cycles on. The engine seems to warm up normally and never gets over halfway on the gauge. Once the car is hot, the fan activity seems to be more normal, but still busier than I'd expect. So maybe this is normal, but my '98 didn't do it, nor has any other car I've ever had. Any ideas? I searched the forum but didn't see anything. TIA for all responses. PS moderators, if this would be better in the "Problems" forum, feel free to move it.
 

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2002 Forester S
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270 Posts
Is your heater/aircon set to window defrost mode? If so, that engages the aircon to make sure the air blown on the windows is dry by chilling it first to condense out moisture/humidity. IN that mode, the cooling fans will cycle on and off frequently.
 

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02 Forester
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51 Posts
Discussion Starter #3
No, it's probably been in every possible mode including no fan or a/c at all and it still cycles. It does sort of mimic the a/c compressor though, in that the engine revs slow down a bit with the added load. Resetting the computer didn't change anything. Oh well.
 

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71 Posts
Should the main cooling fan come on only when the AC is run or when the car reaches a certain temperature?
 

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2005 Forester XT 4eat
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4,583 Posts
Are the little green connectors under the dashboard connected? They shouldn't be.
 

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02 Forester
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51 Posts
Discussion Starter #6
Superhero, no car (or motorcycle) I've ever had has had the cooling fan come on before it's needed.

Guroove, I feel like I'm being set up here :confused: but what little green connectors?
 

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The Modfather
2019 Impreza 5dr Sport - Manual
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8,052 Posts
Should the main cooling fan come on only when the AC is run or when the car reaches a certain temperature?
The fans will kick on with the AC and or when the car reaches a particular coolant temp. The AC will come on even if it's cold outside when you turn on the defrost. Also, if you are on the hairy edge of needing a recharge in the AC system it may be cycling on and off due to that. (maybe) There is a pressure sensor that when it sees low pressure in the AC system turns the whole system off to protect it from damage. The system not only circulates the R134a but also lubricant so if it runs while dry bad things could happen.

The green connectors under the dash, look here:

http://www.subaruforester.org/vbulletin/f77/why-green-plug-not-connected-26518/
 

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1997 Murtaya !!
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1 Posts
That's fixed it

I'd like to thank those who posted here as i have just fixed the problem of the cooling fans cycling on the Forester just recently purhcased from Ebay !

The other forester i had has now become a Murtaya , and that's receiving a new gearbox which should be longer in the leg than the origonal.

Many Thanks

David
 

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02 Forester
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51 Posts
Discussion Starter #10
The fans will kick on with the AC and or when the car reaches a particular coolant temp. The AC will come on even if it's cold outside when you turn on the defrost. Also, if you are on the hairy edge of needing a recharge in the AC system it may be cycling on and off due to that. (maybe) There is a pressure sensor that when it sees low pressure in the AC system turns the whole system off to protect it from damage. The system not only circulates the R134a but also lubricant so if it runs while dry bad things could happen.

The green connectors under the dash, look here:

http://www.subaruforester.org/vbulletin/f77/why-green-plug-not-connected-26518/
In my case at least, AC not on, no defrost, car cold, AC seems great when I use it (and I do 1x/month for maintenance reasons), assume green connectors aren't (no other issues as described in thread), fans STILL cycling :confused:
 

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2010 Forester XT Limited AT
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316 Posts
In my case at least, AC not on, no defrost, car cold, AC seems great when I use it (and I do 1x/month for maintenance reasons), assume green connectors aren't (no other issues as described in thread), fans STILL cycling :confused:
Ever figure out the problem?
 

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02 Forester
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51 Posts
Discussion Starter #12
Nope. I've just grown to accept it as a quirk. The car has so few problems that I guess I shouldn't manufacture any.
 

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2010 Forester XT Limited AT
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316 Posts
I noticed my 2000 L doing the same thing the other day while parked in the cold with the heat on. Guess i will ignore it as well:crazy:
 

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Banned
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657 Posts
It's one of two things.

1. Engine thermo fan temp sender is the wrong one for your model!

2. Cooling system thermostat is failing, blocked or damaged!

If it's the engine water thermostat failing to open at the correct temp! It's opening and closing way too late causing the fans to cycle at that opening temp.

It will eventually break apart and close shut giving you an immediate boil situation!

Watch it! You can cook your motor when it fails!
 

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02 Forester
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51 Posts
Discussion Starter #16
Georgie,

I could easily believe that there is a problem with the sensor. I seriously doubt that it has anything at all to do with the thermostat. For one thing, as I noted, it happens when the engine is stone cold. For another, it comes up to temperature perfectly every time and the gauge never varies from its normal reading. But thanks for the input.
 

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2000 Forester Manual
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38 Posts
Old thread but...

I connected the green plugs thinking the PO disconnected them:eek:

What's the point of those plugs?
 

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99 Forester L
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93 Posts
For what it's worth, mine developed a problem where once it got so cold out, the fan would come on after a few minutes of driving and run continuously for the remainder of the time the car ran.
 

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2005 Forester XT 4eat
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4,583 Posts
Old thread but...

I connected the green plugs thinking the PO disconnected them:eek:

What's the point of those plugs?
They're for diagnostic use. They should be left disconnected.
 

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Registered
2002 Forester S 5 Speed AWD
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1 Posts
Relieved! So glad I found this thread!

It probably came up first because PDSF you described what the cooling fan in my newly purchased, and otherwise Perfect, 2002 Forester S with 180k on it does, So Exactly, that if I put quotes around my search, it's the Only link that even comes up!
Aside from this worrisome "quirk", I have had no reason to be anything but thrilled by this amazinly clean and perfecly kept, awesome little one owner car so far, for under $5k! In the middle of Winter 2014! One of the worst Ever no less!
I'm finding the same is true in that it never actually gets hotter than what I would consider the perfect operating temperature, despite the fact that everyone I've described this to, along with myself, and now all these other people, have considered this something to be concerned about.
Thanks for coming back and adding the note that it just seems to be the normal function. It pretty much takes away any more worry about it so I can just enjoy what I consider a Winfall that because of course, now that I'm prepared, has also apparently exempted the PNW from the hellish winter that's brought half the country to a standstill!
 
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