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1999 Outback Limited 5MT
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Discussion Starter #1
I looked around and didn't find anything so I started this in hope to find anwsers and know the differences between outbacks.

Like for a start I once drove a 97 legacy outback (leather, heated side mirrors, headlight flash with remote lock, etc) that was detailed nicely. When I first drove it off the lot from a used car dealer it was fine after about a few miles it started to over heat. Well I noticed that both fans were going. After I fixed the reason why it was over heating (thermostat was in upside down), I noticed that only one fan ran when it wanted to cool off (while engine was running) unless I ran the AC then both of them kicked on.

Now with my 99 legacy outback with a downgraded trim (cloth, no headlight flash with remote lock, no heated side mirrors, etc) I noticed that when the fans kick on to cool (while engine was running), both fan kicked on. I was confused why it was doing that but not concerned.

I know not all cars are the same but has anyone else noticed differences between other or similar outbacks that you may have owned or driven?
 

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Premium Member
03 H6 OBW & 06 WRX Sportwagon
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17,839 Posts
I think they went to 2-speed fans instead of a ' 1 at full speed, then 2 at full speed' system.

Someone once posted a chart of the logic used by tthe ECU to determine when and how many and what speed to run the fans. a little complex.
 

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1999 Outback Limited 5MT
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68 Posts
Discussion Starter #4
So according to the chart, when it's just idled and it gets to a certain temp, only one fan should kick on not both? So the 96 ran right but my 99 is doing something funny.
Hmmm, something to look into.
 

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There's three input variables in that chart: Vehicle speed, engine temperature, and whether or not the AC compressor is on. To verify the operation, the actual coolant temperature would have to be known. Of course, be sure that the AC compressor is off (and that the heater controls are not set to either of the two windshield defrost positions!)

Also, some time back when a similar question was raised, I recall that the function chart wasn't the same through each generation.

I believe it might, in part, be related to the flow of the radiator. For cross-flow radiators, the fans can be operated sequentially -- first one, then both if needed. For down-flow radiators, both will usually come on at the same time, but they can be in a high speed or low speed mode. (In cross-flow, all the coolant passes in front of both fans, so initially only one is turned on for low load situations, with the second coming on if necessary. In down-flow, with side-by-side fans, only 1/2 the coolant in the radiator is subjected to the airflow of each fan, meaning half the coolant isn't being cooled by a fan if only one is turned on. Consequently with down-flow radiators both come on, but at either slow or fast speed.

I'm not certain that is, in fact, the determinant, but it might be something to consider.

Let us know what you find . . . .
 

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03 H6 OBW & 06 WRX Sportwagon
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and often, the A/C is on in winter to help defrost/dehumidify.

also, as I said, some newer cars (dunno when it started) have 2 speed fans so the chart would be different.
 
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