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2003 Outback LL.Bean H6 3.0 (aka: RubySue)
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48 Posts
Discussion Starter #1
ok, so the only other problem with my beautiful H6 is that sometimes the A/C goes out.... brand new a/c lines ... idler pulley and fresh freon charge...
and she blows cold as ice... but on occasion it will blow and blow without kicking on the compressor... Only fix is pulling over....turning the vehicle off. Then back on...and the A/C usually comes right back on...

am I looking at a bad A/C pulley here?
 

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The compressor on the H6 has a revolutions sensor; it detects compressor rotation when the compressor clutch is supposed to be engaged, and the signal is compared to the engine revs by the engine control module. If the compressor isn't rotating at the proper speed, the ECU will cancel the clutch engagement, and will not reset until the engine is turned off and restarted.

Sometimes the problem is the sensor itself; sometimes it could be a loose/slipping serpentine belt. I doubt the compressor pulley itself is bad, but the H6 also has a known problem with the tensioner pulley bearing. It could cause the belt to not be as tight as it should be.

Do a search here for revolution sensor, or compressor sensor; there's quite a few discussions.

Can't be certain that this is what's happening, but the symptoms are similar.
 

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2003 Outback LL.Bean H6 3.0 (aka: RubySue)
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48 Posts
Discussion Starter #4
looking into it a bit further I am now confused....

I see a TSB for the 2001-2002 Outback all models having the revolution sensor problem...
Cannot find anything on the 2003?!?!
I have been unsuccessful in locating a part number or TSB for the 2003....

help?!
 

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03 H6 OBW & 06 WRX Sportwagon
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17,572 Posts
I guess you've looked for a dirty cabin air filter? Blocked airflow might lead to icing or ?????

you could also charge the system with some of the dye infused refrig. If it's losing refrig. You could have a pinhole leak in the condenser from a rock-strike.

I just charged mine this weekend. Didn't swap any o-rings out but I'm prepared too if the dye indicates it.
 

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2003 Outback LL.Bean H6 3.0 (aka: RubySue)
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48 Posts
Discussion Starter #6
Heres the thing....all a/c lines have been replaced in the last 90 days.
same with the belt tensioner pulley....and recent charge on refrigerant.

The a/c works great most of the time...
When it stops blowing cold air I just pull over...turn the vehicle off.
Restart .. and BAM... cold air again....

Same symptoms as the 'revolution sensor' in the 2001-2002
but there is no TSB anywhere for the 2003.
no notes or mention at mysubaru.com
and I cannot find a part # or anything really on it for the -03

quite aggravating...
 

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The fact that there isn't a relevant TSB doesn't preclude it. There's a rear wheel bearing TSB for 2005 and 2006 Outbacks, (by model year and VIN) -- this of course doesn't mean other Subarus don't have wheel bearings, or bearings that could fail, like any other part.

Again, this doesn't mean that your problem is due to a defective rev sensor; for that matter, that your car even has one. But as noted, the symptoms are similar to that described in the TSB.

There was a thread here not too long ago where the AC was cycling, and replacing the compressor relay seemed to correct the problem. (I don't recall if it was a 4 or 6 cylinder.) But it reminds me that there's a possibility that a defective relay could lead to the same symptoms. If the relay doesn't provide a super good connection to the compressor electromagnet, the clutch won't be pulled in as strongly as it should and perhaps could slip. If it slips, the compressor rotation speed detected by the revolutions sensor (on an H6 so-equipped) could be less than the ECM expects it to be based on engine rpm, and it turns off the compressor.

The AC relay should be in the fuse box in the engine compartment. Probably worth trying if it hasn't been tested or replaced recently -- I think the relay costs less than $10 at dealers.

(I should have remembered the relay earlier. See my thread: http://www.subaruoutback.org/forums/66-problems-maintenance/26903-red-dust-behind-compressor-poor-ac-performance-check-ac-relay.html)
 

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03 H6 OBW & 06 WRX Sportwagon
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^^^good post

if the off-on trick gets the system going again, to me, it seems it must be the relay or the rev sensor. I suppose some very weird intermittent issue with a pressure sensor could fail this way - not sure.
 
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